Too hard?
A round ball doesn't "expand". Just punches a caliber sized hole in and out.
My muzzleloader days are over, but my favorite load in my T/C Renegade .54 was a .429 caliber, 240 grain solid nose in a sabot with 90 grains of fffG.
Never had a deer run over 50 yards. There was a .429 hole entry and a .429 hole exit.
Not sure about the "why", but you could literally eat right up to the bullet hole.
A large, heavy, slow moving bullet doesn't leave much blood shot meat.
A guy I knew hunted with a .22-250. Those medium sized east Texas whitetails were blood shot from mid neck to last rib with a classic behind the leg shot.....and seldom was a shoulder salvageable!