Main Gun Ammo - Revisited

[Stefan Kotsch]

7 hours ago, KV7 said:

OF19 should produce not very good results at least vs. infantry,

From 1986 we completely swapped our OF19 for OF26. The powder is more powerful when detonated. But there were no grooves or preformed elements or anything like that. However, the OF's task was not to combat infantry. This must be taken into account. Main targets should be APC, IFV and so on as well as earth bunkers and such targets.

[old_goat]

8 hours ago, KV7 said:

OF19 should produce not very good results at least vs. infantry, given it uses a thick steel casing without any scoring or preformed elements, and so should produce a small number of large fragments.

Yes, he says they even found an exploded shell that was basically split into two large pieces. Mostly the explosion forms large elongated saber like fragments. Not ideal. But still, these shells are devastating. 

[JWB]

19 minutes ago, old_goat said:

Not ideal. But still, these shells are devastating.

Catastrophic against AFV running gear.

[bojan]

Vs AFVs in general. Hit on armor thinner than ~50-60mm (practically all western MBTs side hull) produces major cracks in armor. Even 80mm sides of T-xx are not immune (from Harkonnen's blog):

Type of damage dealt, with large cracks in armor, deformations etc is also not easy to repair in field conditions and often tank is written off as repairs are either not economical or require too much effort and spares that are better spent elsewhere.

Edited December 11, 2023 by bojan

[KV7]

12 hours ago, Stefan Kotsch said:

From 1986 we completely swapped our OF19 for OF26. The powder is more powerful when detonated. But there were no grooves or preformed elements or anything like that. However, the OF's task was not to combat infantry. This must be taken into account. Main targets should be APC, IFV and so on as well as earth bunkers and such targets.

This is understandable, but still it could be improved on a little. Improving fragmentation of the HE round could be achieved with  little tradeoffs, so the general purpose role of the munition is not a good reason not to do it.

Against vehicles, HEAT or AP will work at least as well or good enough, so the only issue is against structures, where HE is really superior. So another option would be to issue a APHE type round for use against strong bunkers and tough buildings etc.  and a high capacity FRAG round for hitting everything else.

I am also a little confused by the relation to doctrine, as my understanding was that a major role of armour in the USSR doctrine was overrunning infantry positions, hence the relatively large HE loadouts, and the increased value given to second line tanks that might not be very adept at tank vs tank battles but can undertake the CS/assault role admirably.

[Interlinked]

Formation of saber-shaped fragments, or splinters as they're called, is what happens with all artillery shells, except maybe for the most modern ones in use nowadays. But back then, the lack of preformed fragments was pretty much universal for such shells.

Tank HE-Frag shells were certainly intended for eliminating groups of infantry, and also the somewhat vaguely defined "ATGM emplacement". It's just that, in general, it's more justified to use it on something that the coax can't easily handle.

[KV7]

I agree it seems to have been common, but to me a little perplexing, given it is so easy to get a vastly improved effect.

Even is scoring was ruled out by the need to maintain shell wall strength or cost worries, replacing some small fraction of the HE filler with steel balls or similar would give a vast improvement in fragment number and then effect vs infantry, at the cost of a small increase in mass and slightly reduced blast effect.

Also regarding the shell walls, it would seem that for tank rounds (but not long ranged artillery, which needs high velocity) it would likely be optimal to reduce wall thickness a little even if this requires using a reduced charge, which then allows for more filler and/or fragments. In theory there would be reduced chance of hitting moving targets at long range, but this is a sort of niche worry (and in the case of unarmored vehicles, perhaps offset by better fragment effect).

I imagine the issue of shell wall strength is the main explanation, as we see grenade, mortar and rocket rounds using preformed fragments pretty early, and these are applications where getting sufficient wall strength is more trivial.

As for using the coax, it would seem to not really be sufficient firepower for many targets or roles.

[Wiedzmin]

13 hours ago, bojan said:

Even 80mm sides of T-xx are not immune (from Harkonnen's

125mm HE which didn't blow-off external fuel tube? And didn't torn off whole rear roof section? Omitting the fact of absence of any fragments signs and no fin marks on armor looks strange

 

As for part of side armor where piece was torn off, its 40mm thick miled part of ring protection 

[Stefan Kotsch]

HE-FRAG like the OF19/26 are intended to break through APC armor and detonate inside with a slight delay. That's why the detonators have a igniter cap. For slightly delaying the detonation. And besides. In the T-64/72/80/90 you will not load an OF into the magazine that does not have a igniter cap. And no commander scrapes the cap while loading.

If I add grooves or something similar, I reduce the statics of the shell casing. Penetrating light armor becomes more difficult. Yes I know. It's all a compromise. The focus at that time was fighting APC, IFV and so on.

Today there is OF82 TELNIK. 

[bojan]

11 hours ago, Wiedzmin said:

125mm HE...

What do you think caused damage?

[Stefan Kotsch]

12 hours ago, Wiedzmin said:

Omitting the fact of absence of any fragments signs and no fin marks on armor looks strange

I agree with that. The typical splinter corona is completely missing. The rubber on the support roller is undamaged, although it is located directly at the impact hole. Strange stamping mark.

