Rock Lock, most of the guns I shoot PRB in are 1-66 or 1-48 but I have one I built myself that has a 35.5 inch barrel in 54 cal with a 1-80 twist, and of all the suprising things I have a system one with several barrels and the 50 cal barrel likes round balls its one of the best groupers @ 100 yds I use a .490 ball a ticking patch and 90 gr of Pyrodex P it was kind of a suprise I expected it would only shoot balls good with about half that much powder. Lee