The M60A1E4 was a conceptual variant that explored the usage of various distant managed weapons, like a 20mm gun as secondary armament. A mock-up of this layout utilizing the Type C turret was manufactured. The uncomfortable wire mesh seats for the loader and gunner were being replaced with padded kinds. https://hoytmachineguns.com/product/lot-1496-rock-island-armory-m60-machine-gun-class-iii-nfa/