Colt AR-15 Automatic Rifle

While the M16 and the AR-15 are very similar in appearance, they are quite different in function and application. Today, an AR-15 refers to the semi-automatic sporting rifle, which is only capable of firing one shot with each pull of the trigger. The term M16 refers to the selective-fire rifle used by the military.

In 1958, Eugene Stoner and Armalite developed what was to eventually become the M16 selective-fire rifle, then known simply as the AR-15 rifle. That same year, the Army tested the gun as a possible replacement for the M14.  In 1959, Armalite licensed manufacturing rights of the AR-15 to Colt.

In 1962, the Army purchased a number of AR-15 selective-fire rifles for evaluation of their potential use by troops in Vietnam. This led to a purchase of 85,000 rifles for use in combat.

It was not until 1967 that the selective-fire rifles became known as the M16 and the semi-automatic rifles became known as the AR-15, which still holds true to this day.

Between 1958 and 1966, the selective-fire rifles were known as AR-15s. The selective-fire AR-15 shown here is from that time period, which is why it does not bear today's more familiar term of M16. This example was deactivated and donated by Colt to the NRA in 1965.