I strongly suggest against lengthening the chambers. If you will do the necessary legwork, you can obtain low pressure loads in 2 3/4" cases/hulls that will be suitable for your gun, assuming it is really up to shooting; if it will handle 2 1/2" CIP loads, it will surely handle low pressure 2 3/4" loads. Reloading is one of the surest routes to known low pressure. Don't assume that light shot charges equal low pressure - it is not necessarily so. Many vintage shooters use one of the 7/8 oz loads of around 1150 fps at around 7000 psi in a 2 3/4" hull. The low pressure is good for the metal parts and the low recoil is good for the wood parts and for the shooter.
