Sherman Bell, in article titled "Finding Out for Myself" Part V "Long Shells in Short Chambers" (Double Gun Journal, Winter 2001) said that with loads that are sensible in a light 2 1/2 inch gun, chamber pressures were only slightly increased by using 2 3/4 inch shells. He felt there was no reason, related to safety, to lengthen an original 2 1/2 inch chambered gun to shoot 2 3/4 shells, as long as the pressure of the 2 3/4 inch load you use is the same as the pressure of a 2 1/2 inch load.
Most turn-of-the-century U.S. maker's guns had chambers slightly shorter than the shells for which they were intended; 2 5/8" for 2 3/4" 12g. I had a 20g Parker with chambers close to 2 3/8" and recoil was markedly increased with 2 3/4" target loads.
Since 2001 the availability of factory loaded 2 1/2" shells, and components (if powder can be found) has increased markedly so it is much easier to use short shells today.
Last edited by Drew Hause; 09/30/14 10:16 AM.
