It was intended to replace the venerable M2 machine gun with a smaller and much lighter weapon, suitable for use inside fighting vehicles, as opposed to only on external mounts.

The weapon was developed with selectable high and low rates of fire for engagement of both ground and air targets, a feature lacking in the older M2.

It is an air-cooled, recoil operated machine gun, has a short receiver and quick change barrel, and can be configured for left or right hand feeding.

In service the M85 was found to be unreliable due to the metallic link catching in the feed system, compared to the stock M2 machine gun.

An attempt was also made to make a version of the M85 that would replace the M2 in the infantry role was designated the M85C, and features standard spade grips and can be fitted to the M3 heavy tripod.