I saw a SxS shotgun where the muzzles were beveled at the crown inside the barrel. They were just beveled inside about 1/8-1/4 of an inch. The shop says the barrels were not cut, and didn't know if it was aftermarket or factory this. Any reason why would this be done on a shotgun?

It still was choked at full/modified, and the shop owner said the pattern would still be the same.

Any insight would be appreciated.

i've never owned nor seen one like that altho i haven't had one in quite some time. no reason would have been factory. the 1st thing i'd be suspicious of is they were cut. check to see if the bbls are touching at the vertical tangency. if is a space they've almost certainly been cut back.

it could also be that somebody had bright idea of trying to make a spreader choke out of the muzzles. often, is no telling what someone has tried to do. but short answer to your question, i doubt is factory and can't imagine what anyone would hope to accomplish by doing that.

Just pulled out my Stevens 311 which I know to be unmodified and the barrels have a definite bevel at the muzzle, not 1/8 but more than 1/16. As to why, it seems as good as any way to crown a barrel, it is concentric and protected.

I have a real old stevens 5100 20 ga and it doesnt have a bevel.

Does the choke on the barrel look like it was made by compressing the out side of the tube? Maybe the bevel is just a crown cut to clean up the inside edge...