Direct Impingement - How AR-15 Models Work . These two parts make the weight of the system light. The overwhelming majority of AR-15 rifles use the direct impingement system. Eugene Stoner developed direct impingement and it is the original technology used by the AR-15. Stoner selected a gas operating system to help make the AR10 (and later the AR15) lighter than the piston operated M1 Garand and M14 that preceded these rifles. Direct Impingement Pros and Cons. The Olde School from POF uses a direct impingement operating system and is packed full of function benefits that POF excels at delivering like complete ambidextrous controls, 11.5″ M-LOK compatible M-Rail, E2 extraction technology and a straight inconel® gas tube. It also has greater commonality of parts and is more accurate. The fired shell is extracted while the next round is stripped from the magazine and seated into the bolt so that the rifle can fire again. A DI, or Direct Impingement rifle, is a rifle that uses the gas from a fired cartridge to assist in the cycling of the rifle’s bolt. It refers to a traditional and common way of doing things. Direct-impingement systems force hot gas directly into the BCG and upper receiver. The classic direct impingement AR-type rifles (usually) have interchangeable parts as they follow the design on the original AR-15. Features of Direct Impingement AR 15. The uppers of Direct Impingement AR 15 rifles are lighter than that of the Gas Piston AR 15 rifle. Piston designs are generally proprietary. In traditional DI systems, as seen in the French MAS-49 and Swedish Ljungman rifles, the action is cycled by gas traveling from the barrel to the bolt carrier via a gas tube. Interestingly enough, in “the beginning” the gas gun was the new and improved. Propellant gas gets bled via a small hole in the barrel, and this gets channels via a small tube and proceeds to come directly into contact (impinge) with the bolt carrier mechanism. Direct impingement is just one way the AR-15 can use gas to cycle the bolt carrier group, and it has its own drawbacks. Generally speaking, parts are easy to come by from a variety of manufacturers. This is because of the fact that the DI systems have quite less moving parts, it includes a gas block and gas tube. Overall, in my opinion, a piston AR is a much better rifle than a direct impingement. What is Direct Impingement (DI) DI is a system that takes gas pressure from the fired round to drive the bolt carrier backwards to cycle the action. Direct Impingement. Everyone has a slightly different design, so parts are usually not interchangeable. Drawbacks of Direct-Impingement. Unfortunately, this causes a lot of carbon fouling, oil, and grime to build up inside your rifle or pistol. While the average shooter does not need the benefits of one, those who plan for SHTF would likely agree the benefits outweigh the disadvantages. Direct Impingement. The primary reason why is because a direct impingement system is cheaper than a piston system. The term Olde School dates back to the early 1800's. Direct Impingement is a method of operation that uses the expanding gasses from the fired bullet to continue the cycle of operations. Direct impingement is the original design of the AR15. Direct impingements are generally less expensive, lighter in the fore-end and most would say more accurate than their piston-driven counterparts. As the gasses travel down the barrel, they are directed through a small hole at the top of the barrel. However, a piston system is inherently cleaner because the dirty gas is vented away. Direct impingements today make up the bulk of ARs on the market, and that means there is greater parts interchangeability.