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History of US Tanks.


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Ok so let's start another interesting topic. US Armor is actually my black horse, and it's a very interesting story in itself, however and funny enough sometimes not very well known to general public, and sometimes shrouded by myths.


So where we start, I think the best is to start with M1 and then move to the other vehicles some more, some less obscure.


However here I will not talk about FCS of M1's, simply because we can all check it out in Steel Beasts, but focus more on it's development history, design solutions and some upgrade proposals.


Also there are some former and/or current M1 crew members, please if I will make any mistakes, give me a hint. ;)

So let's start, as we know the XM1 program started after the failure of MBT-70/KPz-70 program and it's simplified US variant XM803, but this is entire different story in itself, worth separate post.


Initially Congress provided 20mln USD for development of new tank, and in February 1972 in Fort Knox was created MBTTF - Main Battle Tank Task Force under command of General Major William R. Desobry, MBTTF primary function was to create initial requirements for new vehicle, to support MBTTF TACOM involved their advanced concepts unit which resulted in choice of first 8 initial concept projects prepared by J.B. Gilvydis. First 3 concepts were sended to MBTTF and 5 other were sended to Main Battle Tank Project Manager’s Office in the time period between February to August 1972 and were completed in March 1973. Also commander of Army Materiel Command General Henry A. Miley Jr. showed great enthusiasm for the project in his letter to Department of Army.


For vehicle development two companies were choosen, General Motors and Chrysler Defense (later known as General Dynamics Land Systems), and here it starts to get interesting, initially GM was ordered to research a possibility for further development of a new tank based on experiences and technology gained with XM803, while Chrysler was ordered to research a potential evolutionary development from the M60 lineage.


Initially program received designation XM815 but soon it was changed to XM1, the development work also was fast, first results was presented to MBTTF just 25th February 1972, and first concept design was codenamed LK 10322, which was a conventional design with driver compartment in front, turret in center and engine compartment in the rear.


At this stage the project was focused on researching possible protection solutions against various threats, as much as 14 different combinations of various design solutions were presented with various armor thickness, different armor materials, armor designs, vehicle dimensions and weight, in the end vehicle weight could vary from 34 metric tons to 57 metric tons, and protection could be provided against 23mm AP ammunition allaround and against 120mm HEAT ammunition from the front.


Armor development was done by Ballistic Research Laboratory, and here a bit funny bit, the development of various armors was so fast that both armor designs and vehicle designs were changed constantly to adapt these new technologies.


Open was also question of engine, two engines were considered seriously in the end, the AGT-1500 gas turbine and AVCR-1360 diesel.




What is interesting is that first drawing of the LK 10322 shows the tank being powered by AGT-1500.




Other thing we can notice is also some sort of special armor protecting turret and hull front. There is also a commander panoramic sight with remote weapon station armed with 12,7mm machine gun, it was design very ahead of it's time. However at this point there was no ammunition isolation in separate ammunition magazines with blow off panels.


There were also attempts to reduce vehicle weight and depending on variant engineers were able to reduce weight from nearly 3 to around 3,5 metric tons. Also lenght of hull was later increased by 685-698cm which would allow to increase fuel storage from 1135l to 1324l, and would only increase weight by around 272kg. This type of lenghtened hull could contain two types of powerpacks, the AGT-1500 with XHM-1500 transmission or AVCR-1360 with X-1100 transmission. 20th June 1972 MBTTF asked TACOM to create 3 analyzes concerning vehicles protection and weight in 72 different combinations (sic!) which were earlier created for modified LK 10322.


MBTTF also made a specific list of components that were part of these 72 combinations.



105mm Rifled Gun M68.

110mm Rifled Gun (British Design)

120mm Smoothbore Gun (German Design)


Fire Control System:

Modified FCS from XM803 but without commander panoramic day/night sight

Modified FCS from M60A1 with integrated day/thermal sight


Engines and Transmissions:


AVCR-1360 with X-1100

AGT-1500 with XHM-1500-2

DB1500 (later known as MB873) with RENK HSWL-354



Torsion bars





Alternative Diehl tracks

New lightweight tracks with witdh of 71cm.


Studies were perfomed in two ways, first was done to calculate armor weight and it's protection levels within vehicle weight limits, there were several weight limits selected, 43, 45, 47 and 49 metric tons, second was to calculate vehicle weight in each of 72 selected design combinations within a single tight protection level requirement. It was concluded that most optimal protection level would be for vehicle frontal arc a 115mm APFSDS from 800m and 81mm shaped charge warhead.


Ok here will be a controversial theory from me. The above protection requirement was before US intended to use new special armor developed by British within "Burlington" program, it was intended for original US developed armors at the time. So a good question is if someone just didn't used these requirements to later describe protection levels offered by BRL-1 armor package used in original M1, which were secret, and most likely higher because vehicle was also in the end, heavier than it was in original requirements. Food for your thoughts.


Besides original 72 configurations, additional 15 were made, configurations numbered from 73 to 80 were transferred for further work to General Motors, while ones with numbers 81 to 83 to Chrysler, while the ones with numbers from 84 to 87 were projects of improved M60A1. Also MBTTF from 72 configurations, eliminated ones which included use of the British 110mm main gun, mainly because in MBTTF opinion, it did not presented significant improvement over 105mm, also projects armed with German 120mm gun were eliminated, mainly because at the time MBTTF expected it not be ready within required time.


What is also extremely interesting is at this stage, also projects with AGT-1500 gas turbine were eliminated, as it was considered as too risky compared to a diesel. This meant that from original 72 combinations only 16 were left, and these 16 combinations were different only in used engines, transmissions, fire control systems and other minor equipment.


In the end it was decided to use only AVCR-1360 engine or DB1500 (from Daimler-Benz company, later taken by MTU when engine changed it's designation to MB873), also then another problem emerged, the weight and protection requirements were contradicting each other, in such situation MBTTF proposed AMC two solutions, first was to just loosen protection requirements, second was to loosen strict weight requirements, in the end it was decided it's better to sacrifice lower weight and keep greater protection levels.


In July 1972 TACOM received another design proposal codename LK 10352 it received new redesigned hull, especially it front, the lower front plate was angled at 60 degrees, the upper angled at 65 degrees, and it seems both contained some sort of special armor, also turret was of new design.




Weight of such vehicle was calculated to be 52 metric tons with required protection levels of frontal arc against 115mm APFSDS from 800m and 81mm shaped charge warhead. In August and September project was again modified, this time with armor only, and here interesting thing in the source material, it's said that this special armor used was sort of glass in between steel plates, which says it was most likely Silicieous Core Armor developed in the past for XM60! And later this armor was replaced by new design made by BRL which included multiple layers of steel and aluminium.


BRL also provided armor for tests, and tests were performed against 3 levels of threats, level 1 also called light, was 115mm APFSDS from 800m, level 2 called medium was 115mm APFSDS from 800m + 81mm shaped charge warhead, level 3 called heavy was 115mm APFSDS from 800m + 127mm shaped charge warhead. This last level was later choosen as pattern of threats against which new tanks armor must provide protection during later studies.


Again problem was encountered when wood mockups in 1:1 scale were intended to be build, BRL was sending new armor designs such quickly that TACOM personell could not keep up with constant redesigns in turret and hull shape. Also at that time it was decided to develop two final concepts for isolated ammo storage, and here also there were several concepts, one of them intended to use automated 18 rounds turret bustle magazine (isolated of course) and the rest would be stored in two rotating drums in hull on both sides of the driver, and these magazines would also be isolated, all magazines would be isolated with 25mm aluminium bulkheads with small ammunition ports. Additional 6 round ammo box was placed on turret basket floor, made from 63mm thick armor plates. Later design was changed to what we know from the original M1.


Now something about the main gun, it would be 105mm M68 rifled gun, however, important thing to note, this gun is not, and I repeat it's not a license version of the British L7. M68 is a series variant of the US made T254E2 105mm rifled gun, however due to US/UK agreement both guns can fire the same ammunition, have interchangeable barrels, and  during development period, both started to share the same, British designed bore evacuator, this is why externally both look so similiar, but inside, they are completely different.


