Soldier Systems Daily posted that USSOCOM and USMC are looking to see who can make LWMMG(Lightweight Medium Machine Guns). It will be chambered in .338 Norma Magnum using polymer case, with interchangable barrel that has suppressor capability. The effective range is 2000m.
The hope is to have something that can shoot as far as M2, but light enough to be M240.
General Dynamics has something similar.
You can read more detail from
From: Soldier Systems Daily