That's a hard question to answer. All barrels are a mystery to themselves. What shoots good in one rifle might not shoot good in another. I've never shot the big .54 caliber conicals in a fast twist barrel as I do not own one. In the .50 caliber fast twist barrels, I have shot 460 & 533 grain conicals out of them. They both did real well, but you can not put large powder charges behind them.