All production pistols have 1:24 or faster twist rates and this severly limits the amount of powder you can put behind a PRB and still maintain consistent accuracy. Fast twist barrels are fine with light loads for punching paper with PRB's or very light weight conicals - If you try using heavy conicals with heavy charges, you won't have enough barrel length for the burn time and the recoil will become absolutely punishing very quickly.
.54 x 16" x 1:66