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#21 Jussi Saari

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Posted 02 May 2009 - 0349 AM

What was this "special" HEAT ammo?

Was it designed to deal with the IS/T-10?


M431 I would think? That one would have had enough penetration to deal with IS-3/T-10, but it could have trouble fuzing reliably (given that it had to come from almost from straight ahead to work on the T-55 glacis.

#22 Old Tanker

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Posted 02 May 2009 - 0914 AM

What was this "special" HEAT ammo?

Was it designed to deal with the IS/T-10?


I have no idea the rounds designation but yes it was to deal with the Russki heavies . All that I know is a team came onboard our invasion ship and changed a cam in the analog computer and issued each tank 2 rounds.
We were told that 5,000 Russian troops in Cuba ( actually 50,000) including one heavy tank brigade.

#23 Nikolas93TS

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Posted 07 January 2013 - 0939 AM

What was this "special" HEAT ammo?

Was it designed to deal with the IS/T-10?


M431 I would think? That one would have had enough penetration to deal with IS-3/T-10, but it could have trouble fuzing reliably (given that it had to come from almost from straight ahead to work on the T-55 glacis.


Jane's gives approximately 190mm penetation of steel at a 60 degrees angle at any range (which at optimal 0° would be around 380mm) which means they could engage any tank of the era with certain confidence if fuze was working.Jane's also give effective range of only 1,000m.

#24 bojan

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Posted 07 January 2013 - 1204 PM

Jane's mixed apples and oranges again.

190mm @ 60deg is data for older 90mm M348 heat (we got it with M47s originally, but after delivery of first batch of M431 in 1956. it was removed from combat load and placed to reserves to be used for training/emergency war stock).

Local penetration data:

110mm @ 60deg from vertical (30deg from horisontal)
140mm @ 50deg from vertical (40deg from horisontal)
170mm @ 40deg from vertical (50deg from horisontal)
190mm @ 30deg from vertical (60deg from horisontal)
220mm @ 0deg from vertical (90deg from horisontal)

M431 penetrated:
150mm @ 60deg from vertical (30deg from horisontal)
190mm @ 50deg from vertical (40deg from horisontal)
230mm @ 40deg from vertical (50deg from horisontal)
260mm @ 30deg from vertical (60deg from horisontal)
300mm @ 0 deg from vertical (90deg from horisontal)

So Jane's managed do mix two different ammo and two different criteria.
It is not only case, it also states that Yugo 76mm M74 penetrates 120mm @ 30deg, 90mm M74 penetrates 150mm @ 30deg and 100mm penetrates 195mm @ 30deg, which is technically corect if you note that angle is measured from horisontal (German influence, only ditched in '80s), not the usual vertical.

Edited by bojan, 07 January 2013 - 1214 PM.


#25 BabyOlifant

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Posted 07 January 2013 - 1234 PM

So as long as HEAT fuses, it will basically penetrate LOS thickness regardless of the angle. I had heard that, but this is a better illustration of it.

#26 Przezdzieblo

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Posted 07 January 2013 - 1250 PM

bojan, there must be some mistake, M431 could not been delivered to Yugoslavia in 1956. In 1958 it was still in development phase as T300. I guess E59 variant was standarized as M431 not earlier than in 1960s.

The first 90 mm HEAT for US tank guns was T108, started in 1950. Orginally penetration of 5 inches armour at 60 degrees obliquity was required - no idea if ever . E40 variant was standarized as M348 but it proved to be inaccurate because of design and quality issues. Modified M348A1 (T108E46, circa 1957) was not very better. T300 was started in 1953, mainly because of problems with T108.


Old Tanker, maybe do you remember if those "special" HEAT-T rounds were spike-ended like one below? Posted Image

#27 AdmiralB

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Posted 07 January 2013 - 1313 PM

Does that diagram indicate a slip ring? Fin-stabilized, so I reckon there's some sort of spin control?

#28 Przezdzieblo

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Posted 07 January 2013 - 1350 PM

M431 got nylon slip band. Do not know details about methods of spin control in case of T108 series, but guess might be similar.

#29 bojan

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Posted 07 January 2013 - 1610 PM

bojan, there must be some mistake, M431 could not been delivered to Yugoslavia in 1956. In 1958 it was still in development phase as T300. I guess E59 variant was standarized as M431 not earlier than in 1960s.

I will double check it but I am pretty sure that first batch of 3200 (thats onlz 10/tank!), was delivered with some other armament soon after Soviets invasion of Hungary. Only doubt I have is that they were designated T431 in our documents... Which I assume (yeah I know :) ) to be M431 as there was no 90mm T431 HEAT. Could it be those were original T300 and designation somehow got f***ed up (would not be 1st time, one official document has "49mm Bofors"...?
BTW, HEAT ammo used in tests vs T-54 was definitely M431, so it was available in 1962 when those were done.

The first 90 mm HEAT for US tank guns was T108, started in 1950. Orginally penetration of 5 inches armour at 60 degrees obliquity was required - no idea if ever

5" @ 60deg is close to my tabellar 110mm @ 60deg for M348.

#30 Guest_Jason L_*

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Posted 08 January 2013 - 0040 AM

bojan, there must be some mistake, M431 could not been delivered to Yugoslavia in 1956. In 1958 it was still in development phase as T300. I guess E59 variant was standarized as M431 not earlier than in 1960s.

