Patriot Ordnance Factory (POF) produces some of the highest quality AR-style rifles available on the market. POF recognized the issues caused by gas rings, gas tubes and gas keys and replaced these failure-prone components with either a short stroke gas piston or direct impingement system. Not only do these systems enhance reliability, they also drastically reduce the heat generated while firing, as well as decreasing the friction and fouling in the upper receiver assembly.