For this achievement you have to kill 25 players as a doorgunner of a helicopter. I made somewhere between 20 and 25 MG doorgunner kills, and I'd really like to know how to get this achievement. Why? Because both in Steam and ingame in Stats, the number of kills registered is still zero.
So I think something is wrong with this achievement, especially because in the global rankings, the "Get Some" achievement is unlocked by 0% of the players. I can't believe that nobody since release has made 25 kills as a doorgunner.

Any ideas? There are several other achievements which have 0% unlocked, so maybe something is wrong with them too?