The heavier black powder loads can 'wear' on you, for sure. About any black powder load produces almost double the recoil of a smokeless load.

I noticed that with the 7 dram loads, 190gr., producing 1,550fps with the 14 bore round ball I used. The same speed could be reached easily with smokeless powder, with what felt like less than 1/2 the recoil.

That 7 dram charge was the 'heaviest' charger used in a 2 3/4" case, I believe. It is listed as the heaviest load in Greener's book.

We now know the HEAVIEST 12 bore load was 9 drams - meant for specially made heavy guns and 3" hulls. Peter, of this site, has one of those, I think - IIRC.