Could be that you are not aware of this excellent website:
which has the following to say about AP shells (history, 1919 - 1942):
"Used against land targets such as troops or artillery, AP shells bury themselves deep in the ground before exploding, and do not fragment like HE shells, therefore are not suitable for counter battery or anti-personnel use. Despite this, when the Japanese attacked, all the guns that could, fired on them using what HE shells they had followed by AP. The photograph shows a 9.2-Inch AP Shell fired from Fort Connaught in February 1942 on the advancing Japanese. The shell was recovered from the Pasir Panjang area. It shows how little fragmentation there could be from an AP shell."