Sherman 75mm vs. Tiger side armor test

[Yoozername]

http://www.lonesentry.com/articles/ttt3 ... zkw-6.html

Interesting data from Lonesentry. It seems the Tigers that were captured in North Africa were shot at with Sherman M3 (75mm) guns. For whatever reason, the tests were conducted at 100 meters only. The front armor and cast mantlet on the front seemed proof. There is a chance of 'nicking-down' a AP round off the lower mantlet. Similar to the panther weakpoint. But a smaller chance.

But from 100 meters, the upper-hull side armor (80mm) could be penetrated but only up to an obliquity of 17 degrees. The lower hull side armor (60mm) was more vulnerable but an obliquity of 30 degrees could stop a 75mm AP round. I would have to assume that the round was a M72 AP.

[Mobius]

ORIGINAL: Yoozername
But from 100 meters, the upper-hull side armor (80mm) could be penetrated but only up to an obliquity of 17 degrees. The lower hull side armor (60mm) was more vulnerable but an obliquity of 30 degrees could stop a 75mm AP round. I would have to assume that the round was a M72 AP.

There is some mistake in that report as it lists the upper side and lower side both to be 62mm. The only listed armor that is 82mm is the 'turret wall'. However in the text an 'armor plate' is mentioned of 82mm (3.44").

[Yoozername]

Yes, I saw that typo. But the penetration test data reads...

The side plating shows surface hardness and brittleness, with a strong tendency to crack and flake. The side plate of the turret also flakes badly on the inside.

The limiting angle for penetration of the 75-mm gun against the 3.23 inch plate is 17°, but it will penetrate the lower 2.44 inch plate at 30°.

The guns used were the 75-mm (M.3) gun in a Sherman tank and a worn 6-pounder (Mk.III-57 mm) in a Churchill tank. It is not possible to give even an estimate of the equivalent full charge. The range for the test was restricted to 100 yards. The cast armor of the mantlet seems to be of good quality, and does not break up or crack under heavy attack. None of those examined had been penetrated. The mantlet covers the entire front of the turret and there is no doubt that it gives far better protection than an internal one.

[Mobius]

Still it's hard to pin down a number because these things are all over the place.
It's not too clear where thise comes from. It may be from WO 185/118, DDG/FV()D Armour plate experiments.

[Yoozername]

From reading the test, it would appear that British weapons were used against the Tiger and Tiger wrecks.  Note the test of a PIAT and a worn 6 pdr.  What the test does show is the effect of obliquity.  It is amazing how much protection that simple sloping of armor achieved.  Sloped armor, combined with obliquity from angled shots, gives good protection.
 
I would highly suspect that M72 ammunition or very poor quality 75mm ammunition was used.  See the link below:
 
http://www.africaaxisallied.com/blog/547101-the-sherman-introduction-in-the-desert/
 
If the US had tested against the Tiger, would they not have tested the M10 TD???  It was available at that time in North Africa.  I don't think the Brits had use of them.  Also, the bazooka was in use. 
 
Supposedly the Brits KO'd one of the first Tigers with a 6 pdr. with a side shot at 500m.  Given the description of the armor, it was probably a capped round.  I don't believe the APDS was available at the time.  Also, the restored Tiger I in the Brit museum had been KO'd by one of those lucky lower mantlet 'tick-downs' and a repair was made by the Germans before losing the tank in battle.
 
In PCO terms, I suppose the question is; How does the US 75mm M3 gun compare with the Soviet 76.2mm T34 weapon?  Also, the ammunition types.

[Mobius]

I found this in my notes. It starts out something about British tests showing:
I hate to post something where I don't know the source but I've read similar in Rexford's book.

Since Allied penetration of homogeneous armor is decreased by armor piercing caps, Tiger tank made out like a bandit. Instead of Sherman being able to penetrate Tiger front armor at close range, armor piercing caps cut penetration from about 100mm to 90mm at point blank.
75mm M72 AP solid shot can penetrate 114mm [US penetration criteria] at point blank, enough to kill Tiger via frontal hit. However, uncapped AP also loses velocity like crazy as range increases:

Homogeneous armor penetration at 0°
75mm M72 solid shot AP
109mm at 100m, 92mm at 500m, 76mm at 1000m
75mm M61 APCBC-HE
88mm at 100m, 81mm at 500m, 73mm at 1000m

75mm M72 AP may have been a better bet to combat Tiger tanks. U.S. decided that they wanted rounds with HE fillers (more casualties and damage after penetration), and they were keen on defeating face-hardened armor.

Now that site says the Cairo tests were done in March 1942. The Tigers didn't come out until the end of the year. So by then the M61 must have been the round of choice.

[Yoozername]

[left]WO 291/741 Comparison of the performance of 75mm and 76mm tank gun[/left][left]ammunition.[/left][left]The 75mm M48 is longer and heavier than the 76mm M42A1 and has greater capacity. 76mm[/left][left]M42A1 is assumed identical to the 3-inch M42A1. All three use the M48 fuze.[/left][left]Vulnerable areas against men in the open, in square feet, are given as:[/left][left]3" or 76mm M42A1 2200 sq ft[/left][left]75mm M48 2900 sq ft[/left][left]"Thickness of homogenous armour plate penetrated at 30°angle of attack by APCBC/HE shell."[/left][left]Ranges in yards.[/left][left]Range 75mm 76mm[/left][left]Point blank 79.5 108.2[/left][left]200 75.3 104.2[/left][left]400 72 100.2[/left][left]600 68.5 96.7[/left][left]800 65.5 93[/left][left]1000 63 89.7[/left][left]1200 60.3 86.3[/left][left]1400 57.8 83.1[/left][left]1600 55 80[/left][left]1800 52.6 77[/left][left]2000 50 74[/left][left]The report concludes that, whereas lack of HE performance can be compensated for by using more of[/left]the less effective shell, lack of penetrating power cannot be made up for in this way.

