The M-16A1 was derived from Colt's 5.56x45mm AR-15 and delivered to the USAF in the mid-1960s, then the US Army in Vietnam. Using pressings and plastic it was known as the "Mattel Toy" or "Mattel 16". But then the US Army issued a Maintainence Booklet in comic form (by Eisner) that was 32 pages with various Chapter titles that compared the rifle's maintainence to taking care of a young lady. One chapter stuck out- Sweet 16 and from then on the rifle was known as such (full term should be Sweet 16 Prom Queen). The VC hated the new rifle and nicknamed her "Black Death" due to 700-950 rpm at close range and the shorter 1000 mps 5.56mm round that enabled US soldiers to carry more rounds into combat. Deadly at avg range of 400m. Due to jamming and fouling problems the M-16A1 was also called "Jamming Jenny or Ginny"! First use in combat was by British forces in Borneo. Adopted by 55 nations. 20 or 30 rd box mags...