The .58 and .62 come into play when you are talking elk, moose, grizzleys, etc...With whitetails, mule deer, black bears, etc a .54 gives you flatter trajectory and plenty of power...With a .54 and 80grs of FFF Goex you have a good flat shooting and hard hitting load...With a .58-.62 you have to add more powder to have a flatter trajectory and recoil builds pretty quickly...

When I decided to build my .54 back in the 80s, I did a ton of research, I bought a copy of the NMLRA record book the first year it was out...The largest grizzley taken at that time was with a .54 Hawken style rifle, 120grs of powder and a .530 patched ball...The shot was taken at 100 yards and the ball penetrated both lungs and was found under the hide on the off side, the bear ran about 50-60 yards and piled up...

I've killed around 30 deer with my .54 flinter I finished in 1990, it's all you need for whitetails...