Well from my perspective and experience with a .54 TC New Englander with 70 grains of 3Fg..., it's quite accurate with that load, and that load will go thru a 120 pound whitetail at 100 yards. broadside lung shot. Never went higher than 90 grains with it, so can't say if it has accuracy problems beyond 90 grains. I did notice a slight opening of the pattern above 80 grains, and since at the time I was working on a load for a match, I stuck with the most accurate, and a fixed powder measure. So that amount was used when hunting. Of couse your particular barrel may want a different powder load, different patch combination, so you should test fire it for accuracy.
LD