Anyone ever really work with the rifled chamber inserts
for shotguns? I won a bid on a Chippa (usually yucky) X-caliber 12 ga. to .44 Magnum rifled insert about 6-7" long that uses o-rings to sort of center and retard blow-back residue. I have this Frankenstein sawed off thumper 12 and figured I could shoot .44 Specials and Magnums to add some versatility. It was cheap. I can bail on it and get my money back so no real worry.
I also have a double 20 ga. and they make 9mm and .45 ACP versions for that. It sounds like fun. A report in Firearms News had a pretty good write up on the concept for "rifled" versions by another vendor.