My random bullpup model
It's made to be convincing, it could probably be turned into a real firearm. It's a bullpup designed to take 5.56 NATO rounds. I designed it to be somewhat ergonomic and compact. It has the front grip from...I don't even know how long that I used on my UMP. It's pretty simple, reasonably comfortable, and lets you quickly attach any front grip or bipod you can come up with. The muzzle was made from a new concept for a rounded barrel that could be used as a real K'nex barrel. This can also take a very cruddy and simple silencer attachment (which is actually just my Master Sword handle that I never wanted to disassemble). Then I added a basic rail on top that allows it to take airsoft or real rail accessories. It's not perfect, but you can get the accessories to grip into the grooves. I added a fake charging handle that is located in a decent, but not optimal position. This flows into a cheek rest of sorts that's rather close to the back of the gun so it can accommodate the charging handle pin. Your head is kinda cramped against your shoulder, but your face itself is comfortable aiming. And the front sight is detachable if you were to add a rail sight.
I'm thinking I'll probably make a new one tonight for fun. It'll be shorter to be similar in size to a PDR. However, I might (not a definite) give it exchangeable fake barrels based on this one that allows it to lock in with a single pin. Secondly, I'm going to change the front to include an integrated folding forehandle that will also be comfortable to hold folded. Or so I hope. I'm also going to move the charging handle forward and make the roof one and the same with the rail to slim it down ever so slightly. This will also move the cheek rest forward to a more accurate position like on Dr. Richy's. Finally, I hope to add some nifty features but I'm not sure at all on these. One would be a bolt lock which probably wouldn't be too hard. It'd basically be like the charging handle is a firing pin and the bolt release would be a trigger, just mounted differently on the gun. And then the harder one would be to make a magazine release near the handle like on a PDR instead of the current one I use that makes you have to "strip" the magazine. On a real gun, this would be a great feature for making reloads a lot faster.