PLOPC gunshots are extremely loud when compared to other gunshots in the game. Please adjust the their volume to match of the one used by vanilla car.

ok Ill take a look at the car and match its sound level.

I did some testing and tried matching the sound level myself. The results indicate that the "base/sound/fight/heavy-gunshot-1.ogg" (1,2,3 and 4) played at 0.4 volume a satisfying match for the volume of other vehicles firing the machine gun. Try it for yourself and see if you agree. Cheers