Additional armament would be coaxial 7,62mm M73 and 12,7mm M85, there were also some ideas to install 25mm automatic cannon Bushmaster, in the end however it was eliminated so main gun ammo storage was increased to 55 rounds. What is interesting at some point, engineers also considered to install 2 TOW launchers on the turret sides.


Let's back to the vehicle armor. During and after Jom Kippur war, NATO started to receive data from IDF about the use of new Soviet anti tank weapons, it was a final proof that conventional armor will not provide sufficent protection, while BRL designs were not completely satisfactionary, however at that time US and UK were already in talks about new British invention, or rather I should say, inventions. To clear something out, within the program codenamed "Burlington" not single special armor model was made, but several, some of them very exotic, declassified documents talks for example about special armor with integrated explosive reactive armor layer. Also these armor didn't had any codenames, codename was used only for development program, while armors were called simply "Special Armor no.1" or "Special Armor no.6" or simply as "Buiscuits" no. 1 or no. 2 etc. So apllying both codenames like "Burlington" or "Chobham" to these armors, is not entirely correct.


So about the armor itself, actually it's descriptions provided for general public in the past were clever disinformation, considering what can be find in declassified British documents. Descriptions for public said that armor was combination of steel, ceramics and similiar exotic materials in a passive form, now we know that this armor was actually more similiar to NERA - Non Energetic Reactive Armor or NxRA - Non Explosive Reactive Armor, where there are layers of steel or other materials with reactive non energetic/explosive layers in between them.


About the US and UK armor development programs, I can only provide two excellent article by Polish historian Paweł Przeździecki, links below:

http://wceo.com.pl/images/Dokumenty/WBBH/PHW/PHW_3_2011.pdf -> PDF reader page 112.


http://wceo.com.pl/images/Dokumenty/WBBH/PHW/PHW_4_2011.pdf -> PDF reader page 106.


Both are unfortunetaly in Polish only, you can try to use translator, however author provides all sources he used, so if anyone can, he can search for them himself.


Now let's return to prototypes, we know that even if gas turbine was considered as a risk, Chrysler chief engineer dr Philip W. Lett decided to take that risk, there were some good reasons for that, first the torque and power of gas turbine in very compact package, so more weight could be saved for something else... for example more armor. Another reason was that gas turbine is trully multifuel, so no problems with loosing too much power when switching to a different fuel or problems like with Leyland L60 diesel used in Chieftains. I am sure there is more to that story, but up to this day it's all a bit shrouded in mystery, what standed behind some decisions.




GM prototype was still tested only with AVCR-1360 diesel, however, and this is not widely known, Chrysler prototype also could change engines, it was both designed for gas turbine and diesel. There is actually a drawing showing vehicle in slightly later prototype phase, which shows two final configurations with two different hull configurations, one for gas turbine and second for diesel.



So from left to right we have mid prototype, then late prototype in the middle, this one also with gas turbine, and in the right there is late prototype with diesel.


After series of trails GM prototype was discarded and superior Chrysler prototype was selected for further work.


In december of 1979 also Leopard 2AV was accepted for trails, it's a story in it's own right, so I will only say that Leopard 2AV did not meet requirements considering armor protection and crew safety/survivability, or in general XM1 meet all major requirements, Leopard 2AV meet all minor requirements, besides XM1 was cheaper, it costed only about 750K USD back then compared to 1mln USD of Leopard 2AV.


Final tests of XM1's armor protection as well as internal crew safety/survivability meassured were done during Development Test - II with prototype PV 11, it was fully loaded with ammo and fuel, and dummies were placed in crew positions, and later at various ranges the tank was hit by various types of armor piercing munitions. These tests were complete success, the tank was not only not destroyed, but also was able to move under it's own power from the test stand, may 7th 1979 XM1 was approved for service and 110 low rate initial production vehicles were ordered, two first vehicles taken part in ceremony when they were named by the then SecDev in honour of General Creighton W. Abrams as M1 Abrams.


However some problems were found with these LRIP vehicles, there were problems with air filters, which resulted in damage of the engine during Operational Tests - II, also due to hurry and lack of quality control, engine manufacturer provided several faulty engines, also problems with throwing tracks during drive in mud were found, but quickly solved by simple retainer rings on sprockets.


Another interesting problem was encountered with welding, or rather lack of qualified personell in welding of entire turrets and hulls, simply because in the past vehicles were made from large castings or smaller casting welded together, not high hardness rolled steel plates welded together, this problem however was also quickly overcome.


February 19th 1982 Chrysler Defense was sold to General Dynamics and renamed General Dynamics Land Systems, however chief engineer dr Phillip W. Lett stayed and continued his work on further development of the M1.




On this photo in the center to the left we can see chief engineer dr Phillip W. Lett in front of one of the LRIP M1's.


Ok I think it's enough for now, let's call it part 1, it's getting late and this post starts to take huge size. However stay tuned for more, and as always I hope this bit of informations is interesting and also entertaining for all of you guys. ;)


* My primary source of information is R.P. Hunnicutt „Abrams A History Of The American Main Battle Tank volume 2”, I strongly recommend this book as it's fantastic source of information about M1's development and what happend before it. I also strongly recommend other fantastic books of this author.



Edited by Damian90
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Ok so perhaps let's take a short detour from history to the M1's armor protection.


Let's first talk about some differences in turrets and hulls between specific major versions, during my own research I made a classification for these just to make things easier.


So let's start with the turrets:


Type 1 "Short Turret", used only in original M1, it have thinner frontal armor that have effective armor thickness ~700-750mm, and a bit different roof over turret bustle with 3 cutouts for blow off panels.

Type 2 "Interim Long Turret", used only in M1IP variant, have thicker frontal armor, effective thickness ~800-900mm (Steven Zaloga in one of his books said that armor thickness was increased by ~200mm), no other structural changes.


Type 3 "Long Turret", this is the final turret variant used in M1A1 and M1A2, older turrets can't be upgraded to this variant due to significant structural changes thus all these turrets are new builds, even if M1 or M1IP was upgraded to M1A1 or M1A2 standard. Front armor effective thickness is also ~800-900mm.




Type 1 used in M1 and M1IP, it lacks the overpressure NBC protection system, probably have some minor differences with the next type. Front armor effective thickness where special armor is mounted is ~650-700mm and did not changed till this day.


Type 2 used in M1A1 and M1A2 variants, major difference is that overpressure NBC protection system is present, some other minor differences are present depending on tank variant, Type 1 hulls can be upgraded to Type 2, however it requires complete disassembly, cutting and welding in some places.





The upper glacis plate and driver hatch effective thickness is ~50mm and is angled at ~82-85 degrees which gives it effective thickness of ~359-573mm, hard to say at what exactly angle glacis plate is.


Hull sides over crew compartment are a steel composite, probably something like 40mm + 30mm or 40mm + 40mm which gives effective thickness of ~70-80mm and it's probably made from different types of steel, the base is most like RHA while addon plate is HHS, while engine compartment is protected only by 40mm of RHA armor. Heavy side skirts are ~70-80mm composite type, light side skirts are ~5-10mm thick. Hull rear is also probably ~40mm thick.



Now about special armor itself, there were several types used:


BRL-1 (1980) used in original M1.

BRL-2 (1984) used in M1IP and M1A1.

HAP 1st generation (1987/1988) used in early production M1A1HA.

HAP 2nd generation (1990) used in late production M1A1HA as well as new M1A1HC and M1A2.

HAP 3rd generation (1999/2000) used in M1A1SA, M1A1FEP, M1A2SEPv1 and M1A2SEPv2 (there is possibility of some upgrades for this armor in 2010+ period of time).

NGAP/NEA (2017+) used in newest M1A2SEPv3.

EAP (?) used in all export variants for Arab states.


*BRL stands for Ballistic Research Laboratory, these were designations of lighter and heavier armor variants based on British research, that were developed by BRL in US, it's assumed that BRL-1 was for original M1, while BRL-2 was improved, heavier version for M1IP and M1A1. HAP stands for Heavy Armor Package that uses components made from depleted uranium alloy, we know that there are at least 3 generations of this armor, there is also special variant for Australia where depleted uranium was replaced by something else, perhaps tungsten alloy, but Australian documents I found suggest that it's protection levels are equal to 3rd generation Heavy Armor Package, originaly it was said this type of armor is used in turret front only, however I found mentions in official sources saying it is used also in hull front and turret sides. EAP or Export Armor Package is meant for non NATO/Close allies (like Australia) of the US, used in tanks provided to Arab states, some theoretize it might be equivalent to BRL-2 but it's probably heavier and offer better protection, but lower than HAP armor package.

