Patriot Ordnance Factory (POF) is an All-American small business in Phoenix Arizona specializing in making some of the best quality AR style rifles and pistols on the market. Patriot Ordnance Factory takes credit for being the first to manufacture and sell gas piston operated weapon systems on AR type rifles in the United States. POF recognized the issues caused by gas rings, gas tubes, and gas key and replaced these failure-prone components with a short stroke gas piston or direct impingement system. Not only do these systems enhance reliability, they also drastically reduce the heat generated when firing, and decrease the friction and fouling in the upper receiver assembly.