Don't know how you'd ring a barrel near the muzzle.
I'm guessing that a very low load, or powder contaminated with grease or moisture, failed to push the ball out. The next shot slammed the ball into the stuck one and -- ringed barrel!
Or, the previous owner had a holster that didn't have a bottom. He sat down on a bank and unwittingly pushed the barrel down into the mud. The next time he fired it -- ringed barrel!
For this reason, holsters with end plugs sewn in them are best for field use -- a little tidbit there.
As for shortening the barrel, that's certainly an option. However, if you like the balance and looks as is, you can have the gunsmith remove the barrel, chuck it into a lathe, and back-bore from the muzzle, removing all rifling. Then he'd smooth up the interior and put a crown inside.
Removing the rifling for an inch or so back from the muzzle would make it appear to be .50 caliber or so. Made large enough, it won't interfere with the projectile as it exits the rifling.
But really, for what it would cost to do that, you could probably just get a new barrel from Dixie gun Works or Gun Parts Corporation and have it installed. Pietta may sell barrels as parts too.
I certainly wouldn't junk it out. Shortening the barrel might be the best path. The decision is yours.