[Mobius]

This is how the Soviets thought the 76mm/L42.1 compared to the US 75mm using the M72 round.

[Yoozername]

The APCBC seemed to be the best overall solution as the war went on.  Rounds like the M72 just don't do well against armor striking at an angle.  Either sloped or Oblique. 
 
It is interesting that the allies used 75mmL24 AP rounds and found them superior when fired by allied 75mm guns.  I just wonder if anyone thought about using the even better 75mmL48 or even the Panther 75mmL70 APCBC projectiles modded onto a M3 75mm gun cartridge.   The 75mmL48 projectile is actually the same as the higher velocity PAK40 75mmL46 projectile.  It actually was a very tough round and would get the most from whatever velocity the sherman M3 gun would push it.

[Mad Russian]

Were rounds often modified by other than their original owners? I don't remember reading where rounds, guns or barrels were modified that much. The only exception I know of is where the Soviet guns were re-chambered for German rounds.

Good Hunting.

MR

[Yoozername]

The US certainly used German 105mm artillery ammunition during the ammunition shortage in the fall '44.  They used the German ammunition in the US Howitzers. They also used German 105mm howitzers as well (possibly with US ammunition once it was restocked).  Artillery units would have metrology tools to measure their own ammunition as well as captured ammunition.

Obviously, having the same bore size is a great starting point.  In the case of North Africa, the driving bands had to be taken down on a lathe for the German 75 AP ammunition.  The same was done for the German HE ammunition. 

The 'panther-shoot' tests where 17 pdr. and US 75mm and 76.2 mm guns were tested had some swapping of Brit and US projectiles.

But I am just conjecturing that if the early 75mmL24 AP rounds COULD be swapped, then the superior 75mmL48 and Panther 75mmL70 could have also been tried. 

There is the case of the US using captured 76.2mm ex-soviet guns from the Germans and using as indirect artillery. As far as using US 3 inch rounds, I am not sure.

edit: as far as light weapons, the Germans not only captured and used PPSh sub-mg from the Soviets, they also issues thier own ammunition for it, and ALSO retrofitted 9mm capability so that it could share MP40 ammo.

[Mobius]

PCO has the destruction number of the US 75mm/76mm APHE the same as their AP. German 75mm APHE destruction is one better.
This per the comments on the Cairo tests.

[Yoozername]

Very interesting data in that it shows performance against both homogenous and face hardened armor.  Basically it shows APC projectiles.
 
http://www.lonesentry.com/blog/armor-penetration-tables.html
 
This data comes from the July 1944 field manual FM 17-12 Tank Gunnery.  I don't believe this July version is available online.  I am very interested in securing a copy.
 
 

[Mobius]

That data in the FM is derived from TM 9 1907 manuals.
Here is a page from that manual.

I don't see M72 there.
I'ver never found a handy-dandy graph like this for the M72 or M73. I had to use a couple different tables to derive that data.

The target armor on US tests is something like 210-220 BHN hardness plate. Which is fairly soft compared to the 300 BHN German target plate.

[Yoozername]

http://www.inert-ord.net/usa03a/usa5/75mm/index.html
 
A detail of the M61
 
Most APCBC information remarks about the shattering that AP projectiles had at around 2700 fps (steel AP).  Especially against face hardened armor.  But the sherman 75mm gun could not get that near that velocity at even point blank range.  Were US AP projectiles that bad? 
 
Other documents point out that APCBC rounds were better against sloped armor.  If so, why does the US documentation that I posted, and mobius posted, not show the effects of the M61 against sloped face-hardened armor at greater than 30 degrees?  Weren't these rounds supposed to be for face hardened armor????
 
 

[Mobius]

Maybe it's because they don't make US face harden plates thinner than 2". I have a program using Nathan Okin's facehard program and ran a 75mm capped shell vs. 2" facehard armor through it. It will not penetrate 2" FH plate at 2030f/s at more than 37 degrees. So I don't see how they could do a live test.

[Yoozername]

Not sure I follow that. From this test, it seems that teh 37mm has penetrated thinner than 2 inch???

[Mobius]

That graph you presented is for 30°.

[Yoozername]

The graph shows plates thinner than 2 inches being penetrated.  I posted it in response to your conjecture:
 
Maybe it's because they don't make US face harden plates thinner than 2".
 
I don't see how the slope of the plate plays in but, yes, it's probably 30 degrees.
 
In any case, if a M61 round is so easily defeated by 50mm (2 inch) of face hardened armor at an angle of 37 degrees, then Panzer IV turret fronts (and things like the StuGIII box mantlet) would be difficult targets.  Let alone Tiger side armor. 
 
 

[Mobius]

The 75mm APC does a little better vs. US 1943 Class A FH armor. Here vs 40° armor with impact velocity of 1660 f/s (range 1500 yds) it just barely penetrates 2" armor.
(per Naval Ballistics formula)

Previously I was using post 1944 class A armor.