Chad: I had a 1924 20g Trojan with 2 3/8" chambers, and foolishly tried 2 3/4" 7/8 oz. skeet loads. Recoil was brutal, and if I'd been smarter would have checked the end of the shells for feathering caused by entering the forcing cones
67mm shell left - 65mm right
Please don't lengthen the chambers; end of the chamber wall thickness may be inadequate