Can you own a short barrel just to have it? Not attached to anything?
Until a barrel is attached to a rifle, it's just a piece of pipe. It might be a handgun barrel, it might be a shotgun barrel, it might be a rifle barrel, but until it's attached to the firearm, it's meaningless.
If I've read your question in the manner you intended, I don't think that any jurisdiction in the world limits the length of a piece of tubing, which is all a barrel is, until it's installed on the firearm.