Although the M2 .50 cal. machine gun was an excellent weapon, it is too large for many applications in armored vehicles and did not have a high enough rate of fire for use against aircraft. Following World War II, there was considerable experimentation with .50 cal. tank guns. The result was the development of the M85 .50 cal. tank machine gun. The M85 had a quick-change barrel and a dual rate of fire for use against aircraft (1000-1100 spm)or ground targets (400-500 spm). The M85 became the standard tank machine gun for a number of years. The M85C was a adapted for tripod mounting, for use, at low rate of fire, as a flexible machine gun.
The M85 .50 Caliber machine gun, which is unique to the M60 Tank and the Marine Corps AAVP7AL, has proven to be operationally unreliable and ineffective against the present generation infantry fighting vehicles (e.g., the Warsaw Pact BMP mechanized infantry combat vehicle). The Marine Corps continues to store about 3 million .50-caliber cartridges for the M85 machine gun, even though the Marine Corps has removed the M85 gun from its inventory and no other weapon system uses this type of .50-caliber ammunition.