I don't get why we have to defend the helicopter, why not I don't know, remove the intelligence from the helicopter and retreat? Or take weapons from the fallen enemy and use them? I'm sure they are better than the pistol you start out with.
This game gets pretty old pretty fast after you figure out the patterns, that and the not being able to get up after pouncing on someone is pretty retarded.
So according to my calculations (keep in mind it was done while I was playing Orange Box while I was waiting to respawn) it would take a person 32.4 hours to complete the 98K firing (firing off a whole clip takes 6 seconds for me).