So this may be a weird question, and if I'm in the wrong subforum feel free to move it.

I've got a barrelless Carcano action sitting at the house currently that was made by Beretta, and I've had a few ideas that I never did anything with for it. A local gun shop has a barrel full of barrels that are mostly from shotguns, but there's 2 fairly new muzzleloader rifle barrels in there. They both look to be around .50 cal, but they're also cheap. Since the .50 Beowulf/12.7x42 cartridge will fit the Carcano bolt face and is a low pressure round, I'm debating turning that action into a single shot, .50 Beowulf Carcano using one of those muzzleloader barrels. Would I be asking for it to be a time bomb, or is the .50 Beowulf a sufficiently low pressure cartridge that I shouldn't have any issues using a muzzleloading .50 barrel as a blank for the conversion?

That aside, you're also looking at potential bore diameter questions marks and rate of twist that could be anywhere 1 in 24 to something like 1 in 60".

Yeah, ended up deciding against it

I though this was an interesting question. I would go ahead and take a chance on any stainless barrel. As far as pressure, I think you would have been fine. But that is just one opinion and you know what they say about opinions. The inline should be plenty fast enough twist and you can and should be hand loading for that round. it is like a million bucks a shot with factory ammo.

The Beowulf maybe a little small around the rim? I do believe some have been converted to small rim rounds. China did some 763x39 IIRC? So; that should work or easy to shove a round under the extractor and see if it fits.

Anyway, Interesting idea and question. As an owner of a Carcano with a sewer pipe bore, something to think about. I am sure I wont, but; you know -- thinking is ok.

You’re right on the stainless. Most ml barrels that aren’t stainless are made from low pressure free machining steel like 1137 (green mountain), but the stainless ml barrels I’ve seen are 416, which is the same steel used in CF barrels.