The first experimental rifle using a direct impingement system was the French ENT 1901 Rossignol B1 rifle followed by Rossignol's B2, B4 and B5. The first successful production weapon was the MAS 40 rifle adopted in March 1940. The Swedish Ag m/42 is another well-known example. Both the French and Swedish rifles use a simple system whereby the gas tube acts as a piston with a cylinder recess in the bolt carrier.
It is incorrectly believed that the AR-15/M16 rifle designed by Eugene Stoner uses a direct impingement action. In the Stoner system covered by U.S. Patent 2,951,424 Stoner specifically states that the action is not direct impingement saying ″This invention is a true expanding gas system instead of the conventional impinging gas system.″[1] Gas is routed from a port in the barrel directly to a chamber formed in the bolt carrier. The bolt acts as the piston and is sealed with small automobile-style piston rings. It is a gas piston system without an operating rod.
Found this on Wikipedia, hope this answers the DI question
It is incorrectly believed that the AR-15/M16 rifle designed by Eugene Stoner uses a direct impingement action. In the Stoner system covered by U.S. Patent 2,951,424 Stoner specifically states that the action is not direct impingement saying ″This invention is a true expanding gas system instead of the conventional impinging gas system.″[1] Gas is routed from a port in the barrel directly to a chamber formed in the bolt carrier. The bolt acts as the piston and is sealed with small automobile-style piston rings. It is a gas piston system without an operating rod.
Found this on Wikipedia, hope this answers the DI question
