Like as been stated worry about how safe the firearm is. I have given my father rifle with bores that look like sewer pipes an he shoots cast bullets thru them with great success. Now alot of times a bad looking bore means nothing. I would not change a all matching collectable because of a bad bore. Now a arsenal rebuild with a bad bore is really not an issue. Change the barrel. But dont be surprised that it shoots same as the old one. Alot of barrels can be made to shoot better by just counter boring them. Have saved a lot of really beat up Turkishicon an Cz Mauser rifles by doing just that.