As of now, if you shoot at a helmet at point blank range with a 9mm gun, it will block bullets indefinitly and won't do any damage to the player.

My request would be that after sustained fire in the same spot, any armor would start to fail eventually, be it body armor or vehicle armor.

Also I'm not sure a military helmet is able to stop any bullet at point blank range, 9mm maybe but only at a distance ? The game states it's effective against shrapnel, not ammo.