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Marder gunnery effectiveness.


ChrisWerb
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2 hours ago, ChrisWerb said:

Mercuric compounds are usually found in the primers on older small arms amunition. They are what makes the ammunition corrosive, requiring extra thorough cleaning (or just cleaning).

 

Mercury fulminate primers were/are non corrosive.  They were known to weaken over time, giving ammunition a shelf life, and leading to lots of hangfires/misfires with ammunition.  So chlorate primers came along, to make sure that you'd get a bang when you pulled the trigger instead of a click.

 

Potassium chlorate or sodium petrochlorate are the corrosive primers, which were also a replacement for the mercury fulminate primers.  When you burn those they make potassium chloride or sodium chloride, which gets carried by the propellant gasses all through the weapon.  In the event of a primer puncture then it blasts back into the action too.  These are still made and used, for various reasons.  They can work reliably after over 70 years in storage.  I have some 1939 dated 8x57mm Mauser ammunition that still works great.  There is also 2016 dated Ukrainian made 7.62x39mm "military surplus" (Probably more like "we need money") ammunition being imported into the US right now, made with corrosive primers, so they're still in use over there for whatever reason.

 

Lead styphnate and lead azide came into use after WW2 as a non-corrosive priming mixture.  I understand that some of the early mixtures didn't work well in cold weather, but that seems to have been ironed out pretty well by now.

 

As for cleaning, it's more than just simple cleaning.  You need to use specific chemicals which tend to be nasty and toxic (like nitrobenzene), or water based cleaning compounds, to get the salts out.  Oils, most solvents, CLP, etc won't do it.

 

Of course, cleaning small arms is one thing...I've got no idea what kind of primers are used on things like 20/25/30/35/40mm autocannon rounds, let alone 100/105/115/120/125mm main gun rounds.  However, this touches upon another subject...It's one thing to take apart a rifle or a belt fed machine gun to clean it, but a totally different thing to have to clean your tank's main gun...And that's something we don't really hear about much, probably because cleaning the gun is not a glorious part of crewing a tank.  But it's still important.

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Hans, I'm not a chemist (most of my weapon cleaning problems involved copper, not mercury!), and I'm sure you're right (particulary about the potassium chlorate or sodium petrochlorate part), but you might want to take a look at this forensic treatise. 

 

Cover.

 

Excerpt.

 

Table.

 

Whole book (with elements redacted).

 

 

 

 

Edited by ChrisWerb
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8 hours ago, Maj.Hans said:

It's one thing to take apart a rifle or a belt fed machine gun to clean it, but a totally different thing to have to clean your tank's main gun...

 

Well... it's more demanding physically, but a much, much easier procedure actually. You have the copper brush and the 5m rod, you put some oil on the brush, and have a go at it. The old in-and-out game with three guys thrusting and pulling, and the fourth at the breech. When done, two or three more times to dry up the mess, and that's it.

Don't forget, a rifle barrel is designed for a lifetime of what, 10,000 rounds? 50,000?

The 120mm L44 is already a "long life" design, with a warranty to cover 1,500 rounds (rumor has it that it might last much longer). 105mm L7 gun has a designed lifetime of what, 800 rounds?

 

So, I suppose that means that the requirement to keep the gun "squeaky clean" is actually less of an issue with bigger calibers, simply because they are meant to only last for much, much fewer firing cycles.

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My memory could be failing, but I think I read a few years back that the British Army (and I believe the Bundeswehr) now use automated/power assisted barrel cleaning systems. There are a number of automatic and power assisted systems out there for both rifled and smooth bore guns, for example:

 

http://www.nides.cz/fileadmin/slozka/pdf/Airnesco_Military_Barrel_Cleaning_System.pdf

 

http://www.burevestnik.com/products_engl/1i39.html

 

http://www.weaponproducts.com/bore-cleaning-system/

 

http://www.vapprocorrosioncontrol.com.au/abc-tank-barrel-cleaning-system.html

 

There are quite a few more out there - I have no idea which, if any, have been adopted and by whom.

 

 

Edited by ChrisWerb
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21 minutes ago, GSprocket said:

Life depends on ammunition. ISTR that Bumar indicated EFC values for M829A2/DM53 as 5.0 and M829A3 as 6.0, with DM12/M830 as EFC 1.0...

Which with a 2:1 mix of APFSDS/HEAT suggests a life of around 380 war rounds.

 

I would guess that, historically, few tanks get to fire 380 war rounds in actual conflicts either because the conflict was not that intense or because they got knocked out or were returned to depot for maintenance or replaced and relegated to training duties etc..

