I've been trying to shoot from the CH-67 Huron (with the ramp open) - that works fine - but when I tried shooting a man in the Huron (with the ramp open), bullets wouldn't go through! It seems like the game does not understand that the ramp is open and not closed. You can also see the impact of the bullet in mid-air, where the ramp is supposed to be when it is closed.

Not sure if this issue is clear, so I've taken a few screenshots.
In the first one we can see that the bullet hits an invisible ramp.
In the second one we can see a man shooting from the Huron. The bullet hits the man outside. {F25014}