I bought a FX Impact that has the smooth twist barrel. After I got it home, I discovered that there were a few pellets lodged in the barrel. I eventually got them out but either my efforts or the efforts of the previous owner did something to the smooth part or the rifling at the end. It will shoot a flyer or 2 then settle down for a few shots, still not one on top of another but about an 1" to 1.5" group then start flying again. This at 12 yds. Any suggestions? Thanks