the long range ones are around 1min mark
How do you do this? I always have trouble estimating distance with the SRAW.
only advice i can give u on that is keep ur rocket lined up with the chopper (all ur focus shouldnt be on the crosshairs) or at least try when u cant see it , so the best thing is to start with is chopper coming at u or away from u and the main thing is every time u do see a chopper try to take it down