(True)Semi-automatic Knex Pistol.





Introduction: (True)Semi-automatic Knex Pistol.

About: Very oldschool Knex gun builder. I invented everything. Now I just go to wars.

I as tinkering around and made a semi-auto one.

Oh and.. I know it's weak, because I made it mostly for scientific design, not for performance. So feel free to take it farther and make a real shooter out of it. : )

Step 1: Hopper and Front

this is the hopper and front of the gun. like the last one, the gray connectors and blue spacers are the hopper ;and the black piece under it is there to stop bullets from falling through.

Step 2: Firing Thing

the yellow rod is what hits the bullets to make them go flying; and the chunk on the right is the handle. that red connector with the green rod on it is the trigger.

Step 3: Important Piece

this is connected to the trigger and pulls the firing piston back.
(sorry the picture is blury)

Step 4: Another Important Piece

this makes the piston release as you pull back the trigger

Step 5: Hopper + Firing Thing

connect the black rod and the orange connector to: the yellow connector and the white rod on the hopper piece respectively.

Step 6: + Trigger Piece

this is a lil hard, put the red rod into the grey pieces sticking out of the shooting thing. then lift it up a little and attatch it to the trigger. then put a small black piece between the trigger and grey pieces for stability.

Step 7: Rubber Bands

put a thick rubber band on the firing piston and a thin one on the trigger.

Step 8: + Thing

put that thing on the blue rod comming off the hopper (this view is from the top of the gun)


ok now you're done!
load 7 small green rods into the hopper and hold somwere on the back (front too if you want accuracy and a more confortable position) and pull the trigger until it shoots. make 2 and use one in each hand ;-)

sorry for the sloppy instructions and any misspellings "-_-



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    262 Discussions

    i cant tell what that one piece is connected to the upper tan piece does anyone know what it is

    1 reply

    If you are talking about the gray one, it's a 2 way connector. If you are talking about the white one, it's a white rod.

    i find that the thing that pulls back the ram needs to be pulled left like a block trigger. i've made the mod that makes the gun true, and i'll post it soon.

    If you really want to use this gun, here is the v2. It's a lot better.


    Then you built it wrong. The white rod that sticks up on the front of the trigger mech hits that piece from step 4, releasing the pin.

    actually upon building it, i've found that the ammo falls out of the bottom of the magazine. i would appreciate it if you could fix that.

    1 reply

    Sounds like you didn't put in the black Y connector. Step 1, the only part I put a box over.

    But this gun is seriously old (the 6th knex gun ever posted on instructables). It isn't all that great. Just go build the WASP on knexinnovation.net if you want a semiauto.

    its a good gun, but the name isnt very accurate. truly semi automatic is where there is no ram that needs to be pulled or pumped or bolted. i have a mech i've been keeping to myself, and i think im gonna release it now. nice gun tho! :-)

    2 replies

    o ok i see. but still plz check out min new instructable. i published it literaly 2 minutes ago!

    This is a true semi auto. You never pull a ram back, you just pull the trigger.

    A mechanical masterpiece! Simplistic yet efficient, small but sturdy, it's just a brilliant piece of work! I'm putting this mech in a rifle I'm currently working on if you don't mind. I'll give credit to you if i post it.

    4 replies

    I once put an up-scaled version of this mech into a rifle. You can use it for reference:

    genius mech. do you happy to be KnexGunTutorials or Untd103? Because hes posting instructions of that rifle on his website.

    That's actually someone else, who stole ooda's design, and is posting without permission.

    dude this really is a genius design a bit peicey though like with the 1 conecters
    and every thing needs a tune up
    but i im gonna try to incorporate this into my pistol im workin on
    semi auto will make it that much better