Picture of (True)Semi-automatic Knex pistol.
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. : )
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Step 1: Hopper and front

Picture of 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

Picture of 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

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

Step 4: Another important piece

Picture of another important piece
this makes the piston release as you pull back the trigger

Step 5: Hopper + firing thing

Picture of 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

Picture of + 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

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

Step 8: + thing

Picture of + 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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Knex4Life232 years ago
Sorry for my lack of knowlegde but what is a Patch.
its ok...
sneature3 years ago
i cant tell what that one piece is connected to the upper tan piece does anyone know what it is
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.
lhinkle4 years ago
really awsome gun but how to fire it
oodalumps (author)  lhinkle4 years ago
Pull the rod connector back like a trigger.
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.
oodalumps (author)  X Files3 years ago
If you really want to use this gun, here is the v2. It's a lot better.
oodalumps (author)  X Files3 years ago
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.
X Files3 years ago
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.
oodalumps (author)  X Files3 years ago
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 if you want a semiauto.
X Files3 years ago
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! :-)
X Files X Files3 years ago
o ok i see. but still plz check out min new instructable. i published it literaly 2 minutes ago!
oodalumps (author)  X Files3 years ago
This is a true semi auto. You never pull a ram back, you just pull the trigger.
ultimachris4 years ago
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.
oodalumps (author)  ultimachris4 years ago
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.
What a theif!
I go on that site, Destroying noobish guns makes me feel important.
jmand3 years ago
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
Bartboy5 years ago
If this were posted today, it would be a fail. In many ways.... :(
oodalumps (author)  Bartboy5 years ago
You do realize this is a true semi-auto, don't you?
Yes, I know that. There are a few of them now, and they are better than this. This was fantastic at the time, but it shoots less that 20 feet, and is uncomfortable.
oodalumps (author)  Bartboy5 years ago
The other ones used a lot of pieces and don't shoot any farther.
They do use a lot of pieces, but they do shoot further. A lot further.
oodalumps (author)  Bartboy5 years ago
Are you talking about the pseudo semi-autos that use lots of preloaded rubberbands?
There are many variety's... And this isn't semi-auto. It's a repeater...... (I think)
oodalumps (author)  Bartboy5 years ago
My pistol is semi-auto.
This? It doesn't shoot very fast though....
oodalumps (author)  Bartboy5 years ago
It shoots every time you pull the trigger. What's not semi-auto about it?
Well it's semi auto, but isn't it a repeater?
oodalumps (author)  Bartboy5 years ago
What are you even trying to say?
Is this a repeater or semi auto?
oodalumps (author)  Bartboy5 years ago
It's a semi-auto. I think I've said that about a hundred times. Why even ask?
What is the difference? I am asking you 'cause you probably would be more helpful that google, but I guess not....
oodalumps (author)  Bartboy5 years ago
It's a gun that shoots every time you pull the trigger. You never need to pull back any pins or rubberbands to make it shoot, only the trigger.
And a repeater is...?
oodalumps (author)  Bartboy5 years ago
You pull back something then pull the trigger. Then repeat.
i never knex you wrer on ibles...
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