I have a Mossberg 20ga Super Bantam. Took the barrel off and when I put it back on I noticed the problem. The barrel seats well in the receiver but there is a gap where is seats against the shell magazine. The gap is about 0.6mm. My question is should I tighten good and leave a gap in it, tighten extra and take the gap out, or make me a shim and put in it?
We have one of the camo super bantams and the barrel fitment is very tight. I have to use a rubber mallet to fully seat the barrel. I also use channel-lock pliers with a piece of leather to protect the paint when tightening the barrel to the magazine. I still have a very slight gap. The gap won't hurt anything so long as you are sure the barrel is fully seated.