Small arms ballistic cross check

[firebugs]

Rats, if you wouldn't mind, could I get your actual values for ballistic coefficients for the following:

K98k

Mg34

Mas 36

Lebel (sniper)

Enfield

Boyes ATR

PZB 39

I'm doing some testing (again, commence headache ), and from what I can do, I'm getting;

k98- .21

Mg34- .30

Mas 36- .30

Lebel- .24

Enfield- .25

Boyes .95

PZB 39- 1.17

Also, I noticed that the Lebel and MAS have a listed MV of 716 m/s in the game. That is about right for the lebel, but the MAS is ~820m/s with 139gr light ball.

[GOPHUR]

The first two look pretty right on.

These take a long time to look up (multiple files are not great for research) and as I have no immediate benefit for that time spent and a big list of important things to do (sorry them's the breaks) I'll just leave it at that.

If you want to share some testing methodology that would lead to some benefit for spending the time to look all of information (that to my mind is vetted to 95% which is plenty accurate) I'm all ears.

[firebugs]

I shoot fru's at various ranges on the training server and it tells me the joule damage input, I take an average of 10 shots. I then plug in ballistic coefficients with the correct bullet weight and MV at www.jbmballistics.com until my test numbers match the ballistic program (most were able to match spot on at 3 or 4 different ranges.)

As an avid collector of wwii era firearms, reloader, and long range shooter I see lots of things that raise my eyebrows.

I just want to make sure my testing data is accurate vs the real numbers in the system before I base assumptions and opinions.

[jwilly]

I'd think that a ten shot average might not be a large enough statistical population to reliably reveal the mean of the shot variation code.

[delems]

Correct, need minimum of 30 samples.

[DOC]

standard we employ is 100 sample shots for every article of ordnance

that way when we average results for mean it represents a % we can rely on and compounds errors less rather than more

anything less than 100 sample size not interested

yes, I'm brutal about that

most (probably you too) expect a certain level of effort, and that's the minium here

[GOPHUR]

I still don't get what you are wanting to test? What is the goal of the testing? Do you want to audit joules delivery? Are you wanting to check trajectories?

I just don;t really see the point of the exercise other than grognarding it up , which hey, is a great pursuit in and of itself don't get me wrong. I've worked with several super ballistics geeks over the years who have been into that stuff. They wrote what we have and I don't see much point in revisiting it without a goal in mind.

[firebugs]

My testing to find the bc's really has no importance. I would like to know what they are because if any of the rifle/MG rounds that I tested are matches (the BC that I got matches what's in the game) there's a serious flaw.

This is where I get kicked in the nuts. I don't have any historical data to provide a correction. So I suppose its a fruitless endevor, but I can tell you that none of them should be below .35

The most glaring example to me that something is wonky is that the mg34 and k98 are different, though they shoot the same bullets (albeit at different velocities-- mg ammo is hotter loaded, the same bullets, so should be the same BC).

There aren't even bullets blunt enough on the market to maintain the same weight with such low BCs, and these are highly pointed spitzer bullets you're modeling. I understand this has a small place in the wwiiol world and level of importance, none the less, it is incorrect, and ill do what I can to research some info to provide a correction.

[firebugs]

Likewise, there's no way a 225 gr. 8mm (pzb 39) bullet is going to have a BC of over .7

1.17 is insane. Like a 350+gr hypodermic needle in that caliber.

.95 is also high for the .55 boyes. it's a 735 gr. flat-based projectile, for reference, the US military has done testing that says 750 grain .50 bmg AP bullets (mind you, they are narrower, have longer noses, and boat-tails-- all help increase BC) have a BC of only .67. I can attest to the accuracy of that BC, as I have shot several AP and API bullets from my .50 bmg to ranges well exceeding 1000yd.

Unfortunately I'm stationed 2000 miles away from home and don't have access to any references. I'll see what I can pull up on the internet or if there are any decent books locally.

EDIT: by the way, I hope your .30-06 M2 ball (M1, M1918, M1903 etc) BC is somewhere 'round .380. I'm fairly positive I can find that one online.

And about the sample size, not that it matters, but the majority of them were repeats. A typical 10 shot string would look like 417, 409, 417, 417, 417, 426, 417, 414, 417, 426 (Joules of course) etc... However, it got me close enough to be able to very accurately predict bullet drop and energy at various ranges. I was able to shoot a FRU and tell how far away it was, and predict energy extremely accurately (within 5-10J) on a known-distance FRU. I won't argue with your standards, just saying that what I did was close enough for me to know something's up. Perhaps this weekend I'll do full 100+ unit samples.

