Rusty- changing to 2F might reduce your groups considerably. 80gr. 3F must be producing 1,200fps at least, but it is a harsh 1,200fps. The slower burning 2F gives the ball a gentler start and in large bores, generaly shoots better. It usually takes an extra 20gr. to match the vel.
: As well, don't be afraid to file a rounded groove at the breech. It doesn't have to be deep, just enough to give a sight picture. The idea of something else taped there is a good one, but usually makes it shoot too high, depending on the load. The groove is legal as it doesnt' stick above the barrel's surface.
: My bro takes the barrel off, then supports it on two shot bags, gives the barrel a whack with a lead hammer to bend it slightly to make it shoot inline and to the POI he desires. He & I have been doing this for years to make smoothbores shoot straight. Be careful- don't KINK the barrel.
; The first three we did was between bending them between the box and cab of a pickup. This worked well, but wasn't as positive as the bag trick. We do this at the range, so results can be checked as it's done.
