Use the cream of wheat method. Just calls for using some fast burning pistol powder such as Unique. No projectile, just a polyester filler or cotton to hold the powder in. Any would-be projectile is disentigrated upon exiting the barrel. Just be sure to clean every five fire-formings or so to clear barrel. There is also a detailed article on this at 6mmbr.com in the how-to technical articles. It's very helpful.
