When I was in the 12th Engineer Battalion, 8th Infantry Division 1970-1971 we had M-2 50 Calibers on the APCs, no M-60s, M-14s, then M-16s, M-79s, M1911A1s. In "my" day combat engineers are "officially" employed as part of the "division slice", we supported the 2nd Brigade. In combat units are generally more casual about adhering to the TO&E for small arms, thus in WWII many rifleman would "trade" their M-1 Garand for the lighter and more handier M-1 Carbine. In infantry units in the ETO 1944-45 it was found they needed twice as many automatic weapons as the "official" TO&E called for.