Another reason I don't worry about shooting 2 3/4" shells in my 20 ga Fox (whatever the chamber length is) is that modern plastic hulls are much thinner than the old paper hulls. I just measured a AA, an STS, and a Federal. All miked in at about 0.017". That's not a lot of constriction, even IF the mouth doesn't fully open because of the shorter chamber. Maybe someone can measure the thickness of some new or once fired paper huls for comparison.