BMP-2M animation discrepancy.

Firing a AG-30 on BMP 2M(one man) of MEC in local coop(don't know if this is different for deployment ore not), assures the gunner that the explosions are created by the grenades landing at the target., but to a person standing outside the BMP or whilst sitting inside the BMP and looking outside looks and sounds as if the main 30mm canon is firing(30mm canon animation in action).

Steps to reproduce:
Get 2 crewmans , tell one to sit in the gunner sit and tell the other to stand outside the BMP and look at the targets where the BMP is firing the AG-30 and look at the BMP's canon. also try seeing the canon by sitting inside the BMP and telling the gunner to swivel the turret so the passanger can see the gun whilst firing the AG-30.

Thanks.