I had a 50-90 DOUBLE BARREL built for me. 20 inch barrels. I finally got around to do some penetration testing with it. All shots were at 50 yards.

Two bales of wet hay. Two layers of rough cut (therefore true) 2 by 8 inch boards.

Loads:
525 Grain Woodleigh Round Nosed over 70.5 Grains Reloder 15
435 Grain flat nosed Performance Cast over 70 Grains Reloder 15
435 Grain flat nosed Performance Cast over 60 Grains Reloder 15

Blew through the hay and through both layers of the rough cut lumber.

I did the same test with my 54 Cal Lyman Trade muzzle loader using pure lead .530 round ball over 90 grain sof 3 F powder. The round balls got buried in the LAST 2 by 8 board.

Altogether: IMPRESSIVE.