My Knex Pistol With Sear-system Trigger




About: Holy cow, celebrating over seven years with this website. Formerly known as RocketScientist2015.
Here is my knex gun. I made it after getting bored with seeing the same old killerk ripoffs over and over again. It is single shot with a sear-system trigger. If you use the right bands, you can get it to go about 30ft.
This is my first Instructable, comments are welcome. Here's me on Youtube firing it.

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: 1

Ok, you lasted this long on another knex gun Instructable. I suggest you pat yourself on the back and have a soda/beer.
Anyway, the first thing you need to do is make all the pieces/parts.
Pics are going to do a better job of explaining. Here is an exploded view of the gun.

Step 2: 2

Ok now you've seen the all the parts and seen in the video how they work. I'll show how to build the individual parts now, starting with the barrel.

The barrel is made of 2 grey rods, 17 red pieces (45 degrees), 3 white pieces (full circle), 2 yellow pieces (half circle), 3 blue pieces (full circles that slide together), and 2 green pieces (tiny rods). The tactical mount is made of a yellow rod and 2 blue pieces. Assemble as shown in the photos. Didn't get all of that? Reread this paragraph and look at the pics. Still didn't understand what to do? Advance to nearest large drop and jump over. You're a waste of oxygen and contribute nothing to the human genome.

Step 3: 3

Alright, assuming you're not a revenging corpse or ghost, we'll work on the handle. Oh by the way, I was just kidding about committing suicide. There is a rubber band on the handle to desensitize the trigger. It's right on the green piece in the middle.

Step 4: 4

Right, now we'll make the trigger. It is designed to release the cocked plunger by pushing on it.

Step 5: 5

Ok now for the plunger. It is a good idea to put some tape where the yellow piece and red rod connect. I found that multiple stretchy rubber bands work better than one heavy band.

Step 6: 6

Now for the trigger block/ rear assembly.

Step 7: 7

Now to assemmbly. The trickiest part is the rear/trigger assembly. You can see that the blue rod on the trigger slides into the holes on the green pieces of the block. A blue spacer on either side keeps them stable.

Step 8: 8

To commplete the rear assembly, you need to connect the trigger block and handle. The trigger is to slide into the center of the handle, and be held by the rubberband.

Step 9: 9

Right, putting it all together. The handle snaps onto the barrel and the plunger slides in, and is secured by the rubberbands, which loop onto the yellow pieces. You can change their position to compensate for rubberband size.

Step 10: 10

All of those white pieces are ammmo clips. I find for maximum effectiveness, shoot either 1 blue rod, 2 white rods, or 5 green pegs. To cock, pull the plunger back and set it on the trigger block (as in video). Pull on the trigger, point the barrel and fire. Oops, my bad, point your barrel before pulling the trigger (duh). I can get about 30 ft with the blue rod, and about 15 with the green pegs. The tactical mount is perfect for a small flashlight and red dot projector.

Be the First to Share


    • Furniture Contest

      Furniture Contest
    • Reuse Contest

      Reuse Contest
    • Made with Math Contest

      Made with Math Contest

    128 Discussions


    9 years ago on Introduction

    Im having troubles getting the trigger make the ram go off its lock and it has 4 bands on it. Please help


    9 years ago on Step 7

    Instead of the beige pieces could you use blue with no hole without the little thing sticking off it


    12 years ago on Introduction

    To the knex gunners (the 13year olds who can't spell): Go do something better with your life. Your arguments are radiculous. I really don't want your help. To the knex engineers (the college grads who spell): Thanks for the help in this argument. To the anti-knex gun people (rimar 2000): Your arguments are ridiculous as well. Your never going to convince these turd brains about guns. You have many good points for disliking the "knex gun" community. I don't like them either. I was working n this Instructable for weeks, I was quite eager for my first Instructable, so I didn't time the publishing date well. I suggest you also get a life, if your entire pation is to stamp out knex guns, you have more mental issues than the VT guy.

    10 replies

    Reply 9 years ago on Introduction

    A sear system is a different type of trigger setup. the "Sear"(Part on the back of the gun)holds the firing pin back instead of just blocking it. the trigger pushes the sear down releasing the firing pin to fire the gun.

    most real guns use sear systems.


    Reply 11 years ago on Introduction

    Thanks : ) I guess you fall into an uncategorized category. Try using FireFox, it has a spell check.


    Reply 11 years ago on Introduction

    I do use firefox lol. its a glitch that i think my computer is causing. more then half the time i click on the spell check, and it sends me to the top of the Instructable. i have no idea why. but that is the reason why my spelling is still bad. btw, i also have a bad memory for the spelling of words because English is messed up.


    11 years ago on Introduction

    ges what, i never said that i was cool! because i no im not cool! i dont try to be cool! hell, i dont want to be cool!

    i have left him alone for 4 months (or near enough) now and so far i have shut up on this forum but you chatting to me has made me come back and reply (cause im polite) so leave me alone and ill leave you and other alone!

    (i talk in lower case when im angry!)

    1 reply

    11 years ago on Introduction

    I built a knex gun with sears trigger, but the trigger looks normal! and the trigger gets pullled normally.