The M14 was designed in 1954 and officially became the standard-issue rifle for the U.S. Armed Forces from 1959 to 1964, with over 1 million units produced over that relatively short span of time.

If we’re going to go with length of service, then one could make the case for the M16/M4 series, which in one variant or another has been the Army’s standard issue rifle since 1965.

It is now the standard issue firearm for most units in the U.S ... A shortened variant of the M16A2 rifle, the M4 carbine provides the individual soldier operating in close quarters the ...