Yes. According to German data. It’s because jacketed bullets, will get destabilized very easily after impacting any material at oblique impact.
The German 13mm round doesn’t have a copper jacket but is like a miniature cannon shell made from hardened steel with a driving band.
The center of gravity is also near the front, due to the large tracer cavity, which keeps the round facing forward instead of turning sideways.
The downside are the worse ballistic performance, since the .50cal is both more pointy and also boat tailed. But the tracer makes up for that to some degree. 13mm API was only used for a short period. I suspect because it must have had unusable ballistic performance, since it would have even worse ballistics than AP-T.
13mm AP-T compared to 12.7mm AP (from German document)
Numbers in brackets are the armor penetration values at 100m, for a high hardness steel plate (450 BHN), 2m behind a 2mm dural plate sloped at 70°.
A 7.92mm or 7.7mm AP round will penetrate 4mm in comparison.
True if it performed like real life, where Finn’s ambushed T-26 with 0.50cal at close range and made no impression, it would be unusable like it is in reality.
But maybe they should have thought of that before giving 12.7 autocannon performance.
In game - yes. But apparently IRL the bullet design was pretty smart for destroying planes, although, just like with other German air to air weapons, some decisions are harder to understand :)
Pretty sure Finn’s used Boys AT Rifles to some effect against T-26s and BTs.
Both are vulnerable to .50cal rounds after all.
And you can see from the document you posted that a US 50cal. AP will punch through 5/8" (15.875mm) even at 30° with roughly 2730fps (832m/s).
Which means a penetraten range of around 100-500m, depending on impact angle.
All of Germanys guns use Full steel Driving band ammo, with exception to 7,92mm, tho that had the Pz.Geschoss developed, which is a 10g Full steel Copper driving band steel. Mainly as Air to air Ap, duo to above mentioned better performance after penetrating aircraft skin.
But also was used as a cheaper alternative in the 7,92x94mm case with the Pz.B.38 and 39 as well as EW 141 with some 1250m/s velocity.
I have another topic, which shows pretty much all German (own) used Armarments. (Or rather 3 topics, AA, General ground and Aircraft armarments) they are pinned in the dedicated place on the forum, so rather easy to find.
It’s hilarious that I routinely find your comments on youtube, haha. But it shouldn’t surprise me, it seems we zre interested in rather obscure topics :D
Anyway, I love that thread, it’s so damn informative.
BTW ever since I’ve started using stealth belt I no longer have problems with MG151/20 ballistics. Yes, they are horrible, but additional 70-80m/s muzzle velocity makes all the difference inside 500m. Finally they are in line with my expectations.
MG131.prrformed very well after oassing through sircraft skin. .50 cal did not. That’s some smart design. MG131 was not a great weapon. But it had some good festures
13mm leave no visible impact not that it doesn’t penetrate
The machine guns they have are useless because they aren’t reliable when it’s very cold.
I mean if 7.92mm Tungsten bullets could penetrate a T-26 from 100m, then so can a high velocity 13.2mm steel AP round.
From Soviet tests:
The 12.7 mm DShK penetrates 15 mm of Czech surface hardened armour on a Pz38(t) at 20 degrees from 200 meters 4 out of 12 times and from 150 meters 7 out of 9 times.
Similarly, 20 mm plates of German armour at 20 degrees in a PzIV is penetrated by the DShK from 100 meters 2 out of 2 times.
So a 12.7mm (API) will even penetrate 20mm FHA from 100m, while the the T-26 just had 15mm HHA.
A bit off topic but here’s the 15mm API in comparison.
Spoiler
As we can see, they are nearly identical and thus would behave very similiar.
I checked the ballistic table and at 500m the 15mm API would penetrate as much as 13mm from 100m (15mm).
In comparison the 15mm AP-T also only penetrate 15mm at 100m when it first goes through the airframe, since its center of gravity is around the center while the API is going to be more nose heavy.
Thus the 15mm API has really excellent AP performance for combating fighters.
Combined with the new Incendiary round, I would say that easily doubled the effectiveness of the MG 151 and that it probably was on par with the 20mm MG 151.
The 20mm MG 151 will cause more damage but it’s also less likely to score hits due to the low velocity, high drag shells.
A P-47 is still very susceptable to the armor piercing and incendiary elements of the 15mm shell, while it will tank 20mm Mineshells much better than smaller fighters.
Against large, slow targets like bombers, bigger calibers are going to be more effective, since it’s going to be easier to hit the target, negating the advantage of more hits from smaller calibers in favor for more damage per hit.
Well, the thing is that penetration isn’t something that can be generalized but greatly changes with plate thickness and armor hardness.
So for every caliber there’s a specific hardness that would result in the lowest amount of steel necessary to stop it.
But if you use the best armor hardness to protect against 20mm shells, the armor will become even more vulnerable to larger caliber shells.
Since the best way to stop a shell is by breaking it up without the armor plate shattering or pluging, but shattering and plugging becomes more likely the more kinetic energy impacts the plate.
According to German data, the 15mm AP-T penetrates 25mm of HHA (~450 BHN or 150kg/mm² tensile strenght) compared to the 24mm of US .50cal.
Likewiese the Soviet 12.7mm API penetrates 25mm as well while the API-T penetrates 23mm.
However the maximum penetration is limited here by the ballistic limit of the rounds.
Which means, that the 15mm AP-T and 12.7mm AP and API penetrate comparetively little armor and the 12.7mm API-T a lot in comparison, because they simply can not defeat armor of such hardness without breaking appart.
If the armor was softer, then the increased kinetic energy wouldn’t go to waste and the rounds could penetrate more armor.
There’s some data for the 20mm API-T fired by German AA guns, to penetrate 42mm at 100m against 125kg/mm² tensile strenght armor.
The 15mm AP-T would be able to penetrate 34mm according to DeMarre, in comparison.
I get around 27mm for US .50cal AP at PB, when just using the steel penetrator data.
While this table puts it at 28mm.
Gaijins calculator gives 20mm API-T and 15mm AP-T too little penetration in comparison, with only 37mm and 30mm at 100m, respectively.
In fairness .50cal AP would also need to have their penetration reduced from 28mm to 24mm at 100m.
In-game they have higher penetration because Gaijin uses a calculator for tank shells but uses data for jacketed bullets. Since the .50cal bullets are not made from solid steel but use a steel core, the penetration data is off in comparison.
