RE: .54 1/60" ball only??
75 yards should be about right...I'm 1 1/2 or so high at 50 and about 1 inch low at 100....
I shoot 80grs Goex FFF in my .54, but I'm hunting whitetails...When I go over that I start to burn patches unless I use an over the powder wad or wasps nesting....I have shot 120grs in mine but the barrel is 1 1/16 thick at the breach tapered to 15/16th at the muzzle...So its built pretty stout....
btw...When I made this gun (finished in 1990) I did a ton of research as I had an experience with a bear on one of our farms with my .45 flinter that I had used for years on deer....I ordered the Longhunters Society record book from NMLRA...At that time the record grizzly was killed with a .54, using 120grs (I believe it was FF)...The bear was shot at 100 yards and tbe ball went through the lungs and was found flattened on the off side just under the hide....