Smoothbore gun accuracy

[jazjar]

Why are the German and American smoothbore 120mm guns not as accurate as stated? For example, the round often goes outside of the circles in the Leo and M1's gunsights. ( The small center one in the Leo 2 and the circle/box in the M1). At ranges of 1500m+ this often leads to multiple misses, the famed "First round hits" are almost non existent at these ranges. I won't even mention other sources that state that m256s and L44/55s can score at 4000+ , because I know Ssnake will find a way to falsify them. I am just wondering if Steelbeasts is accurate or not.

[sabot_ready]

Could you please post your sources. Even if Ssnake would falsify them, I would like to see them.

[Ssnake]

SB Pro applies a random error to each round - laterally, in elevation, and in muzzle velocity. All of them are of the Gaussian (normal distribution) type. The lateral and elevation error is, where possible, based on manufacturer claims for each ammunition, or on data from firing tables, or, if neither can be found, it is approximated by using similar values from comparable ammunition types where the data are known.

Where the data are known, there is a systematic error in our shot simulation of, I think 0.001 mil for some coding reason that I don't understand, but since even the standarddeviation ("S") for shot to shot variation usually is in the .20 to .50 mil range for medium and large caliber ammunition, I'm not losing sleep over it.

(We're limiting the deviations to 3S, which would cover 95% of all rounds in reality; that means that for an SD of .25mil only about 68% of all rounds will be in a circle of .5mil diameter, and all rounds in a circle of three mil diameter (!))

It has very little to do with the type of gun, actually. Muzzle velocity variations are caused by variations in the propellant temperature, the amount of propellant, manufacturing tolerances in the projectile (size, material composition), temperature-dependent variations of barrel and projectile diameter, and of course barrel wear. Elevation and azimutal error stem from deviations of the barrel geometry from the theoretical ideal of a perfect cylinder, positioning errors of the stabilization system, clearance/tolerances in the mechanical fitting of gun tube in cradle, cradle in mantlet, and mantlet in turret, ...

In summary, our rounds show pretty much exactly the kind of behavior that they do in real life as well, and they will behave just the same irrespective of the gun tube technology. The "higher accuracy" of rifled gun tubes has an effect on the exterior ballistics; the described reasons for shot deviations all fall into the domain of interior ballistics.

Where we do deviate from reality is that occasionally some rounds have a lateral standarddeviation that differs from the vertical. Usually these differences are small (in the order of magnitude of .02 mil), and we then took the liberty to use the arithmetic average in these cases. The one vehicle where this is a rather bad approximation is the GROM gun of the BMP-1 since it is especially sensitive to crosswind but doesn't have such a bad dispersion in elevation. I still hope that one day we can address this.

[jazjar]

Those sources were from a long time ago, but I'll try to dig some things up. The first one I remember from memory, it was a little spacey and unspecific, but I guess the important part was that it is in the Steelbeasts manual, written by Ssnake himself. He stated on P.61, the "Laser rangefinder system" section, that "A lot of information is inputted into the computer to ensure a first round hit." (Ensure, people, ensure!) I know this is a little fuzzy, but still, it came from Ssnake's pen! 2. "The M1A2 Abrams tank has a two-axis Raytheon gunner's primary sight - line of sight (GPS-LOS) which increases the first round hit probability by providing faster target acquisition and improved gun pointing" From Army-Technology.org. Now I know that we're talking about the M1a1 here, but the Leopard's sights are still stabilized in two axes, correct? And they have the dispersion problem as well. That's all I can remember from now.

[jazjar]

So, going back to Ssnake, you're saying that what happens in SB also happens in real life as well ( talking about dispersion )?

[Ssnake]

Like I wrote, the shot deviation is realistic and intentional. No gunner, no matter how good, can avoid these random variations. It has nothing to do with skill, and everything with manufacturing tolerances and thermic expansion and contraction behavior of the materials used that simply cannot be avoided with today's technology (or ever, IMO, as long as we will continue to use the technology of accelerating projectiles in cylindrical contraptions to lob them over a distance - irrespective of the way how this acceleration will be applied (chemical, electro-chemical, electro-thermal, or purely electrical (be it the Gauss gun or the Rail gun principle)).

[Grenny]

Why are the German and American smoothbore 120mm guns not as accurate as stated? For example, the round often goes outside of the circles in the Leo and M1's gunsights. ( The small center one in the Leo 2 and the circle/box in the M1). At ranges of 1500m+ this often leads to multiple misses, the famed "First round hits" are almost non existent at these ranges. I won't even mention other sources that state that m256s and L44/55s can score at 4000+ , because I know Ssnake will find a way to falsify them. I am just wondering if Steelbeasts is accurate or not.

Do I understand this correctly: You don't score 1st round hits as expected in SB over 1500m?

Movers or stationary? You shoot or the AI?

