.50's deserve a buff

[dovah4]

Because the guns weren’t nose mounted on most planes, I mean. I’m %99 sure cannon mounted spitfires had convergence within the ranges they thought they were the most likely to see enemies.

[dovah4]

I whole heartedly believe platform affected accuracy. The P-47 was a very stable platform. Look at the cone of dispersion for each side of the gun.

Spoiler

It seems there is a possibility of fixing dispersion (of the cones) by adjusting the convergence of each gun to co-align with what you’re shooting with considering the P-47 shows the dispersion cones completely lined up on the bottom. But for a lot of aircraft, it might be not worth it to do that because you want to have a field of fire for your enemy.

[AlvisWisla]

Cause that’s the average engagement range of enemy aircraft…
Convergence =/= bad/good guns & munition.
After all, WW2 was the war of over 400 aircraft in the same 60km airspace.

[KillaKiwi]

I read that Spits and Hurricanes had convergance of 400m early on but then put it at 150m since the 7.7mm MGs were otherwise ineffective.

If pilot armor was never invented, firing 150-200rds per second would have been totally lethal at that range but with armor protecting the pilot, it was pointless to fire at such range, were single bullets had little chance to cause any serious damage.

[KillaKiwi]

@Pecanin

In US testing reports from 1941 they say that.50 cal are ineffective past 400 m since pen value for normal round would be around 3 mm at 450 m.
Peak pen value is 18 mm at 150 m but after that for every 50 m it loses around 3 mm of pen

I’m just gonna disprove this real quick with the German penetration data for the MG 131 firing a ligther round at less velocity:

Spoiler

You see that the weaker 13mm AP round penetrates 19mm at 100m and still 7mm at 500m, while carrying much lower KE at any range than US .50cal AP rounds, which are also more aerodynamic.

[Loofah]

Do we have accurate data for muzzle velocity etc.? I know how “reliable” German handbooks are.
96g would make it a bit more ballistically superior, I guess. But I would also expect lower MV, and unlike Germans who tested multiple configurations for MG151/20, for Soviet shells it seems like we have some “handbook” or “openly published” numbers, that can as well be unreliable.

Anyway, Shvak is horribly overperforming ballistics-wise and even tracer base bleed effect is not enough to explain this.

If the damage at least scaled down with the distance. But nuh uh.

And on .50 cal ballistics - yeah,. it’s a boattailed relatively heavy bullet, it has all the reasons to keep going at high speed.

BTW Breda should have a lot better ballistics than Mg131 due to better bullet design. Hope it’s reflected in game.
I wonder why did Germans go with the most braindead design for their ammo, while standard kar98k bullet was designed with excellent long range ballistics for its caliber. It’s like they did not care about distance longer than 400m.

[CinnamonToePunch]

Bring a SOURCE. Stop arguing with your feelings.

[KillaKiwi]

@Loofah

BTW Breda should have a lot better ballistics than Mg131 due to better bullet design. Hope it’s reflected in game.
I wonder why did Germans go with the most braindead design for their ammo, while standard kar98k bullet was designed with excellent long range ballistics for its caliber. It’s like they did not care about distance longer than 400m.

Well, the MG 131 boost some pretty good firepower for the weight at the cost of range.
But for most pilots, they wouldn’t be able to make use of longer ranges anyway and the closer you get the higher the chance of hitting the target.

@Loofah

Do we have accurate data for muzzle velocity etc.? I know how “reliable” German handbooks are.
96g would make it a bit more ballistically superior, I guess. But I would also expect lower MV, and unlike Germans who tested multiple configurations for MG151/20, for Soviet shells it seems like we have some “handbook” or “openly published” numbers, that can as well be unreliable.

I have two Russian documents. One snipet showing some ballistic data for aircraft guns and the T-60s firing table.
But it just shows the time for the shell to reach certain distances.
Compared to the MG 151 Mineshells it does so quicker.

Of course we don’t know the ammo type for the ShVAK, only that it’s supposed to be 815m/s:

Compared to a pretty fast 20mm Mineshell:

The Mineshell slows down much quicker.