One more important thing to note, today we also know that at least the newest M1's also uses Titanium alloy in their armor and several other components.




There are also two types of serial numbers. One for the turret, and one for the hull, serial numbers on turrets says us what type of armor vehicle uses, and on the hull where it was made. X will equal digit.



XXXX - BRL-1 or BRL-2 armor package.

XXXXU - Heavy Armor Package.

XXXXM - Heavy Armor Package (some US tanks have it, don't know why that change in letter).

XXXXA - Heavy Armor Package variant for Australia.

XXXXE - Export Armor Package for Arab states.




XXXXD - Tank was made in Detroit Tank Arsenal.

XXXXL - Tank was made in Lima Army Tank Plant/Joint Systems Manufacturing Center.


When it comes to armor itself, today we know it is indeed some type of advanced NERA or NxRA armor, however we only know more or less the structure of the turret side armor, and still only of older variant probably M1A1HA or M1A1HC.




This is how probably turret side armor over crew compartment looks like.




And this is how turret bustle side armor looks like.


And it makes sense, on one of the photos we can see some turrets after armor replacement/upgrade work in Joint Systems Manufacturing Center Lima, Ohio. We can notice that their frontal and side armor was replaced, but turret bustle was untouched.

With such evidence we can assume that turret armor is only replaced over crew compartment, while turret bustle armor might be untouched, and it makes sense from armor protection distribution point of view, where majority of protection increase and thus weight increase we want around the crew and for vehicle frontal 60 degree arc.


Here some more sources.


And here US Army Weapons Hand Book 2016.


At page 14 in PDF reader we can read for M1A1SA and M1A2SEP "Survivability improvements include frontal armor and turret side-armor upgrades.", of course term "frontal armor" means most likely both turret and hull, and we have confirmation of side turret armor upgrades. And it also seems that M1A1SA and M1A2SEP shares the same armor type, which makes sense because due to reduced costs, simplicity etc. at one specific time you manufacture only one specific type of armor and it makes sense for MBT's even in various but not that much different variants to share the same armor protection. USMC M1A1FEP is also technically equivalent to US Army/ARNG M1A1SA with some minor differences, thus it's safe to assume that it also shares the same armor.


Another thing is that M1's armor, like all modern 3rd generation MBT's armor is modular or semi modular, which makes it's replacement or repair relatively easy, quick and cheap. Another factor is that M1's turret and hull have very simple geometrical shapes making both manufacturing relatively simple, quick and cheap, as well as armor replacement/repair will be such relatively simple, quick and cheap task.


This also means that frontal protection is uniform for both hull and turret, and have very small weak zones.




Some additional protection over hull front is added by massive fuel tanks (visible on one of the drawing above), Israeli data says that 70mm of fuel is equivalent for 10mm of armored steel, thus we can assume that front hull protection where fuel tanks are is significantly increased.


However the largest improvement in protection will be made in M1A2SEPv3, photographs of one of the 9 prototypes shows us vehicle with massive weight simulators on turret front and hull front. This prototype still uses 3rd generation HAP armor package because it was originally M1A2SEPv2 converted in to M1A2SEPv3 prototype.


Each turret cheek have 4 welded plates, each looks to be ~50mm thick at most. Hull front have 3 welded plates, also each looks to be ~50mm thick at most. This means very significant weight increase over the previous generation armor, so we can assume also very significant protection levels increase over the front.


Some additional informations about vehicle survivability improvements can be found here.


Final armor protection improvement are M19 ARAT-1 and M32 ARAT-2 Explosive Reactive Armor modules.


M19 ARAT-1 is modern, multilayer explosive reactive armor, which might have some sort of anti-tandem warheads capabilities.


From these photos we can see angled layers of ERA inside the module, and perhaps some sort of passive component?


Also to M19 modules, can be attached M32 modules.



It's very unusual design for ERA, and it's interesting it can be combined with M19 modules in to a single, multilayer type of ERA protection. M32 modules can also be attached alone to the turret sides.


In such configuration both turret and hull sides have very good, right ERA cover. The system is modular and can be arranged per need.

Of course besides it's armor M1 have other survivability meassures, primary one is mentioned earlier complete isolation of the main gun ammunition storage. It needs to be noted that the biggest tank and crew killer is not the enemy ammunition penetrating the armor but own ammunition cooking off.

The original M1 and M1IP had such ammo storage:

Turret bustle ready rack - 22 rounds.
Turret bustle semi ready rack - 22 rounds.

Turret basket floor armored box - 3 rounds.

Hull ammunition rack - 8 rounds.


M1A1 and M1A2 have such ammo such ammo storage:


Turret bustle ready rack - 17 rounds with old type of racks and 18 with new type of racks.
Turret bustle semi ready rack - 17 rounds with old type of racks and 18 with new type of racks.

Hull ammunition rack - 6 rounds.


In future another upgrade that will increase M1's already fantastic protection and survivability will be hard kill active protection system, however and it's not widely known, M1's had in the past, but not used often a soft kill active protection system or actually two, the AN/VLQ-6 and AN/VLQ-8, both are sort of IR dazzlers which work similiar to Russian Shtora-1 and Ukrainian Varta.



It was seen used only on M1A1 variants, and in combat only by USMC.

Ok that's enough, in the next we will return to the vehicles history and further development.

Edited by Damian90
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On 21.09.2016 at 9:39 AM, lavictoireestlavie said:

Beautiful rightup Damian !   Please keep it coming ! :)


Sure thing. By the way I edited previous post about the armor because I forget to mention about Titanium alloy used in it's armor, that we know today it's true, at least for the newest versions.


Ok let's maybe talk about armament, because here also are some myths. As I previously mentioned in my first post, the US M68, M68A1 and M68A2 105mm rifled guns, are not contrary to popular belief American license version of the British L7 105mm rifled gun. Both guns are completely separate developments, and the M68 is a more compact gun compared to L7.



This is M68, and indeed it is a very compact tank gun.


So we can compare here the size of M68 105mm in M60A3 and L7A3 in Centurion, of course M60A3 have more internal space but still the M68 is a slightly more compact gun.


And the same pattern will repeat itself with the 120mm smoothbore guns Rh120 and M256. Both guns are not interchangeable, you can't rearm Leopard 2 with M256 and M1A1/A2 with Rh120. The gun cradle, recoil system, gun breech and other components are different, however both guns can fire the same ammunition and have same or similiar ballistic properties, because both are based on the same technology.

And the same applies to other Rheinmetall type guns as we can call them, the Israeli MG251 and MG253 are most likely based on M256, but also are not interchangeable, there is also MKEK L55 120mm smoothbore gun, and here I have a some suspicions, it is L55 but the gun breech, cradle etc. are more similiar to M256 than Rh120/L55, so perhaps this MKEK gun intended to be used on Altay, and similiar gun used in South Korean K2, might be a further license development of the M256E1 L55 gun.


Let's take a look.

Here is a video, showing M1A2SEPv2 turret interior, take a notice on the main gun breech design.



Here is a photo.



And this is Turkish MKEK L55 120mm smoothbore gun, the breech design similarities with M256 are striking.



And this is Leopard 2, we can see there significant difference in gun breech design, and there is more like a different recoil mechanism, different cradle etc.

And here we can see South Korean K2, also bare in mind South Korean K1A1 and K1A2 tanks uses local license version of M256 known as KM256.


I also have a photo of M1A2 armed with, I think it's a M256E1 L55 gun, the photo is of bad quality and very small, but still confirms that such gun existed.




There is also a photo of the original M1, with a different gun, perhaps first experimental iteration of M256E1, and that original M1 was just a test bed for it.



Another newer development for possible M1 main armament is the XM360E1 120mm smoothbore gun. It's a further development of the XM360 120mm smoohbore low recoil gun for the XM1202 MCS light tank. And there is some interesting observations we can make from CAD models and official statements.






