How is "armor manufacturing flaws" modelled?

[kensal]

I think the answer is that the Tiger's better armour protection absorbs more of the killing power of 17pdr's shot than the Firefly's armour absorbs of the Tiger's 88's shot

[Vanir Ausf B]

Tanks do not necessarily have the same survivability after being penetrated. A good example is earlier model Shermans vs. later models with wet ammo stowage. I don't know if Fireflys had wet stowage or not.

But I think the main reason are the different properties of the rounds fired by the tanks. The Tiger fires APHE rounds with explosive filler that detonates after penetration while the Firefly uses solid shot AP. Also, larger diameter rounds tend to do more damage than smaller diameter rounds and the Tiger's main cannon is 88mm compared to 76mm for the 17 lber.

[Michael Emrys]

Also, larger diameter rounds tend to do more damage than smaller diameter rounds and the Tiger's main cannon is 88mm compared to 76mm for the 17 lber.

Further, if the Firefly is using APDS, it is a subcaliber munition of only about 57 mm diameter if memory serves.

Michael

[John Kettler]

Vanir Ausf B,

Regret to inform you the default 17 pdr antitank round was APCBC, which is AP shell, not shot. APDS was the far less frequently seen and used other antitank round.

http://en.wikipedia.org/wiki/Ordnance_QF_17_pounde

"The 17-pounder used two types of anti-tank ammunition. Armour Piercing, Capped, Ballistic Capped (APCBC) ammunition could penetrate 140 mm of armour at 457 metres and 131 mm at 914 m at a 30-degree angle. Armour-piercing discarding sabot (APDS) could penetrate 208 mm of armour at 457 m and 192 mm at 914 m at a 30-degree angle,[6][7][8] allowing it to penetrate the armour of even the German King Tiger heavy tank."

In case you think Wiki erred, here's what ammunition expert and collector Tony Williams has to say on the matter.

http://www.ww2incolor.com/forum/showthread.php/5731-The-17pounder-at-gun-The-forgotten-best-tank-killer-of-ww2!

"The 17 pdr normally used APCBC ammo, with which it penetrated 118mm/1000 yards/at 30 degrees from normal. The APDS version used a solid tungsten carbide core (I have one on my shelf) which was 57mm rather than 76mm diameter, and was fired at a much higher velocity since the entire projectile was lighter. It could penetrate 170mm/1000 yards/30 degrees."

Regards,

John Kettler

[Vanir Ausf B]

Yes, I typed shot when I should have typed shell. Thank you for the lesson in semantics, and the extraneous ballistics. The salient point I was making is that it has no explosive filler, which does not seem to be contradicted by anything you posted.

[akd]

Yes, the Brits did not use a bursting charge in their AP shell, replacing it with an inert filler, which effectively made the ammunition AP shot.

[John Kettler]

Vanir Ausf B and akd,

The Isigny firing trials appear to indicate otherwise. In U.S. usage, and it was a U.S. test, APCBC is AP shell, not shot. APCBC is derived from a naval shell.

http://www.ww2f.com/topic/22293-us-army-firing-test-of-76mm-17pdr/

"U.S. Army Firing Test No.3

U.S. Army Firing Tests conducted August 1944 by 12th U.S. Army Group at Isigny, France.

Board of Officers

APO 655

30 August 1944

SUBJECT: Final report of board of officers appointed to determine comparative effectiveness of ammunition of 76mm gun and 17pdr gun.

TO: Commanding General, Twelfth Army Group.

1. The board convened pursuant to the attached order at the firing range established by First U.S. Army near Isigny, France at 1030 hours, 19 August 1944 and conducted firing tests against the front plate of German Panther Tanks. The firing was continued, as the weather and the availability of target tanks permitted, on 20 and 21 August 1944. Because of the urgency of the test, a preliminary report, dated 21 August 1944, was submitted on 22 August 1944.

2. Ammunition

a. The characteristics of the standard ammunitions tested are shown below:

Ammunition M/V Complete

Rd. Wt. Projectile

Weight Description

76mm APC M62

(Lot# ODCM-104) 2600 24.80 15.44 Armor piercing cap, windshield, base fuze, and tracer.

76mm HVAP T4

(Lot# PA 9-1) 3400 18.90 9.50 Light weight projectile with 3.9 lb tungsten carbide core 1½" in diamter in steel sheath. Aluminium body, steel base, windshield, and tracer.

17pdr APCBC

(Lot# JIB 3/44-2301) 2900 35.50 17.00 Armor piercing cap, windshield, and tracer.

17pdr SABOT

(Lot# KBY 7/44-Lot 2) 3950 26.30 08.15 Discarding SABOT with 3.9 lb tungsten carbide core 1½" in diameter, steel base, and tracer."

Uwe Feist many years ago did a Weapons No. 1, which covered, among other things, the Firefly in depth, with extensive coverage of the gun and ammo. There were two and only two antitank ammunition types listed: APCBC and APDS. Nowhere did it say a word about plugged ammunition. To my knowledge, this wasn't done on the 17-pdr, which had excellent penetration, but it was done on our ammo supplied to the British because our cannon, especially on the short barreled Shermans, needed every possible bit of help vs the newer Panzers.