Edited June 9, 2011 by firebugs

[firebugs]

Did a couple 100-shot samples tonight for the K98k.

K98k- 198grain (12.8gram) bullet @ 745m/s

500m 100 round total energy- 55478 Joules

Average energy per shot- 554.78J

Resulting BC on www.jbmballistics.com- .2061

1000m 100 round total energy- 26361J

Average energy per shot- 263.61J

Resulting BC on www.jbmballistics.com- .2068

The difference between .2061 and .2068 is literally negligible for all practical purposes. Why it is different between the two is more than likely a round-off difference between JBM's calculator and WWIIOL's calculator, or some minor variable due to elevation or the like.

So what does that tell me? Well, over a year (or two?) ago, I was given the K98k's BC by GOPHUR (not sure if you remember or not), so the .21 I know is what is actually used in the game code. My testing produced something that is over 98% correct to what is in the game. My testing method, then is a fairly accurate way of judging ballistic coefficients used by the RATS. Granted, I've only done the 100 shot test on one rifle, but it matched extremely closely to my 10-shot test conducted earlier. The max spread of impact energy is less than 10J (at 1000m for example it was 260j to 267j max spread. Most were 263 or 264.).

Now, let's compare that .21 BC to a commercially available bullet similar in shape, diameter and weight to the old 198 grain s.S. Patrone bullet, the Sierra 8mm 200gr Matchking.

And if you look on Sierra's website for the ballistic coefficient of their bullet, you get this. Being that the MV of the K98k with s.S. patrone is well over 2300 fps, it's initial BC is .520.

Here's a couple charts showing the ballistic difference between a .2061 BC and a .520 BC. (the red highlight indicates at what point the round goes sub-sonic)

I'm not saying that the WWIIOL k98k's BC should be .520. I'm just saying that it should be a hell of a lot closer to .520 than to .21 or .2068 or even .30.

Think about it. Every single rifle, lmg, tank co-ax, wing-mounted MG, turret mounted MG, is performing WAY below what it should be on a "historically accurate" comparison. Rounds are taking longer than they should to get to target, dropping more than they should, and hitting with less energy than they should, across the board.

I should think now it's just a matter of research, trying to find out what the real-world bullets did.

EDIT: Not sure if you'll accept Wikipedia as a source or not.

http://en.wikipedia.org/wiki/8x57mm_IS

The German standard sS (schweres Spitzgeschoß—"heavy pointed bullet") ball bullet was 35.3 mm (1.39 in) long, boat-tailed, and very well made.[13] It was lead filled, had a gilding-metal-plated jacket, and weighed 12.8 grams (198 gr). It offered the best aerodynamic efficiency and external ballistic performance of any standard rifle bullet used during World War II, with a G1 ballistic coefficient between 0.593 and 0.557

Another:

http://omegacrossroads.com/GunCabinet/8X57/8mmMauser.htm

Ballistic Coefficient

Bullet Mach II Mach I Sub-sonic

154gr Flat Base FMJ 0.321 0.337 0.329

198gr Boat Tail FMJ 0.547 0.584 0.539

Edited June 12, 2011 by firebugs

[firebugs]

MAS 36 and FM-29 - 139gr bullet @ 823m/s

1000m 100 round total energy- 31970J

Average energy per shot- 319.70J

Resulting BC on www.jbmballistics.com- .309

In my 10-round test I got .306 and rounded down to .30. .306 vs .309 = 99%+ the same. Again, there was about a 10J spread from min. to max (317 to 327. The majority were 318 or 320). I don't think it's necessary to do another 100 rounds at any other range.

I ran 50 hits from the FM 29 on the same target and the min/max and mean values were the same. Now the search for historical values...

My honest opinion is that the MAS/FM rounds in-game are closest to the real values that they should have. I would estimate the real bullet's BC being between .340 and .390 based on my experience with .30 cal bullets (I've shot just about every commercially available .30 cal bullet, most of them beyond 500yd). At the high end of that spectrum you're looking at about an 80J increase in energy at 1000m, and it would shoot a quarter-degree flatter trajectory out to 1000m.

It's really close. I mean in all honesty, within the ~650m range where EI actually render, there's no practical difference. Even with bullet drop and flight time taken into account it's really close.