It's definately lighter gun, more compact than the previous generation guns. Also we know that XM360 was able to fire exactly the same ammunition with the same performance as M256, and here interesting bit, as we can see on screenshot, it is said, M360E1 compared to XM360 can fire ammunition with higher impulse and higher chamber pressure. Which means it's more pwoerfull gun than M256 or Rh120 or other comparable 120mm smoothbore guns. And it's kinda similiar to for example what Russians did with their new 2A82-1M 125mm smoothbore gun that can fire rounds at higher chamber pressure than previous generation 125mm smoothbores.

Another things we can note is that XM360E1 is longer without muzzle break than XM360. AFAIK XM360 had a L48 barrel, so this can mean that XM360E1 have L50 barrel, maybe longer, something like that. And another interesting bit about these guns are locking lugs, XM360 and XM360E1 have 6 locking lugs, compared to M256 or Rh120 2 locking lugs. Again suggests that these guns were designed with higher chamber pressure in mind.

We can also note that both XM360 and XM360E1 does not have reactive bore evacuator, so perhaps compressed air is used in both?


But returning for a moment to locking lugs, I found that 6 locking lugs is nothing new, actually it was present in some of the previous development like 120/140mm XM291 smoothbore gun and 155mm XM297E2 gun-howitzer for XM2001 Crusader.


XM291, photo is of bad quality but we can see more than 2 locking lugs.


Vide of XM2001 compared to M109A6, but we can clearly see breech of the XM297E1 gun-howitzer with the same pattern of 6 locking lugs as in XM360/XM360E1.

So what about the future? I found digging through various official US Army websites in various documents that, indeed, there are some consideration of replacing M256 with XM360 (or rather XM360E1), but what I also found interesting, they also consider using autoloader for the M1, and here it also starts to be interesting. There were two designs of autoloaders for M1A1 and M1A2. First was developed by General Dynamics and was codenamed FASTDRAW.



More about it can be read in ARMOR Magazine issue from 1995 page 18 in PDF reader.


In general I recommend to take a look at various issues of ARMOR Magazine -> http://www.benning.army.mil/armor/eARMOR/BackIssues.html

Another type of autoloader was developed by Meggitt Defense, and it's called Compact Autoloader. Unique feature of this autoloader type is a fact that it have two parts, it's automated magazine and the autoloader itself, and automated magazine can used without autoloader, so it would work the way that it automatically move selected round to the ammo port where human loader can take it and load it in to main gun.


Some other unique features of US made tank autoloaders like FASTDRAW or Compact Autoloader is that they can both load and unload the main gun, as well as their high ammo capacity compared to other systems. 

Ok so I think it's enough for now, to the next time. ;)

Edited by Damian90
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Let's talk now about somewhat less known history of the M1 development, it's specialized variants.


When the M1 was designed, US Army only had M88 and M88A1 ARV's avaiable, and these were inadequate to tow M1's that with each new version rapidly started to grown in weight, decision was made to upgrade M88A1, program was known as M88AX and later as M88A1E1 that led to the development of M88A2, however GDLS offered to design and build ARV based on M1 chassis from their own funds if the US Army would agree for fair comparision trails between it and M88A1E1, it was known as RV90 but I also found here and there designations like ARV90 or XM90. US Army initially didn't wanted to agree considering M88A1E1 as adequate and cheaper but Congress decided that both vehicles should be compared, first RV90 prototype was builded in Detroit Tank Arsenal in 1988.



RV90 had a crane able to lift 31 metric tons of weight, crew of 3, weighted 60 metric tons, had a space for additional 4 people (crew of disabled tank), and was able to drive as fast as 64 km/h.


As expected the general performance of the RV90 was superior to that of M88A1E1 during trails, however US Army decided that the winner was M88 and thus new variants was selected and standarized as M88A2.


Another variants that were actually fielded are M104 HAB (Heavy Assault Bridge) also known as Wolverine, and it's simpler less expensive variant JAB (Joint Assault Bridge).



HAB uses Leguan type bridge, while JAB reuses older type of scissor bridge, both will be in service, HAB only in US Army, JAB in US Army and USMC.


Another vehicle is engineering tank M1150 ABV (Assault Breacher Vehicle), originally designed for USMC, now also serves within US Army... what can be said more? Video tells it all.

However kinda uniquefeature of ABV just as HAB and JAB is that, these hulls can still be relatively easy converted back to a standard MBT configuration if needed, because space for the turret is still there, and the hull did not loose it's original shape.


Another engineering tank variant, this time designed as a completely new vehicle, was Obstacle Breacher Vehicle Grizzly, it didn't went in to service, tough it definately was a capable vehicle.


Another designs can be considered as even more unknown to the general public, they never went as far as I know beyond drawing boards but were non less interesting.


First is the Liberty SPAAG system.




Such model was builded presenting this system, that can be considered as initial approach for development of US equivalent to the Soviet 2K22 Tunguzka system.


Another is AGDS - Air Ground Defense System.



This one is a bit more tricky vehicle, because it should not be considered only as SPAAG, but more sort of M1 based tank fire support vehicle, like the Russian BMPT.

Finally the XM2001 Crusader with it's XM2002 ammunition carrier.


Both vehicles most likely survived and XM2001 (at least one, perhaps there were more prototypes that survived) is kept in some museum in US.


It's such a pity that XM2001 was cancelled just when it passed all state trails, was accepted for service and production line was ready, simply because Cold War ended, budget was cut, and some madness started which I will describe later. Even today XM2001 would be unmatched in it's capabilities.

XM2001 and XM2002 would share components with M1 MBT, like new gas turbine engine LV100-5, as well as new hydropneumatic suspension system. This supension system is still avaiable and considered as replacement for current torsion bars suspension system. Suspension is made by L3 and designated as 3870 series.



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4 hours ago, Fabfire said:

Outstanding post. Thank you! 


Thanks. :)


Now something short, but might also be usefull and informative. M1 series have in service 3 types of commander cupolas + there was proposal of 4th variation.


The first commander cupola is CWS - Commander Weapon Station, well known to SB players that plays with M1's, non stabilized, remote commander MG, 3x magnified day sight, 6x periscopes. Compact, simple design.


The second is ICWS - Improved Commander Weapon Station, first used in M1A2, it's even simpler design, commander MG is on flex mount and can be only manually operated, cupola can't rotate, it's fixed, but have larger periscopes, there is also more of them, 8 instead of 6 so visibility from the inside is better.


But someone would ask, ok but why in M1A2 CWS was replaced by ICWS? Well as far as I know, originally they wanted to keep CWS on M1A2 untill they started to install all additional electronics and especially commander CITV display and IVIS system display (IVIS was first BMS system ever fielded, and is ancestor to modern systems like FBCB2/BFT or JBCP), they discovered there is no space for CWS drives responsible for it's rotation, sure they could somehow move them, but that would probably require some cutting and welding, it was simply not worth the effort, time and costs, so they just replaced commander cupola.

CWS on the left and ICWS on the rght.


However real combat showed that it's better to have a remotely controlled MG for commander, than manually operated one that requires to expose commanders body to enemy fire. But still CWS is not stabilized, and it's optics are... well simple.


So the upgrades were going kinda two ways one way for M1A1 series, second for M1A2 series. So let's start with M1A1 series, the original cupola structure during upgrade was not discarded but reused through modification. Controls were simplified, stabilization system in elevation and azimuth was added, new day sight was added and also thermal sight, we will back to these new sights a bit later. Also additional ballistic protection for commander was added and a counterweight for massive stabilization system.


This is how SCWS - Stabilized Commander Weapon Station was created and it's retroffited to US Army/ARNG M1A1SA and USMC M1A1FEP.



On the second video you can actually see how stabilized is the cupola when commander uses it.

The USMC also decided they need to further upgrade this concept, so the old cupola controls will be removed, and now it will be controlled via commander control handle also used to control the turret, main gun etc. Thanks to this, ergonomics will improve and the cupola will become equivalent to commander panoramic sights like a CITV from M1A2 series or PERI from Leopard 2's, just armed with remotely controlled MG, and of course it will receive improved sights.



The question is do ARNG and US Army will also use this upgrade? Hard to say, US Army have only a single unit using M1A1SA's, 11th ACR which is the last US Army unit using M1A1 series, rest is completely rearmed with M1A2SEPv1 or M1A2SEPv2, and in 2017 upgrade to M1A2SEPv3 will start and US Army plans to upgrade it's entire active tank fleet to this standard.

