One thing you can do is have the forcing cones lengthened but not the chambers. Then, should you choose to reload 2 3/4" hulls and shoot them in those short-chambered guns--which a lot of people do--the result will likely be only a fairly slight increase in pressure. A few hundred psi. At least that's what Bell discovered when he tested longer shells in shorter chambers. And the 16ga Society guys have a bunch of low pressure formulas for reloads.