Offen there is a problem in the FCS, located in the space of 0.5cm to 35cm in front of the GPS ;-) ...in short: aiming errors.

You got to keep in mind:

Did I lase the target correctly?

Is the aiming point on center mass?

Can't speak from own RL experice on 120m here (biggest gun I fired had 25mm...thanx to the US forces in germany for that :-P ), but i sometimes think SB "is to good to us" in the way of ammo dispersion as there are f.e. no crosswinds! In my current job in the reserves (G4) I get to see the calibration results of our tanks for a given range (far below 4000+). Belive me, dispersion there grants many hits...but NOT 100%

Remeber when they give a "maximum effective range" on a weapon, it means you are MORE likely to hit then to miss at that range 8-) F.e. 50,1% chance for a hit is more then 49,9%

In SB, if you follow the laser rules, you can be pretty shure to hit the target.

[rump]

At ranges of 1500m+ this often leads to multiple misses, the famed "First round hits" are almost non existent at these ranges.

The maximum range on the SB Tank range is about 2400 meters. I, and many others, score first round hits al the time at this range, even with HE on a moving target.

- Rump

[IrishHussar]

There are many reasons for a first round miss including minor variations between rounds imparted at manufacture.

Perhaps 12Alpha could list all 10 for us LOL

Irish

[MAJ_Fubar]

I can back up Ssnake on this one. After all, an M1A1/A2 is considered screened if it can place one sabot and one HEAT in a 1.75m panel @ 1500m, irrespective the fall of individual shots . In my experience, when determining a discrete Computer Correction Factor for a given tank the shot group dispersion almost always falls within a .20 to .30mil range unless there is something mechanically wrong with the tank...or the crew is completely FUBARed.

[Hunt3r]

Usually the only time where I really will just flat out miss or something similar is at the very edge of engagement distances, 4000 meters or so. I'm not a very good gunner, either.

[Tacbat]

So, going back to Ssnake, you're saying that what happens in SB also happens in real life as well ( talking about dispersion )?

Do you own a firearm?

[Sean]

If reliable hits at 1500M+ are not possible in steel beasts, then the human crew needs some more training/practice :-)

[SeanPatrick]

...i sometimes think SB "is to good to us" in the way of ammo dispersion...

In SB, if you follow the laser rules, you can be pretty shure to hit the target.

I agree. I've made shots which I thought I lased in a sloppy manner and they were right on target. I think the key is understanding first/last return and where to put the reticle when lasing, which may not be the same as when firing.

[jazjar]

You people must be playing the old version, LOL. Play the Multiple units tutorial for all of the smoothbores. Play as the CO tank. You will find that many rounds will fall short or over the target, and many will fall left and right. ( just slightly, barely outside the circle ). This is what I am talking about.

[12Alfa]

There are many reasons for a first round miss including minor variations between rounds imparted at manufacture.

Perhaps 12Alpha could list all 10 for us LOL

Irish

Hey how did I get involved in this??:eek2:

I would have to did up my gunnery manual to give you the 10 reasons, but I think we have posted them here on the forum.:cul:

It's been over 15 years for me teaching gunnery.:frown:

[Volcano]

You people must be playing the old version, LOL. Play the Multiple units tutorial for all of the smoothbores. Play as the CO tank. You will find that many rounds will fall short or over the target, and many will fall left and right. ( just slightly, barely outside the circle ). This is what I am talking about.

...or perhaps you are not getting good lases on the target? With respects, it is generally a bad idea to newly show up and tell people who, for the most part at least, have been playing SB for over 10 years, and tell them that the reason they don't agree with you is because they are playing some old version of SB.

Anyway, the proper answer to your own question is that rather than discussing generalities and assumptions go forth and find dispersion data for smoothbore munition rounds that dispute the current behavior.

All I can say is, in real life when you screen a tank before you go on the tank range you fire at "the octagon" screening panel after boresighting. The octagon is 1.75 meters (5.74 feet) in diameter and the panel is 1200 meters (105mm M1) and 1500 meters (M1A1 / M1A2) distant (source: FM 17-12). The octagon allows for the standard dispersion of rounds fired from a three round shot group. If all three rounds are in the octagon, then you are considered to have a good boresight and are "screened" and ready to negotiate the range -- no one bothers to worry their head why one round is at the top of the octagon the other round is at the bottom 1.75m apart -- you are "on target" as far as the ballistic gods are concerned.

So what does this mean? Well, the 1.75m diameter octagon is allowing for a tolerance of dispersion at 1500m. On some tanks I have placed three rounds one inside the other's hole and on some tanks they were scattered within the octagon. I am sure it has a lot to do with the varying amounts of gun tube wear and when the tube was replaced last (something like 3,000 rounds required a replacement if I recall correctly -- straight outta' memory though!). So yes, perhaps a brand new smoothbore tube would have noticeably less dispersion than one that has fired a couple of thousand rounds in its lifetime, but of course SB must model an average dispersion.

