Yu guns vs armor tests of 1960s...

[Alvaro]

Let me make an observation. Sherman turret front is cast 90mm thick while its glacis is RHA 64mm@47º that represents a LOS of 94mm. T-34 turret front is also cast 90mm thick (curved) and LOS of RHA glacis of 90mm also. So it seems possible to compare thick plates (turrets) against the same LOS of sloped plates (glacis)

 

Well, comparing the penetration ranges for both turret and glacis forT34 and Sherman, it seems that thick vertical plates have a slight advantage over sloped plates for every gun except ZIS-3 against Sherman. This difference is increased if we considered that cast armor is said to be less resistant than RHA.

 

ZIS-2 against Sherman has identical penetration range for both turret and glacis. And as Bojan pointed, T34 armor is more effective against ZIS2 than Sherman.

 

It looks like sloped armor is less effective than equivalent weight of vertical armor against projectiles of larger calibre than its thickness.

 

When caliber and thickness are similar, ZIS2 against Sherman glacis, sloped armor is neutral.

 

There no example here of small caliber guns, but I assume that in that case sloped armor would be better than vertical. And also in that case hard armor is better, as ZIS2 seems to indicate.

 

What do you think?

 

Best regards

Alvaro

Edited December 12, 2006 by Alvaro

[DB]

It looks like sloped armor is less effective than equivalent weight of vertical armor against projectiles of larger calibre than its thickness.

 

What do you think?

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I believe that this makes sense anyway.

 

I think this makes sense from a geometric point of view.

 

Looking at the stress build-up in the armour as the round penetrates, there comes a point where an (um, terminology problem here) iso-surface intersects the back face of the armour. The point being that the stress at that surface is enough to cause a plug-like failure of the armour.

 

It's likely that this iso-surface is vaguely spherical, centred on the nose of the projectile. For a sloped surface, the first contact of this surface with the back face would be somewhat below the LOS line, and therefore the failure would occur there, before the stress level had risen enough to cause a plug failure along the LOS.

 

As a result of loss of integrity of the armour below the LOS, the projectile would be deflected into this region and perforate the target having effectively seen less armour than the LOS measurement would predict.

 

Hope that makes sense to someone other than me

 

David

[jwduquette1]

couldn't find a listing in Hunnicutt for M4A3E4 Sherman. at least not in my once over. is this the M4A3E4?

 

http://www.armyvehicles.dk/images/m4a3.jpg

[Guest bojan]

couldn't find a listing in Hunnicutt for M4A3E4 Sherman.  at least not in my once over.  is this the M4A3E4?

 

http://www.armyvehicles.dk/images/m4a3.jpg

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Yes - it was a lash-up originaly made for service in Korea, then given by MDAP. It was made from standard late model 75mm armed Sherman but with 75mm gun changed for the 76mm M1/M1A1. Often Confused for Firefly as it has a long gun in a standard Sherman turret... There were M4A1 and M4A3 based versions. Was used by Denmark (M4A3E4), Yugoslavia (M4A3E4) and Pakistan (both M4A3E4 and M4A1E4). Probably other but those are certein.

 

Here are pics of them in Yugoslavia:

http://elektron.tmf.bg.ac.yu/bojan/armor/tanks/m-4/

 

PS. A bit of trivia - those were Shermans used in Kelly's Heroes...

[Alvaro]

In Zaloga's New Vanguard Sherman book appeared with a flat mantle, like this...

 

http://www.armchairgeneral.com/photopost/d...ankfest_602.JPG

 

But perhaps Bojan can tell us which is the Yug. Sherman

 

 

Ah! I see that Bojan posted at the same time than me.

Edited December 12, 2006 by Alvaro

[Alvaro]

There no example here of small caliber guns

 

I am wrong. 88m PAk43 against 100m RHA T-54 (200mm LOS) compared with 200 cast curved front turret. Here sloped armor is quite effective.

 

Best regards

[jwduquette1]

so is the turret front on the M4A3E4 3-inches thick @ 30-degrees -- cast armor?

Edited December 13, 2006 by jwduquette1

[Mobius]

What I find interesting is the comparison to 0° penetration and 60° penetration for the APHE vs. APBC ammo.

[jwduquette1]

Let me make an observation. Sherman turret front is cast 90mm thick while its glacis is RHA 64mm@47º that represents a LOS of 94mm. (glacis)

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Ok -- let me ask this another way -- where is the 90mm turret front coming from. Or did you mean 3" @ 30-deg with an LOS thickness of 90mm?

 

Or do you mean the gunshield -- 3.5" @ 0-degrees?