This is a pretty stark contrast to the Mg34. Even with a .30 estimated in-game BC, it's still performing markedly lower than how it should. The jump from .30 to .540-.590 is MUCH bigger than from .309 to .340.

[firebugs]

It is also interesting to note that the Matilda's Co-ax 7.92x57mm BESA MG has a BC of somewhere right around .50 (100 round test yielded average of 695J per shot @1000m). It fires the same caliber round as the K98 and MG34.

The rounds to the right of the big (15mm BESA) round is a british manufactured 7.92x57mm round (the last two are a .303 brit and 7.62 NATO). Mk IIz Ball 198 grain FMJBT @ 745m/s Almost exactly what the Germans used.

The various panzer co-ax MG's match the infantry MG34 (.306).

[chiapet]

there anything I can do to help with this?

[firebugs]

Gophur has taken an interest in this, but its on the back burner, as it were. Less important than many other issues in the game.

Best thing that can be done to help is research for any ballistic data on the calibers and ammo used in wwiiol.

Unfortunately I'm 2000 miles from home with no access to my books, and more importantly my guns and ammo to get real data with. I've also recently moved and a, awaiting internet connect (posting from phone).

[fxmmauser]

Do you know if the rounds the german sniper has are the normal k98 rounds or the 'effect-firing' sS round that had better long range ballistics ?

[wittmann]

The 8x57mm 198 grn FMJBT round used by the LW was of a higher velocity ie Mach II and developed a BC of .524 These rounds were not permitted to be used by ground forces with the exception scout/observer units for ranging purposes. Snipers commonly used these HV rounds for an additional 100 -200 meters range and devastating wounds. The K98k as used in the game was a Karbine with a shorter barrel than previous M98s. This was a result of the Treaty of Versailles which limeted Germany to short barreled rifles. In the early 1930s Germany developed the Kar98 or K98k to comply with this treaty. The bore size was increased from .318 to .323 and different propellants were used. The BC of these rifles and the new ammunition was in the range of .32 to .34 with the 154 grn flat base bullets.

[fxmmauser]

This what it says on Wiki:

The German standard sS (schweres Spitzgeschoß—"heavy pointed bullet") ball bullet was 35.3 mm (1.39 in) long, boat-tailed, and very well made.

It was lead filled, had a gilding-metal-plated jacket, and weighed 12.8 grams (198 gr). It offered the best aerodynamic efficiency and external ballistic performance of any standard rifle bullet used during World War II, with a G1 ballistic coefficient between 0.593 and 0.557 (ballistic coefficients are somewhat debatable). When fired at the typical muzzle velocity of 760 m/s (2,493 ft/s) out of a 600 mm (23.6 in) barrel the sS bullet retained supersonic velocity up to and past 1,000 m (1,094 yd) (V1000 ≈ Mach 1.07) under International Standard Atmosphere conditions at sea level (air density ρ = 1.225 kg/m3). Even by contemporary (2010) standards 1000+ m (1,094+ yards) effective range is quite remarkable for a standard military rifle round.

During World War II German snipers were issued with purpose manufactured sniping ammunition, known as the 'effect-firing' sS round. The 'effect-firing' sS round featured an extra carefully measured propellant charge and seated a sS full metal jacketed boat tail projectile of match grade build quality, lacking usual features such as a seating ring or cannelure to further improve the already high ballistic coefficient.

[firebugs]

Do you know if the rounds the german sniper has are the normal k98 rounds or the 'effect-firing' sS round that had better long range ballistics ?

In wwiiol, every variant of the k98 (sniper, sapper, grenadier, mortar, and whatever para variants) all hhave the same ballistics.

745m/s and .21 G1 bc.

all of the german 8x57mm machineguns use 755m/s and about .31 G1 bc.

The british 8x57mm BESA coax in the matilda mk2 has a G1bc around .50-.52

the brit mk2z 8mm ball ammo was pretty much a carbon copy of the german ss patrone ammo.

3 different guns all with more or less the same ammo, but wildly varying ballistic coefficients.

I have read about the sniper sS ammo, but have even less info on it. Next time I'm home ill chheck through my k98k sniper books. I also remember reading about german snipers using incendiary ammo...

I also managed to snag some german wwii ammo locally, pulled the bullet and carefully measured it, and plugged the numbers into jbm, it suggested a BC somewhere around .560, more or less what about every source I've found says (somewhere between .547-.590)