For me at least, fouling the bore didn't seem to have any effect. I shot different powder loads with all sorts of different bullets and only had success with the 320 great Maxi-Balls. I even tried 370 gr Maxi-Balls but never got them inside 4" at 100 yards. The 320 gr would all be within 1.5".
A lot of guys will place blame on the QLA at the end of a T/C barrel. They claim they aren't properly aligned with the barrel and causes the bullet the come out un-centered. Not sure if there's any merit to that or not. Seems like stretch since most of these can find at least something the shoots well.