Edited December 13, 2006 by jwduquette1

[Mobius]

Ok -- let me ask this another way -- where is the 90mm turret front coming from.  Or did you mean 3" @ 30-deg with an LOS thickness of 90mm?

 

Or do you mean the gunshield -- 3.5" @ 0-degrees?

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Probably the gunshield as it covers most of the center front turret.

 

But I think the data does show there is something that may be a relative weakening the glacis of the T-34. Maybe it is the hardness.

Edited December 13, 2006 by Mobius

[jwduquette1]

But I think the data does show there is something that may be a relative weakening the glacis of the T-34.  Maybe it is the hardness.

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Can you elaborate a bit more on what you mean?

[Mobius]

Guns vs T-34/85:

Glacis - 46mm @ 60deg or LOS=92mm

Front turret - 90mm, rounded. LOS=90mm

 

75mm M40 PaK40 firing AP

M39 AP (PzGr.39?) penetrates glacis @ 1300m*

M39 AP penetrates front turret @ 1000m

 

Weapons tested vs M4A3E4 Sherman

Glacis - 64mm@47deg, 250 BHN LOS=94mm

Front turret/mantle - 90mm average, 230 BHN LOS=90mm

 

75mm M40 PaK40 firing AP

M39 (PzGr.39?) AP penetrates glacis @ 1100m

M39 (PzGr.39?) AP penetrates front turret @ 1000m

 

 

vs. T-34/85

85mm ZiS-S-53 (from T-34/85) firing AP, HVAP and HEAT

BR-365 AP penetrates glacis @ 1200m

BR-365 AP penetrates front turret @ 1000m

 

vs. Sherman

85mm ZiS-S-53 (from T-34/85) firing AP

BR-365 AP penetrates glacis @ 1100m

BR-365 AP penetrates turret @ 1000m

 

There seems to be a slight improvement in penetration of the glacis of the T-34 by the rounds though there is only a 2mm LOS difference and lesser BHN for the Sherman. Note they penetrate the 90mm turrets at the same range.

Edited December 13, 2006 by Mobius

[Alvaro]

Ok -- let me ask this another way -- where is the 90mm turret front coming from. Or did you mean 3" @ 30-deg with an LOS thickness of 90mm?

It is from Bojan post on Sherman data:

 

Weapons tested vs M4A3E4 Sherman

Armor:

Glacis - 64mm@47deg, 250 BHN

Side hull - 38-51mm@0deg, 250 BHN

Front turret/mantle - 90mm average, 230 BHN

Side turret - 51mm, 230BHN

 

Best regards

[Guest bojan]

In Zaloga's New Vanguard Sherman book appeared with a flat mantle, like this...

 

http://www.armchairgeneral.com/photopost/d...ankfest_602.JPG

 

In that case book is wrong - T23 turrets as instaled on WW2 76mm armed shermans had a flat mantle, while standard Sherman had a a curved one, just like on a pics I posted...

[jwduquette1]

In that case book is wrong - T23 turrets as instaled on WW2 76mm armed shermans had a flat mantle, while standard Sherman had a a curved one, just like on a pics I posted...

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Thanks Bojan. So the Yugoslavian M4A3E4 Sherman would have had the smaller curved mantlet -- is this correct?

 

If the smaller mantlet is the case, do the Yugoslavian trials vs. the Sherman Turret Front represent range at which the mantlet is perforated or range at which the turret front is perforated? Sorry -- I'm not trying to be deliberatly dense here. It's just that I started plugging through some numbers and realized that I didnt really know which aspect of the turret was being tested -- mantlet face or turret face.

[jwduquette1]

Guns vs T-34/85:

Glacis - 46mm @ 60deg or LOS=92mm

Front turret - 90mm, rounded.  LOS=90mm

 

75mm M40 PaK40 firing AP

M39 AP (PzGr.39?) penetrates glacis @ 1300m*

M39 AP penetrates front turret @ 1000m

 

Weapons tested vs M4A3E4 Sherman

Glacis - 64mm@47deg, 250 BHN  LOS=94mm

Front turret/mantle - 90mm average, 230 BHN  LOS=90mm

 

75mm M40 PaK40 firing AP

M39 (PzGr.39?) AP penetrates glacis @ 1100m

M39 (PzGr.39?) AP penetrates front turret @ 1000m

vs. T-34/85

85mm ZiS-S-53 (from T-34/85) firing AP, HVAP and HEAT

BR-365 AP penetrates glacis @ 1200m

BR-365 AP penetrates front turret @ 1000m

 

vs. Sherman

85mm ZiS-S-53 (from T-34/85) firing AP

BR-365 AP penetrates glacis @ 1100m

BR-365 AP penetrates turret @ 1000m

 

There seems to be a slight improvement in penetration of the glacis of the T-34 by the rounds though there is only a 2mm LOS difference and lesser BHN for the Sherman. Note they penetrate the 90mm turrets at the same range.

