Editing Direct impingement (section)

===Stoner bolt and carrier piston system===
[[File:M16 rifle Firing FM 23-9 Fig 2-7.png|thumb|Stoner internal piston action system]]

The original AR-10 action designed by [[Eugene Stoner]] (later developed into the [[ArmaLite AR-15]], [[M16 rifle]], and [[M4 carbine]]) is commonly called a direct impingement system, but it does not actually utilize this mechanism. In {{US Patent|2951424}}, the designer states: "This invention is a true expanding gas system instead of the conventional impinging gas system."<ref>{{cite web|url=https://patents.google.com/patent/US2951424 |title=Patent US2951424 - GAS OPERATED BOLT AND CARRIER SYSTEM |date= |access-date=2013-04-11}}</ref> Gas is routed from a port in the barrel through a gas tube, directly to a chamber inside the bolt carrier. The bolt within the bolt carrier is fitted with [[piston ring]]s to contain the gas. In effect, the bolt and carrier act as a gas piston and cylinder. The subtleties involved in ArmaLite's patent on the gas system<ref> Eugene Stoner, 1956, Gas operated bolt and carrier system, US2951424A, https://patents.google.com/patent/US2951424A/en </ref> significantly diverge from classical direct impingement; upon firing, the pressurized propellant gasses exit the barrel via the gas port and travel the length of the gas tube, but instead of simply applying the inertia necessary to cycle the weapon directly to the bolt carrier, the gas is funneled inside the bolt carrier, wherein the increase in pressure results in the bolt itself acting as a piston, forcing the bolt carrier away from the barrel face.<ref name="armalite1">{{cite web |url=http://www.armalite.com/images/Tech%20Notes%5CTech%20Note%2054,%20Gas%20vs%20Op%20Rod%20Drive,%20020815.pdf |title=ARMALITE TECHNICAL NOTE 54: DIRECT IMPINGEMENT VERSUS PISTON DRIVE |archive-url=https://wayback.archive-it.org/all/20120905024032/http://www.armalite.com/images/Tech%20Notes%5CTech%20Note%2054,%20Gas%20vs%20Op%20Rod%20Drive,%20020815.pdf |archive-date=5 September 2012|website=Armalite|date=3 July 2010}}</ref> The Stoner bolt and carrier piston system is ammunition specific since it does not have an adjustable gas port or valve to adjust the weapon to various propellant and projectile or barrel length specific pressure behavior.