 

I would also guess that practice ammunition causes significantly less wear due  to reduced pressures/velocities.

 

Late edit: If you think in terms of "stowed kills" you could knock out our entire remaining fleet of Challenger 2 tanks (many of which have already been torched) without wearing your barrel out.

Edited by ChrisWerb
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11 hours ago, Ssnake said:

 

Well... it's more demanding physically, but a much, much easier procedure actually. You have the copper brush and the 5m rod, you put some oil on the brush, and have a go at it. The old in-and-out game with three guys thrusting and pulling, and the fourth at the breech. When done, two or three more times to dry up the mess, and that's it.

Don't forget, a rifle barrel is designed for a lifetime of what, 10,000 rounds? 50,000?

The 120mm L44 is already a "long life" design, with a warranty to cover 1,500 rounds (rumor has it that it might last much longer). 105mm L7 gun has a designed lifetime of what, 800 rounds?

 

So, I suppose that means that the requirement to keep the gun "squeaky clean" is actually less of an issue with bigger calibers, simply because they are meant to only last for much, much fewer firing cycles.

 

I was thinking more in terms of the action parts and not just the barrel.

 

What do you do if your L44 has a sticky breech that just won't shut reliably?  On one of my AR-15s or my HK-33 I can just pull it apart in my lap and clean it.

An L-44 breech assembly seems like the kind of thing likely to sever fingers and/or toes if handled incorrectly...

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11 hours ago, ChrisWerb said:

Hans, I'm not a chemist (most of my weapon cleaning problems involved copper, not mercury!), and I'm sure you're right (particulary about the potassium chlorate or sodium petrochlorate part), but you might want to take a look at this forensic treatise. 

 

Cover.

 

Excerpt.

 

Table.

 

Whole book (with elements redacted).

 

 

 

 

What's interesting is that they seem to be categorizing the primers as "mercury containing" rather than mercury fulminate based.  From what I recall, you'll find both lead and mercury in all different kinds of primers, including chlorate primers.

 

They tend to be rich in toxic heavy metals in general, with "Sintox" primers (I think that's actually a registered trademark to a Euro based company) being a big deal.  For those who shoot in indoor ranges you get exposed to all kind of nasties.

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56 minutes ago, Maj.Hans said:

What do you do if your L44 has a sticky breech that just won't shut reliably?  On one of my AR-15s or my HK-33 I can just pull it apart in my lap and clean it.

An L-44 breech assembly seems like the kind of thing likely to sever fingers and/or toes if handled incorrectly...

 

Crews here are taught how to strip the breech and yes there are heavy pieces and some are under tension.

 

If its not something the crew can fix then you call the "gun plumbers".

 

For us that's RAEME, for the UK REME, unsure who the US / German maintenance guys are.

 

Yes its dangerous but that's why you are trained. For example, you push the round home with a closed fist so the closing breech pushes the Loader's hand out of the way (using an open hand can be bad). I know a couple of guys who have left finger tips on the wrong side of the breech.

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7 hours ago, Maj.Hans said:

What do you do if your L44 has a sticky breech that just won't shut reliably? 

An L-44 breech assembly seems like the kind of thing likely to sever fingers and/or toes if handled incorrectly...

 

Exactly. How sticky, do you think, does it have to get in order to "stop shutting reliably"? ;)

What do you think would happen if a 120mm gun breech didn't shut reliably?

 

Of course a tank will go, at some point, into level 2 and level 3 maintenance. Who knows what they are doing to the gun assembly there. On the crew level however this is absolutely no concern.

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8 hours ago, dpabrams said:

Marder gunnery? Where the hell is the manual? And for that matter the Luchs? I don't see Wiki entries and I cannot figure them out. Well I can a little but I the "Page

 Down" key is no good for selecting the rate of fire.

...+ you can not select a rate of fire. its full auto or single fire. Just check the Marder entry in the controls menue...this will explain a lot.

As for the wiki entry.. I'm on it...but have my hands full with RL stuff at the moment.

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Slightly off topic, but I started a thread about Warrior gunnery problems over on tank-net.com and it would appear the vehicle always had powered traverse, but not elevation. Wobbly Head (who, as you know, knows his stuff) says the accuracy problem was a manufacturing defect and was fixed.

 

http://www.tank-net.com/forums/index.php?showtopic=42050#entry1269820

 

I'm assuming there is no way to have a combination of power traverse and manual elevation in SB?

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