Several years ago I happened upon a T/C 50 caliber Hawken percussion rifle and fairly quickly discovered that it had a 1:24 twist barrel that shot REAL bullets and Maxi-Balls quite well but was hopeless with roundballs. My main interest in it was as a silhouette gun, so I ordered a Green Mountain drop-in replacement barrel with a 1:70 twist. A Lee .500 roundball mold sorted out the problem of undersized balls and it is probably more accurate than my shooting suggests. But, there is a fly in the ointment: I shoot 2F Goex and have an awful time keeping the flashhole open inside the breechblock with this new barrel. Never a problem with the original barrel and no problems with a 54 caliber Renegade that also shoots 2F and roundballs. I have verified that the flashhole is the same diameter as the original barrel and there is no observable roughness. I'm stumped. Now what?