I've only found a snippet in 'The Development of RAF Bombs, 1919-1939' by Stuart Hadaway (in the Royal Air Force Historical Society Journal 45, 2009, pg.19)
The armour piercing bombs were, necessarily, thick cased. Three types were developed from 1921: 250, 500 and 2,000 lb, with, respectively, Charge:Weight Ratios of 17%, 18% and 8.8%. Naturally, these led to small explosions. The only test of any of these bombs saw one detonated below-decks on the target-ship HMS Marlborough. The damage was negligible. Also of note is that the bomb was placed there to be detonated, and not dropped.