Theres a problem.
When you are inside a vehicle, crewing it, and you shot, the Vehicle wont stop the bullet at all. So, when you duck and you see the Side Metal plates in your face, no matter what you do, your bullets would go trough the Armor, hit the Enemy, and you can kill them.
Its a total Exploit. BUT, im not sure, i think in vanilla i used to do this on the Humvee, i managed to get some kills by shooting straight where the enemy is.
Thats why you cant kill your own Stuka with the Rear MG, you cant kill yourself with a Pz III N, etc.