EDIT: Just rialized the videos were private so you couldn't watch them! I made them unlisted, so you should be able to do so now!

Sorry for the long post. Many things here arn't woth reading. Just watch the videos and read some of the last paragraph, they explain it much better than words anyway.

It is possible to make the chopper shoot at you more than 1 missle per loop. The chopper is programed to reposition and shoot another missle if it was not hit by the fired-back-missle in a certain time - if it was not hit by a missle, it assumes the missle exploded. If you manage to dodge the missle long enough, the chopper would do the above, allowing you to hit it with more missles in a single loop. After the firt missle hits, the chopper will proceed the loop of shooting with missle rain and fast bullets. The best way I found is to spam the Reflex bottun and if needed, run around the area. See the video below: Yes, you can stand on a building nearby or even on the ground. Just make sure you come back to that building before he starts to shoot the bullets or he might flee from there and fail the mission.

This is a perfect example of the trick, because it also shows you how inconsistent it is. Dodging the missle long enough is pretty tricky, even with the abuse of the Reflex, and not every missle even is garanteed to actually deal damage. Still, in theory, you can redirect 6 missles in a single loop, which can save alot of time. Another huge problem is that abusing the Reflex button too can make the chopper to flee from the battlefield, causing you to fail the mission lose even more time. This is pretty rare, yet it's still a threat.

Now look at the "proper" way to do the mission: I fight the chopper as I'm expected to, and you can see that I'm faster around a minute and a half.

After comparing times, being able to hits twice in a single loop can save you up to 20 seconds (took me 40 seconds to land 2 hits in a single loop - as opposed to 54 seconds and 2 loops). That's a minute saved in the best case and it's really not worth it. Try this trick only if you attempt to redirect 6 missles at once. If not, don't bother, because it will just slow you down.

¤ The graphics are glitchy because I play on window mode (With DXWnd). There should be a way to fix that. ¤ I'm playing on the PC version with a (fake) PS3 controller, that's why the control display is numbered instead of... I don't know. It has the same layout as in console versions.