I have never stained them. I just tru oiled them. If it is a small fix try the tru oil and if you need to add stain you can do it again. I wonder why the barrel would not fit. I know the under rib is too long on them to fit. I have heard of guys cutting the under rib. I used a file and just dressed it up until it fit then tru oiled it. Does your hammer strike the nipple right since you put the GM barrel on? Ron