Sharps- Forsyth's favourite was a 1/4 turn in the length of the barrels - being 24" barrels giving 96" twist rate. When you get up into the really big bores, like 16 and larger, about any twist from 60" on up(slower) will shoot just fine. With the really slow twist, you can't use enough powder to strip the ball, evwn with only 3 or 4 thou rifling. With a 60 or 66" twist, the goruves have to be .010" or deeper to hold, and the combo also has to be tight. The slower the twist, the hgiher the velocity and a thinner patch can be used.
: With a .69 (14 bore) and the 60" or 66" whatever it was (GreenRiver bl), the ball shot accurately right up to 165gr. 2F GOEX. I suppose that gave me the same velocity as 1860 rifle powder charge of 130gr. The little testing I did at 200gr. showed no loss in accuracy, so the ball/patch/velocity combination was still within the accuracy confines of the 60 or 66" twsit.
: Now, what the(66vs100\ or slower) faster twist also did for me, was to get virtually the same accuracy whether I was using a light 3 drs or heavy 6dram hunting long range.
: What I'm sying is that the .54 cal will shoot very well with a 60 or 66" twist with as much powder as your likely to shoot, and a slower twist isn't necessary. The worse scenario is to have a very slow twist with 20 thou rifling(or deeper). This requires a VERY tight combo to seal those deep grouves & almost makes use of hardened balls impossible with heavy charges. The slower the twist, the shallower the rifling can be & easier loading is the benefit, as long as the twist is far enough to stabilitze the ball(which doesn't take much). Hardened balls are necessary for dangerous or extremely dangerous game, like the big cats, cape buffalo & Elephant. Over here, I'd prefer a LARGE hardened ball for Grizzleys and Coastal Brown Bear.
: A haven't tried a 100" twist with 3 drams but would hazzard a guess that it would be less caccurate than the 66" twist with THAT load. The fine accuracy I got with heavy loads shows that I still wans't exceeding it's limits.
: THE ADVANTAGE of the slower twists is to allow shallower rifling, and thinner patches with hard balls. This is explained quite well in Forsyth's book. "The Sporting Rifle and it's Projectiles"- by Lietenant James Forsyth 1858, printed in 1860- originally). The book also has schematics on explosive ball(bullet) moulds. Pretty Cool Stuff. (PCS)
Daryl