The AK with a telescopic sight would be horrible as it is not that accurate, however the G3 could be used and is actually used by the Germans in a DMR role for ISAF.
That is an extremely outdated helicopter and it is also very lightly armored it could be brought down by small arms by aiming for the glass cockpit, a better alternative could be the Z9 as it can mount Anti-tank missiles , Anti-ship missiles, and torpedoes along with maybe door mounted guns or...