Pump Action Knex Concept


Introduction: Pump Action Knex Concept


I have no idea if there are still active knex gun builders on this site, but I first got inspiration for my knex guns on this site, so I though I'd return the favor and share my ideas too. Anyways, this is my latest knex gun. Here are some of its attributes:

- Extremely sturdy construction

- Removable Magazine

- 6.5 inch pullback

- Magazine Release

- Simple and strong mechanisms, nothing fancy

- Moderately sturdy handle

- 50-75 ft range (my best guess, the only two factors lowering the range are the ammo choice (one slot w/white rod) and the friction caused by the pin guide.)

All of these features are relatively standard, but I have not seen a pump action gun as clean looking as this one or with as long a pull distance. I kinda built this gun with the goal of making the best gun possible using tried and true mechanisms, and I think I came close. The pump was added to give it a high rate of fire, and the design was simplified to make it as reliable as possible. The removable mag was a first for me, but in theory that should be very reliable too.

In theory, this gun is everything one could hope for. However, I have not gotten it to shoot reliably due to problems with my magazine not holding the bullets firmly in place.

Also, I want to apologize for simplistic way I try to explain my gun. I'm not trying to be insulting, I just want to be clear.

Step 1: Internal/How It Works

The plunger is placed directly below the barrel to give the pumping mechanism maximum strength, and the pump itself is restrained from all movement besides the linear movement required to reset the firing pin. Also, the pump and plunger are all one connected part, which in my opinion is a big plus because not only is it stronger, but it has less ways to fail.

Step 2: Overview/Conclusion

While this is not my first gun, it is definitely my greatest creation by far. I hope somebody likes the idea and decides to improve upon it. I think the overall design has a lot of potential because 1) it uses only a few broken pieces 2) it is very strong and sturdy and could hold pretty much as many rubber bands as you can pull back (which is quite a lot given the ergonomic pump) and 3) the perfectly smooth pull of this gun along with its full sized body make it very easy to fire rapidly. However, a magazine redesign would be needed to get the gun to shoot reliably.

Thanks for reading! Please comment, I would love the feedback.



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    23 Discussions

    Sorry but I have given up on the rapid fire pump because what I did get it was preaty much the pump pulled the trigger when you pushed it back forward so I could not get it to work by just pulling the trigger. Now I am attempting a pump that works like a real one, you pull the pump and the chamber opens and pushes a bullet from the tubular mag into the chamber. I don't know if this has been done but I have been working on it for a month now

    3 replies

    I dont think it has been done before, but allowing the bullets to be loaded into the tubular mag from one direction, (the bottom), and loaded into the chamber when coming from the front of the gun, and having the pump control when they are loaded is a very challenging mech to make. And then on top of it, you need to get a pump to slide along the "tubular" mag. It would be really cool and impressive if you could accomplish such a feat. Let me know how it goes. Good Luck!

    Yea it will be challenging, I have a pretty good idea of how it's going to work. I don't want to spoil anything but I am tired of having these visions of a gun and telling everyone about it and never successfully get it to work, so I am really going to put my heart in this one. Thanks for your feedback!

    I know the feeling. I myself have started a cool concept where a pump would be used to reload a slingshot style gun. I am currently away at school so the project is on hold but its one of those things that would be really cool but has a high chance of not working out. After all, there is only so much that can be done with knex. But then again, the only reason I build knex guns is for the challenge.


    3 years ago

    From what I can tell, this is a well constructed gun-more efficient that other pump actions I've seen

    Well first off let me say it awesome and I LOVE pump action knex guns! I'm glad to see someone else is messing with them as well. I also like that you were able to incorporate a bottom removable magazine. Is it preloadable?

    4 replies

    Yes, the magazine is preloadable. The plunger latches at the bottom of the clip to allow for easy reloading. However the only way I was able to get enough pressure on the bullets I had to add some pieces to the end of the plunger and a longer rubber band. So now the clip has this ugly rod sticking out of the bottom of it.

