Have used .45, .50. and .54 for deer hunting, have taken deer with all of them except my newer .50 cal barrel for the H&R. ( that's an in-line).
Seem to prefer the .50 Thompson Center Hawken, the .45 is also a T/C Hawken, the .54 is a Lyman Plains. Lighter to carry around.
Shoot mostly patch round ball, and 110 gr ff in the .50.
Reading the book (T/C) that came with the gun, gives about the same ballistics as a .30-.30.
This rifle shoots better than I do, and have split the ball on the axe blade several times at the rendezvous primitive shoots.
Actually have given away the .45 and the .54, to my daughter and son in law. respectively. (Guess that's what fathers do).
That way we can all hunt together.
Will be working on the .50 muzzle loading barrel for the H&R this fall, set up for sabots, so will have to work up a load.
Purchased this barrel when I went nuts and bought 10 different barrels for the H&R/NEF single shot Handi Rifle. Think is was about $ 85 bucks at the time, (most likely more now)