Have a smith check the wall thickness of the barrels where the chambers were lengthened. I have a heavy barreled pin gun that someone lengthened out to 3". I have only shot 2 3/4 loads out of it but it really kills the birds. The chokes remain full and full. The barrels are still plenty thick. My main concern with shooting 3" shells out of it would be the stock. I would like to keep it in one piece