ARNG on the other hand have only two ABCT's armed with M1A2SEPv2's, rest is using M1A1SA's, however, I seen through DTIC archives that ARNG is rather pushing towards complete tank and IFV fleet unification with US Army, which makes sense, so, probably no, they won't use this upgrade.

Ok so we have the SCWS, so what about ICWS? Was there a similiar upgrade, actually yes, they was demonstrated few years ago on one of middle eastern countries arms industry expo's, I don't know what was designation of the demonstrated proposal for ICWS upgrade but, I just called it for ease SICWS.



I must say it's a, elegant design, and I wonder why US Army never got interested in it.

Right now M1A2SEP's receive the M153 CROWS-2 system.


And it's not a bad system in itself, it have full stabilization, good optics, controls for it are very ergonomic inside the turret (I know I was inside M1A2SEPv2 ;)), the only thing I would agree to complain about it's size, not in tactical terms, because it's height might be actually usefull, for example in turret down position, but it kinda limits commander visibility from his cupola to the front.

This is why the new CROWS-LP (Low Profile) is tested for M1A2SEPv3, and indeed it's lower, maybe around 50% lower, and looks good, should have similiar capabilities, and should not limit commanders visibility to the front so much.


Also worth to add is, interesting photo of the M1A2SEPv3 turret demonstrator, showing upgrades and changes to the gunner and commander stations, displays are new, multifunction, electronics in general are more compact, lighter, takes less space, you can even notice that the entire sighting system was replaced with something new. It is said in some sources, forgive me I won't place it here right now, would need to seek it, but gunner will receive new day camera, new 3rd generation FLIR, probably also new LRF, and what was most surprising, same with commander CITV, it will receive a day camera now, 3rd generation FLIR, and also LRF, so it's will be significant upgrade to already great M1A2SEP FCS.

M1A2SEPv3 turret demonstrator compared to standard M1A2SEPv1/v2 turret.

From this photo we can also assume, that CROWS-LP will be fully integrated with tanks FCS because I do not see separate control handle for it, neither separate control box, so most likely it will be controlled via CCHA and a menu in the commander display perhaps?

Well hopefully next year first 6 production M1A2SEPv3's will be presented and, yeah, maybe they will also show their interior, and we gonna see how close they got to this turret demonstrator, or how much changed, or not changed compared to M1A2SEPv2. Time will tell.

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57 minutes ago, Furia said:

Awesome post Damian!!!

Thx. Keep them coming!


As you wish, but it's the last for at least now, I am tired. :P


So maybe a bit of observation, as I mentioned in my first post, M1 was initially designed to accept various types of engines, transmissions and suspension systems.


This makes the tank quiet modular.


So initially 3 engines were tested, AGT-1500, AVCR-1360 and MB873. Well these were not all proposals for the M1, what about 1500HP version of the AVCR-1360 ancestor, the AVDS-1790? Well, here it is:


Well, engine is avaiable, was there proposal to use it in M1? yes there was!


Something else? Well there is GD883/MT883 diesel engine proposal which is the most recent one:

This engine is actually considered as a part of ECP3 upgrades or as GDLS representatives like to say 3rd generation of engineering change proposals.


There were however two other engine proposals, the new gas turbine LV100-5 and diesel XAP-1000.

Above XAP-1000, below LV100-5, one must admitt these were very compact engines.

So in the end at leas 7 engines were designed and tested in the M1 chassis, it's kinda pity that AGT-1500 replacement was not choosen earlier but it's understandable, engine replacement costs a lot.


As for suspension, there are several variants of torsion bars suspension, the recent one is called 70+ tons suspension system, there was also tested so called Cadillac Gage In-Arm hydropneumatic suspension system, and of course L-3 3870 series hydropneumatic suspension system.

It's possible partially because of the very simple shape of the hull itself, with flat sides so installation of various suspension system is quiet easy. I suspect that if someone would wish to, it would be possible to install there even boggies based suspension system.

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This is the kind of solution I like...





I like the idea of the TC having a weapon of his own.  It doesn't matter so much weather that weapon is something like the M2 that's capable of engaging aircraft and lightly armored vehicles, or something like the M240 that the TC on the Merkava gets, so long as he has a weapon.


In Pro PE when I'm fortunate enough to have a human gunner, I typically don't ask him to stop engaging or searching so that I can fire my TC weapon.  If I fire mine at all it's typically to do recon by fire, or just to hose down areas where I suspect enemy infantry to be hiding in order to provoke a reaction if I can.


The thing is...The CROWS mount is just so damn big...It looks like a great tool for use in urban fighting, but I don't think you'd want it on top of your tank when operating in an anti-armor role...



It's too bad this never got produced...

Yes the US pretty much has always had air superiority over regions of ground conflict since the Korean war, but that may change some day.

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9 hours ago, Maj.Hans said:

I like the idea of the TC having a weapon of his own.  It doesn't matter so much weather that weapon is something like the M2 that's capable of engaging aircraft and lightly armored vehicles, or something like the M240 that the TC on the Merkava gets, so long as he has a weapon.


In Pro PE when I'm fortunate enough to have a human gunner, I typically don't ask him to stop engaging or searching so that I can fire my TC weapon.  If I fire mine at all it's typically to do recon by fire, or just to hose down areas where I suspect enemy infantry to be hiding in order to provoke a reaction if I can.


The thing is...The CROWS mount is just so damn big...It looks like a great tool for use in urban fighting, but I don't think you'd want it on top of your tank when operating in an anti-armor role...


Well CROWS is not that bad, sure it's not elegant, but think about it, if you are in turret down position, it provides you greater visibility than even CITV, and CROWS really have good optics, both day and thermal, is fully stabilized and have laser range finder, so it can be considered as second CITV.

When US troops were in Warsaw I actually noticed an interesting working mode, we know that CITV can be put in autoscan mode, right? Well guess what, CROWS also can be put in to autoscan mode, what's more commander can turn on view from both CITV and CROWS on his displays in the same time, so he can effectively and constantly be able to observe two different sectors, and third can be observed by the gunner.

It is very interesting capability that I didn't seen on any other tank.

Of course there is another solution I forgot to mention, the Raytheon Battleguard system.




It's too bad this never got produced...

Yes the US pretty much has always had air superiority over regions of ground conflict since the Korean war, but that may change some day


Yeah, tough I think US Army is fixing this, they will got modular AAD/ABM command and control system ICBS which will serve as command center both for Patriot system units and new MML launchers, so Patriot will be MRAD system and MML will be VSHORAD/SHORAD system depending on missiles it will use, and MML launcher can in single launcher combine different types of missiles.


The only thing US Army will need for it's AAD then is a proper SPAAG, tough putting such system on M1 chassis is IMHO excesive and too expensive, it's better to place it on something smaller and cheaper like M2A3 chassis, not necessary on IFV variant but for example AMPV or M109A7?

Oh yeah this is something I need to show, because US Army made a very smart moe recently. You see, when M113 will be withdrawn from service, US Army effectively will have only two families of vehicles in it's Armored Brigade Combat Teams.


This is the idea, over 75% of ABCT tracked vehicles fleet will be based on IFV components.


So medium tracked vehicles will be one family of : M2A3's, M7A3's, AMPV's, M109A7's and M992A3's.


Heavy tracked vehicles will be family of : M1A2's, M1150's, M104's and it seems US Army also want to proceed with ECP for M88A2's which means they might aim at providing components unification between M88A2's and M1 series.



As we can see AMPV will also provide complete replacement for M113's in form of more mobile, better protected, more survivable vehicle with greater capabilities.

The general purpose variant of AMPV actually give us some nice options as various weapon carrier options, it's chassis model can also serve as better platform for unmanned turret intended for IFV variant. In such case such modified M2A3 will be able to carry 3 crew members, and if I counted properly, there is 10 seats for dismounts inside.


So a SPAAG based on AMPV chassis becomes a viable option. Actually something like a hybrid gun/missile system would be great, comparable to Russian Tunguzka or Pantsir, eventually something like South Korean K30.


