When I got my .58, I started out with the .570 roundball. But it always loaded far to hard for my tastes - and that was with a thin patch. The barrel measures out correctly. I just like a looser ball/patch combination. I have not noticed any difference in accuracy with the .562, and it loads much better for me. I HATE to have to POUND a load down the barrel from a too tight combination.
But I'm not a MOA paper-puncher. I'm a hunter and a plinker. It gives me the accuracy I need for the shooting I do. But I also only shoot 70 grains of powder for all my shooting - target/plinking/hunting. That 70 grs. does everything I need at the distances I can comfortable shoot. (Deer hunting generally stays at 50 yards or less - NEVER past 75!)
The .54 I had worked the same way. I started with a .530, but shifted to a .526. Better/easier loading with no noticable difference in my shooting. And it liked that 70 grain charge also. Ditto my .62/20 guage (using a .590 or .600).
This works for me. And, as I said, I am not interested in MOA benchrest accuracy, nor extreme long distance accuracy. This works for my type of shooting and the distances I restrict myself to. I have a hard time seeing a target at 100 yards, much less shooting at it.
Just my humble thoughts to share. Take them as such.
Mikey - yee ol' grumpy German blacksmith out in the Hinterlands
p.s. My .58 is a 30 year old generic production barrel (probably from Dixie), lathed down to octagon-to-round with wedding bands, and built into an early 1800's style Northwest Tradegun. It's one of the handiest guns I've ever owned when out hunting/plinking. And would have been just as handy if it had been a true smoothbore.
