I have a problem with GSF members equipped with 9mm running out of ammo during our drive-bys. It also happens with Denise.
What happens is that after some minutes of shooting, they will continue to fire and it will look like their pistols are firing (muzzle flash). But they will not make sound and the target is not hit by any bullets.
So it works as if they were firing blanks that are completely silent.
I don't think this happens to the members with Desert Eagle and SMG. And I have never seen it happen unless they are under CJ's command and in a car.