Research Idea for Jason C

[rexford]

Jason,

The comments on the 500m penetration range for Russian 76.2mm against StuG III frontal armor got me thinking that maybe you are on to something.

Do you have access to any combat reports or firing tests where Sherman 75mm gun was matched up against the front of StuG III's with add-on frontal armor?

This is what I'am trying to sort through:

StuG III with 30mm/50mm on driver plate and nose would be compared to 75mm face-hardened penetration of 76.2mm BR-350B at 500m.

Driver plate 80mm at 11 degrees is 82mm vertical, nose 80mm at 20 degrees is about 88mm vertical.

So Russian 76.2mm APBC is not going to do too well against 30/50 if 1:1 equivalency is assumed.

However,

if we assume British firing tests against PzKPfw IIIH in Cairo, which resulted in 32mm/30mm being equal to 71mm single plate, were at 30 degrees side angle, 32/30 converts to 56mm single plate.

56/(32+30)= 90% equivalency.

So take StuG III 30/50 and convert to single plate equivalency using 90% factor and obtain 72mm single plate.

72mm at 11 degrees is about 74mm vertical

72mm at 20 degrees is about 79mm vertical

So, assuming two face-hardened plates in contact act like a single plate with 90% of the total thickness matches the Russian 76.2mm range better than assuming 115% equivalency.

Could you re-post the penetration ranges for 25 pdr AP against the front of PzKpfw III's in Africa?

With a little more work we may be able to get to the heart of this stuff and make a better assumption.

[ August 10, 2003, 08:03 PM: Message edited by: rexford ]

[Kanonier Reichmann]

Good on you Lorrin. It will be good to see you 2 working together on this thing rather than against each other.

Regards

Jim R.

[rexford]

Looking at the StuG IIIG frontal armor, there is a big difference between the add-on armor areas on PzKpfw IIIH and a StuG.

The bolted on armor plates that adorn the StuG III upper front are small in size, and the driver visor cuts out alot of the add-on plate area. Edge effects and possible absence of face-hardening around the edges would impact the StuG add-ons.

The 30mm/50mm add-on areas are also small in comparison to the 30mm at 68 degrees from vertical armor plates that make up the front upper superstructure.

When 76.2mm APBC hits 30mm face-hardened at 68 degrees from vertical, the effective resistance could be about 75mm vertical. And when that round hits the small add-on areas the resistance could be about 75mm vertical after all of the edge effects are factored in.

My inclination is that firing tests against the front of a PzKpfw IIIH would not apply to StuG III with add-on bolted plates.

I would agree with Jason C's feeling that StuG III add-on armor areas may be overrated in CMBB, but am not sure about PzKpfw IIIH and IVG/H.

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When two face-hardened plates are put together, the effective resistance should be greater than the sum of the thicknesses. Face-hardened armor works by damaging the projectile nose, which decreases the ammo's ability to make it through the softer plate area that backs the hard surface layer.

With two layered face-hardened plates, the first plate does some damage to the projectile nose and the round gets through but with reduced effectiveness against face-hard plate. After the first face-hard plate it meets another face-hard plate, so twice the damage potential.

But it is far from clear that the above theory has any validity.