British IT 80 C Specs., other armor plate data

[Miles Krogfus]

Page 1: Title page of and BL data from the issued IT 80 C Specification document.
Page 2: Late War Properties of British Homo. and Face Hard plate used for Proof of British Shot.
Page 3: WAL report giving the chemical composition of British Homo. and Face Hard plate tested at the ABL.
Page 4: British/German armor plate hardness ranges from Pre 1937 to 1945.

[Peasant]

I have analyzed the ballistic limits given in page 1 and here is something curious I have noticed: at low T/D ratios the 2pdr AP behaves like a perfectly rigid shell but after a certain point it's behavior deviates from the trend.

[Peasant]

Another interesting thing I've noticed: the IT80C spec indicate that 80mm/0° of british RHA from 1941 should provide protection from 2pdr shot up to the striking velocity of 2450fps, but the penetration charts from 1943-1945 shown that it perforates this target already at 2390fps.
So whats the deal? I believe this is the answer:


After 1941 the specs for this gauge of british armour reduced the average BHN from 315 to 290, simple as that.