Only cons, in my oh-so humble opinion.
I am a metallurgist who as a side-line (sort of) was Expert Witness (for the plaintiff) in a few muzzle loading lawsuits.. The first I looked at was a guy who loaded his brass-barreled Indian blunderbuss with a large blank load of black powder with newspaper rammed down on top.
The breech-plug blew out. Lord Be Praised! It missed his head. Can't say what condition his shorts may have been.
The fine breech threads were just a little bit smeared over at the tips. Don't recall whether I could screw the thing back in, but it sure was a loose fit. You follow me? That plug was such a loose fit that it blew out without damaging the threads.
This is what you can get with Indian work. Absolutely Zero understanding of what they are doing.
This back in the 1980's. Have they improved since then? Would you bet your body parts on this?
Buy a barrel from one of the American makers. Fit it to an Indian gun if that suits your fancy. Then destroy that Indian barrel so no one can get hurt by it.
By the way - it is well known amongst competent machinists/designers that one never uses fine threads when working with brass. Only coarse threads. If your barrel maker disagrees, bid him a pleasant goodbye.