While working for the State of Florida as a conservator, I can remember only three gun barrels that had been shortened. One looked like a Bess barrel that had been shortened and was loaded with snipped up strips of lead for a load. It was excavated near the main gate in St. Augustine. Maybe it was used for night guard duty? The second was an R. Wilson trade gun recovered from the Apalachicola River with a 28", 20-gauge barrel. The third was French pistol recovered from a 1715 Plate Fleet wreck. The barrel had been shortened from 16" and a belt-hook/sash-hook was added. We know it was shortened because several identical pistols were recovered with 16", 20 gauge barrels. I think these 3 guns were shortened because of the needs of the owners or due to damage to the firearm. James Levy