once seen a bloke whom loaded his own for shows ,forward venting pistol but restricted tube ,half blanked at base and another welded in halfway up barrel to look down barrel you could not see daylight ,,he used millet (bird seed) in wax i think although it was fac and had condition on his cert he used it in wild west shows ,,dont know if your local plod will be happy for using a true fac for this type of usage