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Could be. I'd havent looked that closely at these results. I would be surprised if these lower t/d results indicated the high hardness T34 armor to be better than the Shermans "normal" hardness RHA.

[Mobius]

I would be surprised if these lower t/d results indicated the high hardness T34 armor to be better than the Shermans "normal" hardness RHA.

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I'm not looking so much at t/d but at energy.

Could be a case of shatter gap in reverse. Where it's the armor that shatters.

[Guest bojan]

Thanks Bojan.  So the Yugoslavian M4A3E4 Sherman would have had the smaller curved mantlet -- is this correct? 

 

Yes. Clearly seen on THIS picture.

 

If the smaller mantlet is the case, do the Yugoslavian trials vs. the Sherman Turret Front represent range at which the mantlet is perforated or range at which the turret front is perforated?

 

Tests are not clear but I guess that some average was taken - note that pdocument not "90mm average" - where mantle overlaps front turret armor it would be more, where mantle and turret armor are alone that would be a bit less and finaly at the corners where armor curves to the sides it would be a lot more... My guess is that they just aimed at the center of the turret and noted range where 50% of the hits penetrated, wherever on the front turret ppenetrations were.

[Vuk]

Somewhat OT but were any tests performed against the Tip 628 and 636?

[Guest bojan]

Somewhat OT but were any tests performed against the Tip 628 and 636?

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As far as I know - No.

[jwduquette1]

The BR-271 slope effects vs. the Sherman M4A3E4's Glacis are only about 1.33. Lorrin indicates SE for APBC with t/d = 1.12 and slope of 47-deg should be more like 1.65. 1.33 is actually less than even 1/cos(47). Hmm...that seems rather odd even for APBC.

[Mobius]

Tests vs M-47.

Armor:

Glacis - 102mm@60deg, 210 BHN or LOS=204mm

 

88mm PaK43 firing AP and HVAP

 

M39 (PzGr.39?) AP penetrates glacis @ 250m

[With my standarized data I use 22cm @ 0° for my 88/71 penetration at 250m. (rounded to the nearest cm).]

 

100mm D-10TG (from T-54A) firing BR-412B APBC, BK-5 and BK-5M HEAT

 

BR-412B AP penetrates glacis @ 750m.

[i use 16cm @ 0° for my 100mm penetration at 750m.]

 

The comparison would be 22/16 or 1.375:1

 

However if Bojan can supply Yugoslav data on the 100mm D-10TG penetration we can use that to generate a comparison point and compare it with:

 

88mm M43 PaK43

M39 AP: 240mm @100m, 225 @ 500m, 200mm @1000m, 175mm @1500m, 165mm @ 2000m

glacis effective 234mm to the 88mm/L71

[jwduquette1]

The BR-271 slope effects vs. the Sherman M4A3E4's Glacis are only about 1.33.  Lorrin indicates SE for APBC with t/d = 1.12 and slope of 47-deg should be more like 1.65.  1.33 is actually less than even 1/cos(47).  Hmm...that seems rather odd even for APBC.

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Never mind. These are the limit velocity ratios between 0-degrees and 47-deg -- with t/d held constant.

 

Lorrin determines SE via t/d at 0-degrees -- but doesnt hold t/d constant as he flops over to penetration at obliquity.

 

Doing it via lorrin's method the Sherman glacis vs BR-271 AP has an SE of about 98/64 = 1.53

 

In otherwords at 900m BR-271 will do about 98mm of RHA at 0-degrees. t/d = 98mm/57mm = 1.712. At 900m BR-271 will perforate the Shermans glacis -- t/d = 64mm/57mm = 1.12

 

If I hold t/d constant -- 64mm/57mm and compare limit velocity at which BR-271 will perforate 64mm of armor at both zero degrees and 47-degrees, I get:

 

Perforation of 64mm @ 0-degrees, V(50) = 652m/s, and t/d = 1.12

Perforation of 64mm @ 47-degrees, V(50) = 872m/s (range = 900m), and t/d = 1.12

 

Slope Effect for t/d held constant at 1.12 is 872/652 = 1.33

[jwduquette1]

Anyone?... Anyone? ... Bueller?

[jwduquette1]

57mm BR271. Perforation at 0-degrees and 30-degrees as well as velocity drop is taken from its firing tables. The perforation values seem to match pretty well with the Material Svirin came up with for 57mm BR-271.

 

I've also plotted where the 47-degree perforation and 60-degree perforation results fall out in time and space. These are taken from the material Bojan posted for BR271 vs the Sherman and T34 glacis respectively.