A similar principle is true when you try to zero a rifle. You may have the rifle fully stabilized on a mount and fire at the same point three times, but the bullets go where they want at 25m zero target -- it is not a laser beam. You then take the average of the shot group from its natural dispersion and walk on your sights, zeroed. This is how it works on the tank except you are doing it the other way around (to save on ammo costs). Speaking of zeroing, naturally a rifled musket versus a smoothbore musket would have less dispersion.

Edited August 25, 2011 by Volcano
typo

[sabot_ready]

Just to clarify something. you said

For example, the round often goes outside of the circles in the Leo and M1's gunsights. ( The small center one in the Leo 2 and the circle/box in the M1).

Do you mean where the round lands or that during flight it leaves the circle?

I ran a test where I engaged T72's at different ranges with A3 ammo in a M1a1 At the following ranges I report the number of hits out of 40 shots.

1000M -38 hits in 40 shots. The 2 misses went thru the area where the turret would have been since it cooked off.

1500M -37 hits in 40 shots. The only change in the misses was I placed 2 rounds under the tank thru the tracks

2000M -36 hits in 40 shots. Again the misses were due to the turret missing.

3000M- 34 hits out of 40

All rounds landed in the center square. The only thing that changed was the size of my target.

There does seem to be a bug where the rounds pass thru the target and the TC will report them short or over. You can see the flash of the hit but also the ground gets kicked up. Its like he is only seeing the final splash.

Edited August 25, 2011 by sabot_ready

[Grenny]

You people must be playing the old version, LOL. Play the Multiple units tutorial for all of the smoothbores. Play as the CO tank. You will find that many rounds will fall short or over the target, and many will fall left and right. ( just slightly, barely outside the circle ). This is what I am talking about.

Just to be shure: that are your rounds...or the one fired by the AI?

The AI is as good as "you made them"...if you missed 6 out of ten time on the tank range, they are likely to just as good.

If you have these results by "manually" firing, I suggest for some probs in the fire procedure.

What time zone are you in? Can you join MP sessions? We could go "at the range" and figure it out.

[Ssnake]

All I can say is, in real life when you screen a tank before you go on the tank range you fire at "the octagon" screening panel after boresighting. The octagon is 1.75 meters (5.74 feet) in diameter and the panel is ... 1500 meters (M1A1 / M1A2) distant

In other words, the target is 1.16 mil in diameter, or covers a circle with radius

0.583 mil. Divide by three (0.194 mil) and you are closer to three standarddeviations of the proposed natural shot dispersion with an SD of 0.2mil. Three SD will be good for about 99,7% or all rounds. That means that the chance of a properly boresighted tank to miss one of the three rounds on target is less than 1%.

[Captain_Colossus]

Where we do deviate from reality is that occasionally some rounds have a lateral standarddeviation that differs from the vertical. Usually these differences are small (in the order of magnitude of .02 mil), and we then took the liberty to use the arithmetic average in these cases. The one vehicle where this is a rather bad approximation is the GROM gun of the BMP-1 since it is especially sensitive to crosswind but doesn't have such a bad dispersion in elevation. I still hope that one day we can address this.

Less the problem of the gun as it is the shape of the projectile, is it not? That's true of man portable RPG-7 rockets. The operation is counter-intuitive as the operator doesn't fire into a crosswind to compensate, but with it; the influence of a crosswind from left to right for example exerts greater force on the fins/booster portion than the warhead, causing the rocket to turn into the wind and veer off left. To compensate, the RPG gunner aims to the right with the wind.

[Ssnake]

Less the problem of the gun as it is the shape of the projectile, is it not?

True in real life, but from a procedural perspective (=SB Pro's approach) that's a moot point. In the end, what you see as the gunner is that the round isn't flying where you aimed it, and you could care less WHY that is so. What counts is that you know what to do about it (nothing, if it is natural shot dispersion - or to correct your aim if it is a systematic error from exterior ballistic factors, or bad aiming. The art is to know which is which. ).

Of course, the "Buck Rogers" GROM gun and its PG9 projectiles area very special case. Who knows, one day we may actually have a BMP-1 gunner's position.

[Captain_Colossus]

Right. I mean to explain the why rather than just that the deviation occurs, or in other words what justifies adding a random deviation spread in the simulation model in case anyone did not know what this behavior correlates with.

[jazjar]

Volcano I think you did the best job of explaining the real life gun performance to us. Bravo, anyways, A smoothbore gun in Steelbeasts, or al least my copy could not acheive this. My gunnery skills are good. I always have a still reticle when I fire, and dump lead on stationary targets in the Abrams. Still, the important thing is, my smoothbores can barely hit inside of 3.5 meters ( t-72) at 1500 meters. My tank would fail the octagon test big time. I will try to get a target with the octagon dimensions and perform some tests with that.

[Tacbat]

How about posting a vid on Youtube so we can see what's going on?