The M60A1E4 was a conceptual variant that explored using numerous remote controlled weapons, including a 20mm gun as secondary armament. A mock-up of this structure using the Type C turret was built. Equipped having a ventilated barrel shroud and ribbed artificial forearm, pistol grip, and buttstock with a flip-up shoulder https://hoytmachineguns.com/product/lot-1496-rock-island-armory-m60-machine-gun-class-iii-nfa/