There's a definitive way to resolve this: the manual, which is available through ioffer (.usual), as follows

BRITISH 17PDR A.T.GUN AMMUNITION REGULATIONS CD NEW

Meanwhile, our own John D. Salt has helpfully compiled data from WO 219/2806. In it, the chart clearly shows APCBC for the 17 pdr.

http://mr-home.staff.shef.ac.uk/hobbies/ww2pen3.pdf

Adding to the confusion is David Honner's site. One the one hand he says APCBC is shell for the Americans and Germans, but says British APCBC is plugged, (explosive free) shot, but lists only 75mm ammo in his example.

http://amizaur.prv.pl/www.wargamer.org/GvA/background/ammotypes5.html

If someone lives near Kew, the PRO has this to offer. Regrettably, it's not online!

WO 195/9298 Description:

Ballistics Research Committee: anti-tank engagement using APCBC and APSV/DS ammunition

http://discovery.nationalarchives.gov.uk/SearchUI/details/C1989558?descriptiontype=Full&ref=WO+195/9298

Avalanche Press has a most useful piece in which it states that shot was the initial round for the 17 pdr, after which came successive varieties of AP shell.

http://www.avalanchepress.(usual)/17-Pounder.php

(Fair Use)

The 17-pounder was given a solid steel shot as its initial service round. An improved APC shell with a penetrating cap shortly replaced this. The addition of a penetrating cap allowed greater penetration against the face-hardened armor that protected almost all German armored vehicles, but it gave no benefit against homogenous armor. Soon a newer shell with a ballistic cap in addition to the penetrating cap appeared and became the service round for the rest of the war; the ballistic cap helped reduced drag on the shell and gave it much better long-range performance. When equipped with this APCBC round the 17-pounder was the by far the best anti-tank gun on the Allied side, and was able punch straight through the frontal armor of the feared Tiger.

(Fair Use)

Absent something absolutely ironclad, I think the weight of evidence, for the CMBN time frame, strongly supports the notion that APCBC for the 17 pdr was a sophisticated form of AP shell.

Regards,

John Kettler

[Vanir Ausf B]

Vanir Ausf B and akd,

The Isigny firing trials appear to indicate otherwise. In U.S. usage, and it was a U.S. test, APCBC is AP shell, not shot. APCBC is derived from a naval shell.

John, did you even read my last post? Nothing you just posted disagrees with what I said. Your argument appears to be semantic.

[Michael Emrys]

The 17-pounder was given a solid steel shot as its initial service round. An improved APC shell with a penetrating cap shortly replaced this. The addition of a penetrating cap allowed greater penetration against the face-hardened armor that protected almost all German armored vehicles, but it gave no benefit against homogenous armor. Soon a newer shell with a ballistic cap in addition to the penetrating cap appeared and became the service round for the rest of the war; the ballistic cap helped reduced drag on the shell and gave it much better long-range performance. When equipped with this APCBC round the 17-pounder was the by far the best anti-tank gun on the Allied side, and was able punch straight through the frontal armor of the feared Tiger.

I don't know, John. I only see the word 'shell' used in that paragraph once, and there is nothing to suggest that it was not just a misnomer. Nothing in that suggests even obliquely that in its evolution the 17 pdr AT round acquired a bursting charge. So until you come up with something more explicit than you have so far, I am with akd and Vanir on this.

Michael

[John Kettler]

Vanir Ausf B,

Yes, I did indeed read your last post. to me, there's far more at stake here than mere semantics, as seen in the very long discussions about AP Shot vs AP Shell performance in the Western Desert. There, at least, the reports from the field are unequivocal: AP Shell is far more lethal than AP Shot of the same caliber and requires only a 50% intrusion into the fighting compartment to be deadly against both tank and crew. Two fundamentally different kill mechanisms.

Michael Emrys,

I presented what I found, after considerable digging. As noted, dispositive information is available, but I can't get to it presently. Until then, I shall stick to my guns, er, AP shells!

All,

While we're on the Firefly, there seems to be/have been a Firefly book in development.

http://freespace.virgin.net/shermanic.firefly/#links

Regards,

John Kettler

[John Kettler]

Vanir Ausf B and akd,

This article, from the Canadian Soldiers site, flat out says that 17 pdr APCBC is shot and cites the Osprey British Antitank Artillery in support. No idea where Osprey got its information, though. No product offered at link! (Looks over shoulder for Moon)

http://www.canadiansoldiers.com/vehicles/tanks/shermantank.htm

Am to the point I don't know what to believe anymore.

Regards,

John Kettler

[John Kettler]

Skwabie,

For matters Tiger 1, Alan Hamby's site is simply outstanding. In particular, I believe the cutaways here will help you understand the relationship between the glacis plate and the driver's plate, in terms of both thickness and what's where. No product offered!

http://www.alanhamby.com/cutaway.shtml

As you can see in this series, the hull is basically a rectangular box. Why a box? A box is easy to fabricate, though this was done by two other manufacturers off site.

http://www.alanhamby.com/factory1.shtml

Regards,

John Kettler

[Amizaur]

I checked and I see I was wrong with the Tiger's "nearly horizontal" front hull plate.

It was much more thick than I remembered - it had 60mm, and it seems it was welded to the rest so it would be hard to use it as an opening to the transmission compartment.

Have no idea when I heard/read about that, I'm sorry - I should check this before writing .

[Vanir Ausf B]

Am to the point I don't know what to believe anymore.

You should believe that it had no explosive filler, which has been my point from the beginning. The penetration of the 17 prd round is not in question.