The first 90 mm HEAT for US tank guns was T108, started in 1950. Orginally penetration of 5 inches armour at 60 degrees obliquity was required - no idea if ever . E40 variant was standarized as M348 but it proved to be inaccurate because of design and quality issues. Modified M348A1 (T108E46, circa 1957) was not very better. T300 was started in 1953, mainly because of problems with T108.


Old Tanker, maybe do you remember if those "special" HEAT-T rounds were spike-ended like one below? Posted Image


Gaah.....why does it have a square cavity at the cone apex? Square apex bad for optimal penetration. :wacko:

Edited by Jason L, 08 January 2013 - 0040 AM.


#31 Przezdzieblo

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Posted 08 January 2013 - 1452 PM

Since when?

I mean, since when "we" know that square apex bad for optimal penetration? Guess it was not the "default" knowledge in shaped charge research history.

Edited by Przezdzieblo, 08 January 2013 - 1453 PM.


#32 bojan

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Posted 08 January 2013 - 1908 PM

Jason, IIRC it is not really square bottom is semi-hemisferical.

#33 Guest_Jason L_*

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Posted 09 January 2013 - 0224 AM

Since when?

I mean, since when "we" know that square apex bad for optimal penetration? Guess it was not the "default" knowledge in shaped charge research history.


That's a good question. There is a mix of flat apex and smooth, rounded apex weaponized shaped charge devices throughout the 40ies. However, I presume it was known fairly early, like in the mid-late 40ies, before the aerojet days in the US, that rounded bottom charges offered better jet coherency and consistency. That sort of square section at the apex is typically associated with interrupted shaped charge jet designs.

Jason, IIRC it is not really square bottom is semi-hemisferical.


Yeah, but is it smooth like a conventional conical liner or does it have a conical divot? Maybe they wanted the divot to throw a massive, somewhat incoherent jet tip ahead of the rest of the jet to bust through the fuse probe?

Edited by Jason L, 09 January 2013 - 0225 AM.


#34 BabyOlifant

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Posted 09 January 2013 - 0342 AM

OK, I gotta ask: What's the reasoning behind the "spike ended" HEAT ammo in the style of the above cartridge? It is clearly not designed with favorable aerodynamic properties in mind.

#35 Guest_Jason L_*

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Posted 09 January 2013 - 0409 AM

OK, I gotta ask: What's the reasoning behind the "spike ended" HEAT ammo in the style of the above cartridge? It is clearly not designed with favorable aerodynamic properties in mind.


It's a stand-off probe that contains the piezoelectric impact sensor that triggers the base fuse. You can make it more aero with an thin faring but not necessary.

#36 Przezdzieblo

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Posted 09 January 2013 - 0444 AM

Spike-nose is not only for stand-off and anti-ricochet purposes, but also it is a method of stabilization of quite fast, fin stabilized projectiles. Presence of spike helps to reduce length of tail with fins - and vulnerability of tail, very prone to damages during firing and flight, were one of the reasons of failures in 90 mm HEAT-T T108 programme.

#37 bojan

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Posted 09 January 2013 - 0637 AM

Spike-nose is not only for stand-off and anti-ricochet purposes...


Ironically spike nosed M431 worked up the 60deg, convencional nose BK-5M worked up the 65-70deg... More issue of fuse then nose shape.

...and vulnerability of tail, very prone to damages during firing and flight, were one of the reasons of failures in 90 mm HEAT-T T108 programme...


IIRC main culprit was muzzle break, hence the change in muzzle break shape at one moment. M438 was also not useable in 90mm M3A1 guns in M36 TD, even our local M74 HEAT required removal of it's muzzle breaks when it was introduced.

For comparing, 100mm M69, BK-5M (BK-5 is generally same but liner is steel and it lacks wave shaper) and 90mm M74:

Posted Image
Posted Image
Posted Image

BTW, all 3 have two shaped charges in warhead, spitback fuse is a miniature (less then 10mm diameter) semi-hemispherical shaped charge.

Edited by bojan, 09 January 2013 - 1901 PM.


#38 BabyOlifant

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Posted 09 January 2013 - 1300 PM

But there's no reason that couldn't be covered with an aeroshell, which would help ballistic coefficient and hit probability significantly, I should think.

#39 Guest_Jason L_*

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Posted 09 January 2013 - 1316 PM

But there's no reason that couldn't be covered with an aeroshell, which would help ballistic coefficient and hit probability significantly, I should think.


Following what Przezdzieblo said, it's quite possible that the shoulder creates a desirable effect on the center of pressure from the perspective of quickly stabilizing precession of the round on leaving the muzzle. Never really thought about it before, but it makes sense.

Also, IIRC, the edge of the ring is an alternative sensor element as well, something not as successful if you put a fairing.

Of course you can make a round with a better aerodynamic front end. Multipurpose rounds with fusing/sensors more sophisticated than simple contact tend to encase them in a nose cone ahead of the liner and explosive. Note the changes in the A1 over the base M830.

#40 shep854

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Posted 09 January 2013 - 1322 PM

The 'spike' looks awkward, but at supersonic speeds, won't the shock wave produced by the spike act as its own fairing?




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