Actually K30 would be closest to such system, the one on the photo is early variant without missiles, but I wonder if US could not just puchase a license for turret and mount it on Bradley AMPV chassis, it could actually work as quiet fast and cheap solution for lack of AAD system for ABCT's.

Anyway this is how it looks like, and where I see opportunities for US Army to improve.

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15 hours ago, Invader ZIM said:

Didn't we have Bradley ADF vehicles in the past decade?  They were called Bradley Linebacker.





Great writeups and info by the way, I enjoy reading your articles Damian.


Yes, unfortunetaly M6 Linebacker was... well not really a great AAD vehicle, all were converted back to M2A2 or M2A3 standard. Which was a shortsighted decision, but let's be honest, a better SPAAG is needed, and it still can be baded on M2 chassis.


And thanks, I try my best to condensate some interesting informations in such short posts. :)

Another is the thing about M1's Auxiliary Power Units. There are several types. First was designed in the 80's and was in form of attachable module to the hull right rear sponson.



This type of APU did not served long, it was not the problem with APU itself, but the way it was installed, in rough terrain it can be lost and left behind.


So the next type of APU was installed in the turret bustle storage rack, and this is probably the most prominent APU type.



This type of APU is used in M1A1's and original M1A2's, it is good, it's working, however it is also exposed, which makes it vurnable to enemy fire and can cause fire hazard, which was experienced in Iraq.


Another type of APU was used in first production batches of M1A2SEPv1's.




However as far as I am aware, it didn't served long. It replaces rear left sponson fuel tank, however it seems there were some problems with it, and at some point both M1A2SEPv1's and M1A2SEPv2's got it replaced with additional battery pack, if I am not mistaken it's called Hawker Battery Pack or something like this.


It can be recognize that there is both no fuel tank in the left rear sponson, but neither there is exhaust port for APU.


In M1A2SEPv3 new more powerfull APU was installed in the same place, it can be recognized because of large exhaust port.


Another interesting feature that can be observed on M1A2SEPv2's and M1A2SEPv3's is the new rear camera for driver, this featue can be retroffited to all M1 variants, but I seen it only on variant mentioned.

Camera is hidden in the right rear light.


By the way I strongly recommend this walkaround of M1A2SEPv2 -> http://olivier.carneau.free.fr/photoengins/etats-unis/m1a2sep_v2_1/index.htm @dejawolfit might be usefull and interesting for you. ;) 

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Speaking about firepower of the M1.


We all know 120mm ammunition types from the past and presently used, APFSDS DU series M829, M829A1, M829A2 and M829A3, APFSDS WHA series KEW, KEW-A1 and KEW-A2, HEAT/MPAT series M830 and M830A1 as well as it's special HEOR variant M908, and of course Cannister M1028.


However right now all these will be replaced by two ammunition types only. Next generation APFSDS the M829A4 and new multipurpose programmable HE round AMP XM1069 (after standarization M1069).


Let's start with M829A4.




So what's so special? Well much is not known about the round itself, we know only it uses DU penetrator, entire round itself in size, weight etc. is similiar to M829A3. However notice in this PDF one thing, it have ammunition data link, one would ask, why APFSDS round need ammunition data link? HE ammo needs it for programmable fuze it can have, but a long rod? Now notice another thing, it is claimed that M829A4 can defeat 3rd generation heavy explosive reactive armor, and also active protection systems.


My friend have a theory that perhaps M829A4 is first programmable APFSDS round, with perhaps some sort of precursor, concept similiar to tandem HEAT warheads. And it kinda is confirmed by the new French APFSDS OFL 120 F1B NG.



Notice the cables groing from the round base somewhere to the upper parts of penetrator.


Curious isn't it?

Another type of ammunition is AMP - Advanced Multi Purpose XM1069 HE round with programmable fuze.



As we can see, this is very capable ammunition type, it have 3 modes of operation, standard detonate on impact, so works like normal HE, airburst which becomes more and more popular in tank ammo, and also delay/armor piercing mode.


And the last one is very interesting as it seems XM1069 is capable to pierce through T-55 class tank side turret armor, which is around ~150mm thick cast homogeneus armor, now imagine what XM1069 in delay/armor piercing mode will do with BMP class vehicle, first going through it's armor and then exploding inside.


These types of new ammunition can be fired with their full potential both from modified M256 guns that received ammunition data links (also FCS requires modifications), and also XM360 and XM360E1 guns that are from the start equipped with ammunition data links.



Another type of ammunition that was however fallen in to development limbo unfortunetaly, was XM1111 MRM (Mid Range Munitions), there were two types, KE with kinetic energy penetrator and CE with shaped charge warhead.




The thing is, that it actually worked, and this type of gun launched ATGM was really unique in it's range, it's maximum range was 12000m, compared to 5000m of Soviet/Russian/Ukrainian gun launched ATGM's.


Ok enough for now. ;)

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I thought the top attack STAFF round was really interesting and highly useful from a tactical perspective. I remember this on a thread here long ago and one poster claiming it didn't do anything TOw-2B didn't, but it has far more margin for error than a TOW-2B as it searches a swathe and can be fired higher vs the potential target to clear terrain - so you could lob one over a berm or tree line at a vehicle or concentration thereof which you can't do with TOW. It can also hit targets tucked close behind terrain which you can't do with the (still potentially very capable) newer guided rounds. However, it's cancelled in 2001. I'm sure we'll see something similar in future, albeit probably fielded by a potential adversary.



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16 minutes ago, ChrisWerb said:

I thought the top attack STAFF round was really interesting and highly useful from a tactical perspective. I remember this on a thread here long ago and one poster claiming it didn't do anything TOw-2B didn't, but it has far more margin for error than a TOW-2B as it searches a swathe and can be fired higher vs the potential target to clear terrain - so you could lob one over a berm or tree line at a vehicle or concentration thereof which you can't do with TOW. It can also hit targets tucked close behind terrain which you can't do with the (still potentially very capable) newer guided rounds. However, it's cancelled in 2001. I'm sure we'll see something similar in future, albeit probably fielded by a potential adversary.




AFAIK South Koreans are working on something similiar for their K2 tank.


However indeed the XM943 STAFF was interesting type of ammunition, and possibly very deadly one, especially for T tanks and their ammo storage.

The problem I see in the US, and other NATO member states, is that because they are democracies, and a lot of military development is under control of bureaucrats, plenty of good ideas got cancelled because they don't work well at the beggining of their development path, and need more refining, which means more time and money needed, and a lot of this intelectual potential is wasted because of short sighted, many times simply dumb, bureaucrats and politicians. But this is off topic right now so we should return to the original subject. ;)

Ok I am thinking about moving away from M1 right now, and perhaps going back to it later, so I am wondering about what next to write? Perhaps the M60 series? Or something else?

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At the time it was cancelled the US was of the opinion that Russia was a partner for peace and there were no other obvious potential conventional opponents that the US couldn't walk straight over with its existing conventional arsenal. You couldn't use STAFF, ATACMS Block II (BAT) or the Hornet Wide Area Mine in counterinsurgency conflicts, so they went away.


By the way Damian, I enjoy your armour posts on here and over on tank-net.com that I really look forward to reading them. Keep em' coming! :)

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By the way Damian, I enjoy your armour posts on here and over on tank-net.com that I really look forward to reading them. Keep em' coming! :)


Thanks, knowing that people enjoy my posts, really motivates. :)

Ok so maybe right now a less known fact about the M60 series, and to be more precise the XM60 development program. Well it's a very unknown fact that XM60/M60 was intended to be the first ever, mass produced tank, with composite armor. The armor itself was called Siliceous Cored Armor or SCA for short.


There were two variants of that armor, one integral intended for XM60 and second in form of addon armor modules intended as upgrade for M48 series.



Unfortunetaly due to many problems, development in the end was abandoned for XM60, and it was decided it will use conventional, cast homogeneus steel armor.

However it was not the first attempt of US to develop a special armor for tanks, in fact first development started even earlier during WWII in cooperation with UK. If not lack of imagination and shortsighted views of decision makers, perhaps the first tank ever, that was mass produced, and would use not only composite armor, but a modular composite armor would be... M4 series of medium tanks.


The most successfull and actually working composite armor for these tanks was the one codenamed HCR2 (Hollow Charge Resisting).





Test bed for this armor was M4A3 with HVSS suspension system, and older turret armed with 75mm M3 gun.


