Interesting but he fails to realize that guns aren't simply "oh there is a hammer so the hammer must act as the firing pin." As for the Machine guns, there are guns that are bottom "feed", so it isn't unrealistic to have a top "feed" gun, it would probably help prevent jamming to be honest. Plus he is faced with a gun that fires like one in Destiny and dismisses it. Saying simply "nope". So yeah no use in even trying to prove to him the guns in Destiny would actually function IRL. He's just ignorant and thinks he knows everything about firearms.