Is this a shot test

[Mike Cecil]

I believe the testing was done on the plate at the manufacturer, not once the plate was cut up into hull sections, or after it was assembled. The test was specific to ABP3 (Australian Bullet Proof No.3) plate, as this type of plate manufacture/formula was unique to Australia. As far as I can tell from the limited info I've located so far, the testing was done with a test rig and was supposed to simulate a bullet strike by service Ball ammunition, but did not actually use a ball projectile. I've been unable to find any diagrams or descriptions of the test rig, but it was built so the testing was repeatable and consistent, ie was a valid comparative measure of the brittleness and armour qualities of each ABP3 plate. You will find that all the marks - which I agree do not look anywhere like a Ball round impact at 2500-odd fps - are the same and show a flat 'punch' mark, rather than exertion of steady pressure or the impact of a pointed bullet.

ABP3 had a tendency to become very brittle if the final quenching process was done at a slightly varied temperature - early Cruiser tank hulls consistently failed the test because of the difficulties of maintaining the correct temp across such a large structure, whereas flat plate was comparatively easier to control.

ABP3 is unique to Aust armoured vehicles, so I doubt that the exact same rig with a captive pin was used in the UK or elsewhere. Certainly, it appears to be a variation on the standard test method, with pressure, speed of application etc tailored to test the qualities of ABP3, particularly brittleness.

Mike C

[David Dunlop]

Michael.

That test mark you showed was on six locations on one side of my Mk II Cdn Carrier - two, top and bottom rear, centre and front (upper front missing when this piece of plate was cut out. The other side of the carrier had the test marks in the same locations, but each location was a grouping of three marks in the pattern your middle three finger tips would make. The marks were more 'random' on the rest of the carrier - single marks or none at all.

Mike.

You are correct in that these tests were done by the plate manufacturer, prior to delivery to the vehicle maker (at least that is how it worked here in Canada with the plate made for the Carriers built by Ford). The armour plate was time-consuming to make and expensive for the day. It had to be right before going into production. A neighbour of my parents many years ago had been an engineer at the Ford Windsor plant during the war and he told me that when the pattern torch had cut back the side armour at the upper front ends, these small pieces were then used in the fabrication of the armour shrouds surrounding the fan/rad assembly, immediately aft of the front bulkhead. Waste not, want not.

David