The T-60 firing table only has a single decimal place. So the firing times are less accurate but it says 2.3s for 1000m for rounds fired at 800m/s.

[Loofah]

Well, not that much.
800m in 1,59 vs 800m in 1,95 for mineshell.
1000m in 2,8 vs 2,21. Yes, Shvak is going stronger. But not that much stronger it seems. The initial speed bleed is substantial and I don’t think a 900+m shot in a tailchase should be viable.
Although Shvak seems to barely slow down past 800m. Which is pretty interesting. I mean, between 800 and 900 and 900 and 1000 it’s almost the same flight time, which is extremely weird.
It probably means Shvak has a lot better transsonic and subsonic ballistics than M-geschoss, while at supersonic it’s doing actually a not-so great job!

But it’s awesome, I’ll type this into excel and get exact speeds + the speed bleed at 955m/s compared to 815m/s!

And regarding MG131 - all I’m saying is that with Breda’s bullets it would have longer effective range and shorter flight time. MG131 had very stable, well designed and devastating AP - punching full caliber hole while virtually ignoring aircraft skin. It was well designed from terminal ballistics point of view. But the shape, lack of boat tail… well, I guess they wanted the MG to kinda mirror the MG151/20, so better ballistics were actually counter-productive.

[Sawonian]

in the game US 50 cals have 20mm flat pen at 500m.

so… nerf US 50cals?

[CinnamonToePunch]

This guy just made up data.

[SpardaSon21]

Meanwhile, I have a US Army manual!

8 inch groups at 500 yards is extremely solid for any HMG, even in modern times. There’s a reason why skilled Sabre pilots in Korea were able to land shots on MiG’s at up to a kilometer once the radar gunsight got a lock.

[KillaKiwi]

But I think that’s data for the M2HB with a 45" barrel compared to the aircrafts 36".
It’s longer and heavier, probably resulting in less vibriation.

I also wondered how they made that 2km shot in Vietnam but I guess the aircraft AN/M2 is just not really built for accuracy.

Of course one must also considerer the circumstances. A long burst from an aircraft gun, firing with a high RoF, is going to heat up the barrel, particular when it’s a lighter barrel, resulting in much greater dispersion comapred to controlled short bursts from a ground MG.

@SpardaSon21

Here’s the Berezin in comparison:

With the AN/M2 firing the round at 865m/s, the ballistics are probably very similar.

[KillaKiwi]

@Loofah

Well, not that much.
800m in 1,59 vs 800m in 1,95 for mineshell.
1000m in 2,8 vs 2,21.

But that’s a big difference.

I generally consider 0.5s and lower the optimal time for a high chance to hit and 1s the maximum of being able to make reliable hits.
Of course when the target is flying straight, you can also hit at ranges that lie outside 1s travel time.

For the MG 151/20 (and MG 131), 300m and lower is ideal while at 500m and more it’s getting increasingly difficult to land hits with Mineshells or 13mm rounds.

The 12.7mm has an easy time hitting at 400m but can also hit up to 700m.

Bullet drop also plays a role, which makes it rather difficult for the MG 151/20 and MG 131 to land shots past 500m, since they slowed down so much that they just keep droping more and more.

[Loofah]

That’s not as big of a difference as I though, that’s all.
Still it’s significant.

But interesting stuff happens once it hits transsonic. It’s clear that M-geschoss has horrible transsonic ballistic coefficient. At supersonic there’s not THAT big of a difference.
Which leads me to believe M-geschoss may lose stability once its speed drops under mach 1, and then it simply starts to wobble and bleeds even more speed.

