I fit a barrel set from a 1911 00 16ga to a 1898 Grade 1 last night. It locks on tight, on face, lever to the right. The amount of filing required was minimal and only required twenty minutes or so to achieve. But.... Because of the 13 year age difference the contour between the barrels and receiver isn't real great. The barrels measure 2.207" across the breech. The receiver is 2.174" across the balls. The difference is slight but noticeable if you look closely. The solution for a perfect fit would be to restrike the barrels at the breech which I am not going to do as the fit isn't that bad and it would slightly reduce the wall thickness at the chambers.
I dug through a pile of forends, and while several fit, and the only thing close to perfectly matching the contour of the receiver was from a hammergun so no help there.
The moral of the story: Getting it to fit is one thing, getting a fit which could pass for factory can become a little more involved. The odds of getting a good fit is more likely if they are close in age. The forend has to fit the barrels AND the receiver. So.... I'm in need of an extractor style forearm, ( iron only is OK), for a late 1800's 12 or16ga, have various forends, etc. to trade if anyone can help.