OK, I got mixed up alittle, here's a quote from the book -
"Whereas the Winchester/Remington and M14 sniper rifles began to lose accuracy over 800 yards, the specially prepared single-shot .50 caliber M2 was able to hit targets nearly 1000 yards away in darkness (the book was previously talking about night vision devises for sniper rifles), and in skillful hands, over double that distance in the daylight. Joseph Ward remembers sinking an empty sampan with an explosive bullet at a range of 2000 yards, and Carlos Hathcock killed a VC supply carrier at the extraordinary distance of 2500 yards using an M2 with an Unertl scope."
It doesn't say whether Hathcock used a semi-automatic or fully-automatic M2, but there were semi-automatic M2s... I'll take your word for it though