Transportation and/or possession of a set of barrels cut below 18" could get you in a fair amount of trouble with the wrong people, BATF for one group. I am not a gunsmith so I could be hard pressed to prove that I was sleeving them and just cut the down for convenience. The last double I bought that had to be sleeved had a section cut out of both barrels about mid way down the barrels. I do not know if auction housed even will let you get that now.
I bought a double years ago some clown had cut the barrels down to 12". Ruined a fine shooter. Before I took the gun home I flattened the barrel ends and folded them over. Was told by a BATF agent several years later that he thought I was OK at that point because the gun was un-shootable but he said technically I was still in violation of the law. I replaced the barrels with an extra set I had at home. I think I threw the short barrels in the trash or sent it out with a large amount of metal recycling.
