Knetix Semi Auto Knex Gun




About: Sometimes it takes a man to push beyond what he thinks is possible before he realizes that possibility is a mere conception of the mind. Once that barrier is broken, the mind is no longer a hindrance, but h...

This knex gun is different from other semi auto guns because instead of using manual power to pull back the pin, the tension of wound rubber bands is used, making the trigger easier to pull and very unlikely to break when you pull it.

I give credit to extreme builder for the pullback mechanism (the black wheel)

I also give credit to revtiedye for the trigger and placement of the band wheel

Semi automatic
Very sturdy
Shoots farther than most semi auto guns (about 15 feet)

Needs to be wound every few shots
Does not shoot as far as a pull-back gun would


Step 1: Frames and Main Supports

The body frames and mandatory supports of the gun. This step also includes the safety lock

Step 2: Firing Chamber and Magazine

The firing chamber is my original design. The magazine feeds straight into it so it there's no little crevice for rods to get jammed in. This also includes the mag ram.

Step 3: Sight

The sight of the gun-sight also functions as the band guide

Step 4: The Guts

These are the innards of the gun. This includes the pullback mechanism, the band wheel, the trigger, etc.

Step 5: The Butt :)

The butt... a really easy step

Step 6: The Firing Pin

This is the firing pin that extreme builder used-i modified the tip a little to decrease friction.

Step 7: The Chain

This is the big chain that you see on the side of the gun. If you find out a way to replace the chain with gears without getting in the way of the other parts please tell me-the chain causes a lot of friction that makes it harder to pull back the pin.

Step 8: Attaching the Guts

This tells you where to put all the innards. This does not include the outer gears

Step 9: Attaching the Gears and Chain Gears

The outer gears and chain gears of the gun.

Step 10: Adding the Rubber Bands

This is where the rubber bands go

Step 11: Optional Supports

The optional supports. I would use them but you dont have to

Step 12: Winding, Loading, and Firing

You are done!!! It would be best to use a piece of surgical tubing as the wheel bands because it is stronger and thicker, so it is less likely to get jammed.



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    104 Discussions


    5 years ago on Introduction

    Why isn't "requires a bunch of broken pieces" in the cons list? It would have been nice to know that before I got nearly half-way through making it and realized I wasn't willing to break that many pieces to make this.

    Hmmm...this gun is three years old maybe? And yeah there are but they're pseudos. If you want to see an amazing semi auto check out my forum semi auto. Not sure when it will get posted though because it still needs work.


    8 years ago on Introduction

    is there an easy way to break the grey connector in step 1 pic 9?


    8 years ago on Introduction

    AMAZING!!! i love it..... im building one but it has a second ram rod (or fireing pin) that smashes in to the firing pin to pull it back after you shoot, then on your second shot you pull the same trigger but it uses a different mech.... and there you have a semi auto..... but it only shoots two times then you have to cock it (so its not true) :( but i still like it and im getting close (im just on the concept) ....... awesome gun

    1 reply

    Reply 8 years ago on Introduction

    here it is --->> still not realy working :(


    9 years ago on Step 7

    I have a method to rid yourself of the chain.  Use the little sized k'nex wheels, and a rubber band.

    1 reply

    Reply 9 years ago on Step 7

     Maybe-it might not grip well enough though. Good idea however.


    Reply 9 years ago on Introduction

    What makes you say that?  Works perfectly for me.  And if you have a problem with it you can easily mod it to fit your wants.