Introduction: K'nex Blow-Back Full-Auto Rifle

About: I do K'nex...a lot. It's fun to mess around with new mechanisms, and to learn about basic engineering. I build mostly guns, and love to build new concepts. I will start posting some of my 'unposted ideas' in f…

It's finally done, and here it is. This is a blow-back, fully-automatic, controllable, (the shots don't just burst out), K'nex Rifle. This is loosely based off of myOmy's controllable machine gun prototype, and credit goes to him, TheDunkis, and TheFoofinator for coming up with the concept, (they just never got to the point of building it). This gun is very fun to shoot, and I think it is the best concept gun I have ever built.
I think that this gun could be taken to a point in time that it could shoot connectors instead of rubber-bands, and that it could shoot more rounds. Right now, because of so much pressure on the lever in the back of the gun, it can only shoot two rounds. BUT, it does work. These two rounds can either be shot at the rate of a true machine gun, (not burst fire), or they can be used as semi-auto blow-back. This is where I want someone else to come in and edit the system to make it stronger, (if you want to just glue the pieces, I guess you could, but I don't like going beyond taping my pieces, (and this gun doesn't actually have any tape on it, except for the front of the gun to keep the rubber-bands for going into the cracks of the gun)). But anyway, I know that this system could be edited to be stronger and hold more rounds.
Now, right now, I only have a couple pictures and a couple videos, but I will have a full explanation of the system in this next week. So, here are some Pro's and Con's



Awesome blow-back action

Good Range for a rubber-band gun, 20-ish feet.

Looks amazing, yet performs well

Fun to mess around with

New concept

All of the system is hidden in the stock, so it doesn't look ridiculous


Only two shots can be loaded in

Rarely jams

If it breaks, (if you put too many shots in the gun), it is very time-consuming to fix.


Well, that's it for the overall view of the gun. Here are a couple videos...more will be coming. Both of these are shooting two shots.

Step 1: Internals

These are the internals of the gun without the rubber-bands you can see, the actual blow-back slide goes over the whole length of the gun, and the trigger just blocks it from being able to move forward. In the back, the slide will hit a lever, which will activate a hidden trigger, and let a rubber-band fire. When a rubber-band moves the slide forward, the top lever pushes through a hole in the bottom of the gun and lets the rubber-band fly past. When the rubber band is gone, another rubber-band pulls the slide back to load it again. The stock of the gun is really where everything happens. The reason why you can't put any more than two rubber-bands on is because they put so much stress on the hidden trigger and the lever...when the slide pushes the lever, it explodes. I don't know how to fix this unless you want to glue your pieces. Thanks for taking a look, and I hope you build it when instructions come out.


Please leave your thoughts in the comment section!


And once again, I'm gonna stress how I am running out of guns to build. Please leave some suggestions here in the comments, or on my orangeboard, (I check both on a daily basis, so I'll see them).

Step 2: Progress Since It Was Originally Made

Videos on all my progress since I first made the gun.