I haven't looked at an inline, so I'm just guessing about this.
I would imagine a in-line barrel has threads on the outside of it where it fits into the reciever?
Then there is the breech plug that screws into the back of the barrel?
If this is true, you could buy a green mountain barrel and pay a gunsmith to cut off the existing breeched area (assuming the existing threads are different than the in-lines breech plug).
He could then rethread it to match the inlines breech plug.
He would then have to turn and thread the outside of the rear of the barrel to fit the reciever.
A well fitted gunsmith should be able to do this, but it would most likely cost big bucks just for his labor. :shocking: :shocking:
As for builders of inlines, I don't think there are too many who bother because there are so many inlines on the market.
I know Richard Greensides Pecatonica River Long Rifle Supply used to provide stocks, barrels and recievers for them for people who wanted to build their own, but I dont know if he still does.
I would bet the barrels he was supplying for them were the fast twist, shallow groove types like all the rest, but if your interested in what he has, call him at 815-968-1995.