I have an H&R 20 gauge and an H&R 357. Barrel contours are the same. That 357 is heavy. I did check and the barrels will swap out. I am wondering what other barrels might work. You used to be able to send in the action and they would fit a barrel to it. I would not mind having a 30-30. I always look when I go into a pawn shop or gun store. 45-70 would probably take a 12 gauge receiver. I like those break action single shots.