[KillaKiwi]

	ShVAK 815m/s				MG 151/20 790m/s
Range	Time	Delta Time		Range	Time	Delta Time	Velocity
100m	0.13	0.13		100m	0.136	0.136	685m/s
200m	0.27	0.14		200m	0.294	0.158
300m	0.43	0.16		300m	0.479	0.185
400m	0.61	0.18		400m	0.696	0.217
500m	0.82	0.21		500m	0.952	0.256	363m/s
600m	1.05	0.23		600m	1.249	0.297	314m/s
700m	1.31	0.26		700m	1.588	0.339
800m	1.59	0.28		800m	1.965	0.377
900m	1.89	0.30		900m	2.371	0.406
1000m	2.21	0.32		1000m	2.792	0.421	234m/s
1100m	2.55	0.34
1200m	2.91	0.36

Speed of sound is 343m/s at sea level.

[KillaKiwi]

	MG 151/20 790m/s					MG FF/M 695m/s
Range	Time	Delta Time	Velocity		Range	Time	Delta Time	Velocity
100m	0.136	0.136	685m/s		100m	0.155	0.136	597m/s
200m	0.294	0.158			200m	0.337	0.182
300m	0.479	0.185			300m	0.551	0.214
400m	0.696	0.217			400m	0.801	0.250	370m/s
500m	0.952	0.256	363m/s		500m	1.093	0.292	319m/s
600m	1.249	0.297	314m/s		600m	1.428	0.335
700m	1.588	0.339			700m	1.801	0.373
800m	1.965	0.377			800m	2.203	0.402
900m	2.371	0.406			900m	2.632	0.429
1000m	2.792	0.421	234m/s		1000m	3.052	0.420	231m/s

[Loofah]

Niiice, thank you very much.
Wonder what kind of shell is that.
Anyway, I’m kind of surprised by the 815m/s speed. Especially when MG151/20 was able to achieve 720m/s with 117g shell, I kind of assumed the theoretical capabilites od MG151/20 were very similar (probably because I looked at 90g and 800m/s muzzle velocity, both too low compared to real Shvak ammo - it’s also velocity vs momentum kind of problem).

But now I understand Shvak was higher powered weapon. Not by much, but coupled with superior ballistics, it made a noticeable difference, in WT this should translate into effective range higher by about 20%, and wirh a ton better ability for super long range shots.

[KillaKiwi]

The muzzle velocity of the ShVAK remains a bit of a mystery.

Muzzle velocity of 20mm ShVAK shells

If test were carried in out in 1941 with a 1250mm version, this could imply that the gun was taken from an IL-2 ground attack aircraft, since in 1941 I can’t recall any other aircraft that would use a 1250mm barrel version of the ShVAK that the Germans could have encountered. The barrel might have been somewhat worn out and the AP shell might have been heavier then in later productions. Which just makes one thing clear, that the 91g shell would be 20-25m/s faster out of the short barrel compa…

In general both produce roughly the same muzzle energy.
If we consider the 96.5g API being fired at 800m/s compared to the MG 151/20 El. firing a 117g AP round at 720m/s.

ShVAK used 18g of propellant powder, MG 151/20 around 18.5-19.5g but the MG 151/20 has a much shorter barrel with 1100mm compared to the ShVAK with either 1250mm or 1540mm.

[KillaKiwi]

	ShVAK 815m/s				MG 151/20 IT 720m/s
Range	Time	Delta Time		Range	Time	Delta Time	Velocity
100m	0.13	0.13		100m	0.145	0.145	660m/s
200m	0.27	0.14		200m	0.303	0.158
300m	0.43	0.16		300m	0.477	0.174
400m	0.61	0.18		400m	0.666	0.189
500m	0.82	0.21		500m	0.874	0.208
600m	1.05	0.23		600m	1.101	0.227
700m	1.31	0.26		700m	1.348	0.247
800m	1.59	0.28		800m	1.616	0.268
900m	1.89	0.30		900m	1.905	0.289	334m/s
1000m	2.21	0.32		1000m	2.215	0.310	312m/s
1100m	2.55	0.34		1100m	2.545	0.330
1200m	2.91	0.36		1200m	2.895	0.350	279m/s

Let’s have a look at the FI-T and IT rounds. Their weight and tracer should make them aerodynamically superior compared to the lighter ShVAK ammo.

And in fact, despite the round being much slower at first, it reaches 1200m at around the same time.