As mentioned above the armor worked against shaped charges, especially the ones from Panzerfausts, however was never adopted.


From what it was made? It was actually rather primitive armor made from aluminium boxes (25,4mm thickness) which were full gravel quartz and mastic substance (254mm thickness). It should provide protection against Panzerfaust 100 and Panzerschreck. This kind of armor did not provided however any significant improvement against conventional kinetic energy projectiles fired from tank guns and anti tank guns. However M4, contrary to popular opinions, have it's frontal armor absolutely adequate for this class of vehicle, as it's effective thickness was around 90mm, which means front hull and turret armor was only 10mm thinner than front hull armor of PzKpfw. VI Ausf. H1/E Tiger. Although history of WWII designs is something completely else, and should deserve separate posts.


When it comes to M60 series, these in general were well protected tanks for it's generation.


Upper Glacis:
M60: 93 mm at 65°
220 mm LoS
M60A1: 109 mm at 65°
258 mm LoS
M60A2: same as M60A1
M60A3: same as M60A1
Turret Front:
M60: equals 180 mm
M60A1: equals 250 mm
M60A2: equals 290 mm
M60A3: same as M60A1

Turret sides:

M60: 76mm

M60A1: same as M60

M60A2: ?
M60A3: same as M60A1

Hull sides:

M60: 76mm over crew compartment

50mm over engine compartment.

M60A1: same as M60

M60A2: same as M60

M60A3: same as M60.


So it was fairly well protected tank, one of the best protected tanks in NATO arsenal of that time alongside Chieftain.


There were of course various program to improve M60A1/A3 survivability, one of these program were codenamed M60AX.



Another program was to equipp tanks with Explosive Reactive Armor, and here interesting storry. ERA program was initiated by the US Army for their M60A3 tanks, however at the time ERA kits were ready, US Army figured out they already have enough various M1 variants, that soon with production continued, they will be able to completely replace M60A3's in active service. However ERA kits were ready, so who got interested in them? Of course USMC, because USMC always have lower budget, they would receive their first M1A1HC tanks in 1990, thus decision was made, that as interim solution, their M60A1's will be equipped with ERA kits originally developed by the Army for M60A3's.


Performance of these ERA modules is not known, however it seems it was rather effective solution, perhaps comparable with Kontakt-1, and superior to Israeli Blazer. In many ways this ERA general design is very similiar to Polish ERAWA-1 and ERAWA-2, which is curious, I would really want to take a peak in to guts of that US ERA and see if they are comparable in internal design.


On the other hand, ERA cover due to M60A1/A3 design was full of gaps in provided protection.

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Another interesting development for M48 replacement (before XM60) was T95. In many ways it was revolutionary design for it's time.



Development was performed from 1955 to 1959, vehicle was tested with several different turrets, and with many different weapon systems, including 90mm smoothbore gun T208, tough there were many other armaments, may I quote:



The T95 and the T95E1 are equipped with a T208 90 mm smooth-bore gun. The T95 equipment was installed on a fixed mount and was stabilized in two axes. The T95E1 equipment was installed on a recoil mount, but lacked stabilization systems. All T95 models were equipped with T320 armor-piercing rounds, which had a tungsten core, a diameter of 40 mm, and a muzzle velocity of 1520 meters per second. These rounds could successfully penetrate a 127 mm armor plate when fired at a 60-degree angle from 2000 yards. A standard T95 was equipped with 50 rounds.

The T95E2 retained the armament of its predecessor, the M48A2. With a 90 mm gun, it could fire a 74 mm anti-armor shell at 915 meters per second for a range of 2000 yards. It was equipped with 64 rounds.

The T95E3 was armed with a T140 105 mm rifled gun. With a muzzle velocity of 1079 m/s, the armor piecing capability at 2000 yards is 122 mm at a 60-degree firing angle. Standard equipment was 64 rounds.

The T95E4 was planned to have a T210 105 mm smoothbore gun. In order to accommodate the extra length of the rounds (112 cm), the gun was moved forward, preventing stabilization. The muzzle velocity of the round was 1740 m/s, with an armor penetration of 152 mm at 60 degrees at 2000 yards Standard equipment was 40 rounds.

With the appearance of the T123 120 mm rifled gun, it was decided that it should be installed on two of the four planned T95E4s. This variant was designated T95E6. The T123 gun had a muzzle velocity of 1070 m/s and armor-piercing capability of 122 mm at 60 degrees, at a range of 2000 yards.

There were also various types of fire control systems tested.



The T95E2 and the T95E3 were equipped with a fire-control system, identical to the one used in the M48A2, with a stereoscopic rangefinder and a mechanical ballistics computer.


The T95 also had an FCS which had an OPTAR optic rangefinder, as well as an electronic ballistics computer. It also featured a periscopic sight from the T44 and a T50 ballistic computer.


The T95E1 used a simplified targeting system – a rangefinder and a ballistics computer were omitted.


As well as various powerpacks.



Under the original proposal, T95 and T96 tanks had to be equipped with an X-shaped 750 hp 12-cylinder diesel engine. However, because this engine was only in the early stages of development, it was decided to temporarily equip the tanks with a 4-stroke, 8-cylinder AOI-1195 gasoline engine. The engine was placed transversely and was connected with the XTG-410 four-speed transmission. Three fuel tanks, with a total capacity of 780 liters, were installed in the engine compartment.


Despite higher fuel economy compared to the M48A2 engine, gasoline engines provided insufficient torque. At the same time, the development of the X-shaped diesel engine failed, so starting in mid-1958, other options were considered. As an interim measure, they decided to use a modified version of the civilian 12-cylinder, two-stroke, water-cooled, V-type, 570 hp GM 12V71T diesel engine.


A contract was signed with the Continental Motors Company in the development of the AVDS-1100 air-cooled diesel engine, and with Caterpillar to develop the LVDS-1100 water-cooled diesel engine. Both engines are quad-V-shaped, with an estimated 550 hp. However, tank testing with the three new power plants began after the retirement of the T95 program.


What is interesting, due to agreements, turret race ring of T95 and British Chieftain were the same, so turrets were completely interchangeable between both tanks.


When it comes to armor thickness, it's for vehicle on photo.



The majority of the hull is welded, but the front is a single massive casting. The upper part of the forward armor, or glacis, has a thickness of 95 mm and is at an angle of 65 degrees from vertical. The thickness of the roof and floor of the hull around the driver's compartment is 51 and 19 mm respectively; the thicknesses of said areas are 25 and 13 mm, respectively, around the fighting and engine compartments. The thickness of the main side plates vary from 102 mm up front down to 32 mm around the engine.


The cast turret has a ring diameter of 85 inches (the same as the M48). The frontal turret armor is 178 mm, and the sides are 78 mm. The shape of the turret is elongated compared to the M48. The gunner’s seat is situated to the right of the main gun in the front of the turret. The commander’s seat is also in the turret with a built-in 12.7 mm M2 machine gun, with an M28 periscopic sight for aiming. For 360-degree vision, 5 armored viewports are installed in the turret. Primary shells are stored in the lower section of the turret, beneath the ring.


What is also interesting, T95 was also designed with Siliceous Cored Armor (SCA) in mind.

In general it's one of the more interesting, yet least known US tank developments in history. However again, the concept was well too advanced for it's times, so in the end was cancelled. However, the T95E7 turret design was kept and work continued, thus M60A1 turret was designed, so in a way M60A1 and M60A3 have their lineage in T95 project.


A lot more can be found in Richard P. Hunnicutt books Patton - A History Of The American Main Battle Tank Vol.1 and Abrams - A History Of The American Main Battle Tank Vol.2.

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Ok some fresh news, it seems GDLS designed a completely new light/medium tank that will be presented 3-5 October at AUSA exhibition.


The vehicle is named Griffin, armed with 120mm smoothbore gun and uses technology from the M1 tank.





Demonstrating a New Series of Firepower: Land Systems’ lethal, medium-weight tracked vehicle demonstrator, the Griffin, combines the DNA of the Abrams turret and 120mm gun with innovations from the company’s full series of ground combat vehicles. 


