A gun I have been thinking about making a copy of was one a guy at our IPSC club was using for shotgun. He has had shoulder surgery and is rather recoil sensitive when it comes to long guns.
He took a 20 gauge Rem 1100, a special field IIRC but maybe not, had a 21" barrel I think. Add a longer mag tube, a sorbothane type uber cushy recoil pad and one of those mercury recoil tube thingies in the stock. That gun handled and recoiled way more like an M1 carbine than a riot gun. I've seen him burn down the plate rack a number of times with that gun, 6 in like 2 seconds was pretty regular.