M2 Browning Machinegun has almost an inch between where the round is loaded and where it is chambered. https://www.youtube.com/watch?v=bb4GWulXVxg Just a short GIF of the Kriss Super V and how dynamic weapon function is getting these days http://imgur.com/gallery/GpeEXny In the case of the P90 the rounds are loaded into a maggazine that parrallel with the length of the weapon. Before a round is fired, the round loaded into the weapon, turned around right-a-ways, and then chambered. http://i.imgur.com/92wYE6m.gifv The scout rifle you showed was a bullpup, not sure if you are familiar with them. Chances are, with the magazine being so close to the grip, that it is a small calibre round, probably closer to a pistol round. https://shotshowreviewsdotcom.files.wordpress.com/2012/12/iwi_us_tavor_sar_16.jpg What I am trying to get at here is not that you are wrong. The point that I am getting at is that there are people who spend their entire lives engineering things. Just because we don't don't understand something, doesn't mean that it can't exist. It just means that we're not privy to the information of how it works.