When I was squaring the muzzle of this shotgun that has been pitted by smashing into something, most likely into rocks on the ground, I used a piloted counter-boring tool.
I turned the pilot bushing for it, out of brass, to the exact diameter at the muzzle. Easy-peasy, it was done, and the muzzle is now perfectly square to the bore.
But I also noticed that the .375" diameter 3/4" long bushing that I had to turn for this gets stuck further down the bore, about 1" from the muzzle, just far enough for my caliper not to reach it.
The barrel stamp says "full choke". In my books, full on 410 should be .398". What I have feels like it is extra-full by the same standard.
Should I turn the bore at the muzzle to the .398" cylinder true to the bore axis, until it tapers out toward the breach, or leave the gun the way it is?
I only ever blasted a round of trap with it, to test after buying, and it broke 20 out of 25. But now I may have to hunt with it and the proper pattern is becoming more important.