For those of you wondering about the viability of providing sniper fire from a helicopter, I encourage you to learn more about the HITRON (Helicopter Inderdiction Tactical Squadron) of the USCG.
http://www.uscg.mil/lantarea/HITRON/index.htm
They stop drug-running go-fast boats via MH-68 Sting Ray helicopter. The helicopter, if the go-fast does not heed warning shots, paces the boat while an Aviation Gunner armed with a .50 cal rifle fires at the engines to disable it. Compared to traditional methods they are extremely successful in stopping go-fasts
