Manufacture of IMR powders dates back around 200 decades when the corporate was at first Started by E.I DuPont. Obtainable for use in many reloading programs, the IMR series of powder is reliable by reloaders all around the world.IMR 4227 Powder imr 4227 in stock now would be the Magnum Pistol Powder in the IMR lineup. If imr 4227 it states Magnum,