Sounds like you may be looking for one of the old Live Pigeon Hammer Trap Guns. Most had longer chambers and were sturdily built and almost always stand re-proof for nitro. Not for sale but I have a 30 inch Damascus nitro 2 3/4" chambered hammer trap gun with half pistol grip by W.J.Jeffery. They are out there. Half the fun is in the hunt so good luck. Leave enough over for some flowers for the wife.

A sleeved gun would be cheaper and almost certainly nitro proofed for modern ammo. Lagopus.....