Hardened rather than pure lead would make ideal hard cover penetrators at that speed, Ed.
A slightly hardened 15 or 14 bore ball, small in comparrison to your 10 bore ball, driven at the low speed of 1,400fps will penetrate "Through and Through" an (Indian) elephant's head.

Solid concrete blocks are fun to shoot with hardened balls at descent speed. i reduced one to rubble with 1 shot from my 14 bore rifle. The block was 14" X 12" X 4" thick. The largest chunk was about 3" in diameter. I still have the ball as it was laying on the ground amidst the rubble.

At an initial 2,300fps, WOW!