I was scratching my head during that episode. I didn't know they even made a semi-auto ma deuce. I still don't know why.
I remember reading that Carlos Hathcock used an M2 occasionally for sniping. A quick google came up with this:
"Hathcock generally used the standard sniper rifle: the Winchester Model 70 .30-06 caliber rifle with the standard 8-power Unertl scope. On some occasions, however, he used a different weapon: the .50-caliber M2 Browning Machine Gun, on which he mounted the Unertl scope, using a bracket of his own design.[9] This weapon had a Traversing and Elevating (T& E) mount that enabled precise aiming: it was accurate to 2500 yards when fired one round at a time."
link.