This is extremely interesting news, seems like "squirrels" were right, GDLS have lots of aces hidden here and there. ;)

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Ok, so maybe about the development of M2 Infantry Fighting Vehicle now. I know that "Pentagon Wars" is very popular "source" of information in this subject but it's... false, very false I would even dare to say it's a lie made on purpose.


Well, maybe let's just quote mr. Hunnicutt here about the begginings.



In August 1963, the United States and the Federal Republic of Germany signed an agreement to develop a new main battle tank for use by both nations. Referred to as the MBT70, its high performance was expected to far exceed that of the M113 armored personnel carrier. 

The 1963 publication "A Study of Alternatives for a Post 1965 Infantry Combat Vehicle" envisioned a new high performance mechanized infantry combat vehicle (MICV) that could operate with the new main battle tank. Dubbed the MICV-70, it was not expected to be available before the end of the decade, in the meantime, the Combat Developments Command submitted a requirement for an interim MICV to be built prior to the availability of the MICV-70. This was approved in March 1964 and in June, a contract was awarded to the Pacific Car and Foundry Company for the design and fabrication of a prototype and five pilots of the mechanized infantry combat vehicle XM701. It also was referred to as the MICV-65. 


Using many components from the M107/M110 self-propelled artillery vehicles then in production, Pacific Car and Foundry was able to deliver the prototype in May 1965 followed shortly by the pilot vehicles. The prototype, registration number 12FP14, differed in some respects from the five pilot vehicles, registration numbers 12FP15 through 12FP19. Obvious recognition differences included the steps near the front of the left side armor and the location of the headlights at the extreme edge of the vehicle front. The first three pilots (P1 through P3) had steel hulls while P4 and P5 had aluminum alloy hulls. The turret was steel armor for all five vehicles. 


This hydraulically operated two man turret was armed with a 20mm M139 gun and a 7.62mm M73 coaxial machine gun. Other armament included two 7.62mm M60 machine guns and five 7.62mm M14 rifles at seven firing stations in the squad compartment. Two firing stations were located on each side, one in each rear corner, and one in the rear ramp. Vision blocks were mounted above the side and corner firing stations and an M27 periscope was installed in the hull roof above the ramp firing station.


Pilots P1 and P4 had ball mounts for the rifles and the remainder had firing ports. The M60 machine guns had ball mounts on all of the pilots. The 12 man crew consisted of the commander and the gunner in the turret, the driver, and nine infantrymen. The driver had one M27 and four M17 periscopes around his hatch and his hatch cover was fitted for the installation of an M24 infrared periscope. In addition to the door in the rear ramp, hatches were provided for the driver and on top of the turret and the squad compartment. The commander had a 360 degree view through eight vision blocks in the turret and the gunner was equipped with an M34C periscope. Combat loaded, the steel hull version had a weight of 54,050 pounds and the aluminum hull vehicle weighed 50,750 pounds. 


The XM701 was powered by an 8V71T diesel engine with an Allison XTG-411-2A transmission. The turbocharged engine developed 425 gross horsepower at 2,300 rpm. When the vehicle was afloat, the engine compartment was completely sealed and water from the outside was used to cool the engine. The flat track torsion bar suspension had five dual road wheels per side. The rear road wheel served as an adjustable trailing idler to maintain track tension. The 15 inch wide, double pin, tracks were driven by the sprockets at the front of the vehicle. The XM701 was fitted with the E51 NBC gas particulate filter unit. This was a modification of the collective protector designed for the MBT70. 


The unit pressurized the entire vehicle so that the crew did not need to wear individual masks. An auxiliary power unit was installed in the engine compartment for starting the engine in cold weather and charging the batteries during radio watches. Because the XM701 was expected to operate for 24 hours in the buttoned-up condition, a stove and toilet were included. Although weight and space restrictions eliminated the installation of a winch, two capstans were provided for attachment to the drive sprockets. When not in use, they were stowed on the rear of the vehicle to the left of the ramp. Two 150 foot lengths of nylon line were carried in the squad compartment for use with the capstans.

The vehicle had a maximum speed of 40 miles per hour on roads and 3.8 miles per hour in water. When afloat, the freeboard varied from about 6 inches for the steel hull vehicles to approximately 10 inches for the aluminum hull version. The cruising range on roads was
about 3 50 miles.


Ok so this is where it beggins, the XM701.




This vehicle never went in to production, and was considered more as a sort of interim test bed for new ideas that were later used in further development story of MICV program.


The actuall prototype was designated XM723.




As we can see the vehicle more closely reassembled to what would become M2.



Pacific Car and Foundry Company, Chrysler Corporation, and FMC responded with proposals. The FMC concept was accepted and they were awarded a contract in late 1972 to construct three prototypes, a ballistic vehicle, and 12 pilots.


The first prototype was delivered in 1974 and allthree were completed by the Summer of 1975. In many ways, they resembled the FMC AIFV, although they were larger and heavier. The Cummins VTA903 diesel engine was installed in the right front hull. Developing 450 gross horsepower at 2,600 rpm, it was coupled to a General Electric HMPT-500 hydromechanical transmission. The front mounted final drives and sprockets drove the 21 inch wide, single pin, tracks. A torsion tube-over-bar suspension supported the vehicle on six dual road wheels per side with return rollers.


The XM723 was assembled using 5083 aluminum alloy armor except for the sloped sides. These were 7039 aluminum alloy armor. Spaced laminate steel armor was added to the vertical sides and rear. Frontal protection was enhanced by a the trim vane. At least two different high displacement trim vanes were installed on the prototypes. The crew arrangement was similar to that in the AIFV with the driver in the left front hull and the commander immediately behind him. The driver was provided with four periscopes and the commander with five periscopes in the hull roof around their hatches. The gunner was in the turret just behind the power plant compartment. He had six periscopes around his hatch and an M36E2 periscopic sight. Eight infantry soldiers were seated in the squad compartment. 


Six firing ports and periscopes were located two on each side and two in the rear ramp. Six .45 caliber M3A1 submachine guns were carried for use as firing port weapons. The turret armament varied during the test program. Although the 25mm Bushmaster was specified as the main armament, it was not yet available. The 20mm gun M139 and the 20mm gun XM236 were installed at different times. In a similar manner, the 7.62mm M219 coaxial machine gun was replaced by the 7.62mm XM238 machine gun. The latter was a modified version of the 7.62mm M60 machine gun.


Combat loaded, the XM723 weighed about 43,000 pounds. Its maximum road speed was 45 miles per hour and it could swim, propelled by track action, at about 5
miles per hour. The cruising range on roads was approximately 300 miles. The tests of the XM723 continued into 1976. Although there were some problems with the new transmission and suspension system, they were resolved after a few months delay in the program. However, the greatest concern was the high cost of the new vehicle compared to the familiar M113 series.


Ok folks, that's enough for now.

Edited by Damian90
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I love the "Pentagon Wars" movie (particularly because it has the Dread Pirate Roberts in it), but it's important to realize that it was written as a comedy, for maximum comedic effect. And while Kelsey Grammar is made to be the villain in the film, I see a lot of reason in the arguments he's offering in the Senate hearings. He tries to get a project finished where too many conflicting design requirements are threatening to derail everything, and in addition he's got to deal with an airforce captain who think that he's on to something big.


Even in the film you can see two sides of the coin, if you're willing to pay attention and listed to the arguments brought forward. And hey, it's fun to watch.

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6 minutes ago, Ssnake said:

I love the "Pentagon Wars" movie (particularly because it has the Dread Pirate Roberts in it), but it's important to realize that it was written as a comedy, for maximum comedic effect. And while Kelsey Grammar is made to be the villain in the film, I see a lot of reason in the arguments he's offering in the Senate hearings. He tries to get a project finished where too many conflicting design requirements are threatening to derail everything, and in addition he's got to deal with an airforce captain who think that he's on to something big.


Even in the film you can see two sides of the coin, if you're willing to pay attention and listed to the arguments brought forward. And hey, it's fun to watch.


I think I preffer the books. Truth to be told I never liked movies too much, especially ones trying to "speak" about such difficult issues like engineering.

And in the end, IFV is a result of conflicting requirements. As well as in the end M2 proved to be a good design.


The problem I see is that, movie makers are, and let's be honest here, when it comes to weapons, and how they work... they are morons more or less. And I think we can all agree on this.

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