1943, M3 (Grease gun) sub machine gun was an economical weapon design and meant to arm large quantities of american troops with large quantitles of small arms. The producer ran to 1943 to 1945 with a 30 round magazine.
1958, colt AR-15 is one of the most favored automatic rifle system in the world today. The AR-15 has proven to be a highly modular, accurate and easy to use and maintain system which has only furthered its reach the world war. And it has a 20 round magazine
1960, M18 claymore anti-personnel mine was specifically designed to kill or main enemy ground approaching a position from specific direction.
The most important gun is the Colt AR-12 because of how powerful it is and much the ammo the gun carries.