Production of IMR powders dates back about 200 several years when the company was initially Launched by E.I DuPont. Available for use in lots of reloading apps, the IMR number of powder is dependable by reloaders all across the globe.IMR 4227 Powder in stock now would imr 4227 be the Magnum Pistol Powder during the IMR lineup. If it says Magnum, 42