The XM312 was a developmental lightweight heavy machine gun developed by General Dynamics in response to the U.S. military's request for a replacement of the M2 Browning, and as a complement to the XM307 ACSW grenade launcher.
The XM312 is a belt-fed weapon that is fed from either side. It features the same differential recoil system featured in the XM307.
With unit-level work and a few parts, it can be converted into an XM307 in under a few minutes. This works the other way around.
In September 2005, the U.S. military began test firing the XM312.