I may be mistaken, but I remember it being 5 rounds and concentrated. The 4% statistic is irrelevant since it represents all air combat, not just attacking large aircraft flying straight and level. In Vietnam the US expended 50,000 rounds of ammunition for every NVA/VC killed. That doesn't mean a rifleman had to shoot 50,000 rounds to hit someone. If you have ever watched Luftwaffe gun cam footage you can clearly see they aim for specific parts of the bomber when they get close enough. When they saddled up on a bomber they went for the gunners first, then the wings. In head-on attacks they tried to get the cockpit.