    Oh okay so its preloadable but you have to secure the mag pusher before loading. I was really curious because your internals are surprisingly similar to my Zip3 model (the major difference being the chambering mechanism). I use the chambering mechanism to allow preloadable magazines because the round is pushed out of the magazine, between the rods that push back the ram rod, and up into the firing chamber.
    Overall good job! I still really like how it turned out. ( I just tend to rant sometimes....)

    I saw your zip3 after I made this gun. I was also surprised at the similarities. I cant wait for you to post it so i can see how you got the mag to line up with the bolt that pushes the bullet into the chamber. Im actually trying to build a gun similar to that. Maybe mine will have 2 barrels if possible, Idk.

    As an aside, I actually sat down several times to take this gun apart and make another, but each time I caught myself admiring it and didnt have the heart to destroy it. I decided i better have a really good idea to replace this gun.

    Yeah that's kinda how I feel about Zip3. I like it a lot, and I can't really see something replacing it but that's why I make instructions....and the next Zip in the series. =P

    Cool I was working on a pump action knex gun this week that you could hold the trigger down and pump it and wont fire until you shuck it back forward so u could rapid fire without having to let go of the trigger like the Ithaca model 37 but it failed miserably.

    7 replies

    Really?! Got any old pics of the mechanism you used? I've been looking for a concept for Zip4 and that one sounds very interesting!

    Actually I don't I might can try and make a better one because the one I developed, slipped a lot and let the foreign pin go before the pump was pushed forward but I will give it another try. What are your ideas for zip 4

    Well... I don't have Zip3 published yet so all Zip4 is right now is ideas... I kind of accomplished the whole reason I built zip to begin with in Zip3 so for Zip4 I've been scrapping the bottom for ideas. So far I'm thinking Zip4 maybe: pump action slingshot, shotgun, pump action turret gun (like knex slayer maybe), and now I also like that idea you had as well. So yeah, lots of ideas involving pump action, no decisions yet. Any interesting to you?

    Dude, a pump action slingshot would be awesome. I actually tried this idea a long time ago but my gun was horribly flimsy and unreliable. If you could manage to create a really long pull back with a reliable way of latching the rubber band to the end of the bullet you could get a lot of range. A turret gun would also be cool, but i could never figure out how to fit the turret above the pump while still making the gun look decent.

    The pump action slingshot idea was my favorite as well. So far, to my knowledge, the only person who has built one successfully was kinetic. With pump action slingshot shotgun. I would change the mechanism to be like Zip3, so a mech that chambers and pulls back the elastic, so it allows preloadable magazines. My only problem when visualizing is the how the pump pulls back the elastic while being supported by a guide or something.

    Yes, exactly. My best idea involves having 7 layers to allow for such a large sliding pump and still maintain the overall strength of the gun. I really don't like having a huge slot through the middle of the gun, so the 7th layer would be to cover up such a necessary slot. The 7th layer would be attached by putting the blue rods through the holes of the 7th layer, so no yellow rods or broken pieces are needed.

    The pump would have to contact the bands in two places, at least 2 layers apart, preferably 3 or more to give the bullet a wider space to fly through. This would be possible if the trigger was blocking the bullet or if the trigger blocked the bands directly behind the bullet. 5 layers apart would be needed if the trigger stopped the bands on either side of the bullet.

    As for the cambering mech, I think you could have a little piece that moves forward to block the bullets from going up into the "chamber" after the bullet is shot, and then is pushed back when the rubber band hits it as the band is pulled back. Once the piece is pushed all the way back, the next bullet goes up into the chamber, and the piece (and the rubber band) moves forward slightly to ready itself to block the next bullet. The band would "hook" itself into the bullet. Other wise i dont see how the band would get behind the next bullet.

    Sorry for rambling, I really like the idea and all its challenges.

    I like what you're thinking, seven layers and mech wise. I may have to start laying stuff out for a gun......maybe.