Maybe 57mm AP or something in that 'price range'?

[Wiedzmin]

2 hours ago, bojan said:

What do you think caused damage?

 

2 hours ago, Stefan Kotsch said:

Maybe 57mm AP or something in that 'price range'?

57mm AP will pen both without any trouble, 57mm HE on the other hand can do such damage, but usually also leave fragments signgs + point of contact(if shots was from close range) usually get  tarnish colors + support roller doesn't have damage even on rubber(but one roller completely shot off), maybe 30mm HE ? it's sometimes can do such damage but...

 

examples of 

30mm HE(not sure about the one which hit 2S3)

 

 

 

mild steel plate tests by finns 

 

 

57mm HE

 

90mm HE

 

125mm and some other HE's

 

 

 

or maybe T-80 in question have 1x125mm HE In center, and other hits is something else, 30mm AP-T from far distance ?

Edited December 12, 2023 by Wiedzmin

[bojan]

Maybe 30mm AP?

[Junior FO]

...

Edited September 23, 2024 by Junior FO

[Perun]

Thanks mate 😉

15 hours ago, Junior FO said:

https://ufile.io/3wv431nj

https://ufile.io/lmsb46w8

 

[old_goat]

Now about the 125mm HEAT. Most of what he says is well known, but still a well made, and interesting, informative video.

 

[Peasant]

Quote

The mass of cap + windshield of the M62 projectile is 18% of its total mass. From this comparison it looks like the percentage for the 90mm shell is even higher, due to the cap itself being thicker and the penetrator’s body shorter.

18% of 7kg equals to 1.26kg. Scaling this up times (90/76)^3 = 1.66 we get 2.09kg, the lower bound for the cap + windshield assembly for M82 projectile. Which is 19.1%. The actual value might be ~22%.

If you're wondering, I'm not leading this to anything in particular, just wanted to share this information with people.

[Peasant]

Does anyone have some reliable physical data on the 120mm APDS for Conqueror's gun?

If we scale up the 20pdr APDS Mk.III design to 120mm caliber, we get: ~9.39kg 76mm diameter subcaliber shell with a 6.15kg, 58mm core.

 

Edit: actually, it can't be that large (the tungsten core, I mean). 

The 20pdr APDS penetration from british sources is about ~330mm/0° at 1000yards, while that of the Conqueror is 446mm.

 

The penetration ratio is smaller than the caliber ratio: 446/330mm = 1.35, and 120/84mm = 1.43.

Not to mention that the Conqueror's gun has a higher muzzle velocity with APDS that the 20pdr with APDS. 

 

Therefore, this 120mm APDS design does likely have a proportionally smaller core than the 20pdr.

Edited June 12, 2024 by Peasant

[Wiedzmin]

6 hours ago, Peasant said:

while that of the Conqueror is 446mm.

Really doubt that is was capable of any pen as high as this, core will shatter before it reach such numbers, even considering the fact that's it's more ojival than l28 which had critical fractures velocity around 1350ms or so IIRC 

 

About 84mm apds, here is swedish trials 

 

 

Edited June 12, 2024 by Wiedzmin

[Peasant]

There is no need to speculate, we have already seen that the 20pdr APDS can reliably perforate 300mm at 0-20° at striking velocity of ~1350m/s:

300mm is ~3.57 calibers. The striking velocity of the 120mm L1 APDS at 1000yards is close to that of the 20pdr at 100m tested here. Now admittedly the 20pdr did not quite reach the performance listed in the British document but that might be because this is 20pdr APDS Mk.I (or 2?) used here and not the Mk.III

 

@bojanI suggest you always keep things in perspective when looking at gun's penenetration figures. For example, 100mm/0° is a lot of penetration for a 37mm gun, but not for a 75mm one. Therefore, I don't find it that hard to believe that a 120mm APDS can perforate 400-450mm of flat armour, especially one with an ogival head. 

 

 

P. S. Anyone here speaks Swedish? 

Edited June 12, 2024 by Peasant

[bojan]

3 hours ago, Peasant said:

...

@bojanI suggest you always keep things in perspective when looking at gun's penenetration figures. For example, 100mm/0° is a lot of penetration for a 37mm gun, but not for a 75mm one. Therefore, I don't find it that hard to believe that a 120mm APDS can perforate 400-450mm of flat armour, especially one with an ogival head. 

??? I said nothing about 120mm APDS penetration.

[Wiedzmin]

9 hours ago, Peasant said:

reliably perforate

Plattenfestigkeit between 67-77 is kinda...plastilin, no ?

[Peasant]

6 hours ago, bojan said:

??? I said nothing about 120mm APDS penetration.

My bad, my eyesight is not what it was, I mistook @Wiedzminfor you.

 

54 minutes ago, Wiedzmin said:

Plattenfestigkeit between 67-77 is kinda...plastilin, no ?

Yes, thats ~197 - 226 BHN. I don't know why they bothered using those plates. But the 300mm plate was 82kg/mm2 (242 BHN) which is adequate for such thickness. 

[Wiedzmin]

Knowing only hardness is not much, but still prefer to see german tests on TL plates instead of this