Introduction: K'nex Turret Rifle: Scarlet Devil

Picture of K'nex Turret Rifle: Scarlet Devil

Hello there,

After three days of tinkering around with an idea I had, the Scarlet Devil is finished.
This will be my first, and most likely only, entry to the K'nex contest, if it gets accepted.

Now, onto the gun itself:
The Scarlet Devil got its name from a title in the Touhou series of bullet hell games.
Because I don't have enough two clip connectors, I used red ones in the turret, which is the second reason to pick this name.
It combines elements from bullpup, slingshot and, of course, turret rifles.
The elements are as follows:
- Slingshot:
You load the rubberbands on a ratchet, instead of directly on the ram.
- Bullpup
The ratchet itself is located at the end of the stock, operated by two long trigger beams.
- Turret rifles
The TR-8 style turret at the front end.

Pros and Cons

+ Bullpup, thus compact
+ Eight round turret, reliable, and easy to load
+ Slingshot mechanism, you don't need to pull back all the bands you have on it at once
+ Pretty comfortable
+ You can load as many rubberbands on it as the trigger allows.

- Hooking the rubberbands on the ratchet is awkward
- Very rear-heavy
- Very low rate of fire

Step 1: Overview of the Gun

Picture of Overview of the Gun

As implied in the intro, the Scarlet Devil is kind of a crossover gun.

I chose for the bullpup, to give it an overal short length, while maintaining a decent to good pin pull distance.
The slingshot mechanism allows you to load about as many rubberbands as the trigger can take.
Another advantage this gives, is that you can all load them one by one, decreasing the strength needed to operate this weapon, when compared to a standard pin gun.
The turret maximizes reliability, ease-of-loading, and turret guns are some of the most powerfull weapons I've built in the past.

The large disadvantages of this weapon are the rate of fire, and loading the rubberbands.
Depending on how many bands you have on it, the rate of fire can become very low, as you have to hook the rubberbands on the ratchet, and then bring the pin backwards.
Because of the bullpup design, it's kind of awkward to hook the rubberbands on the hatchet, bringing the rate of fire down even more.

The standard sight I chose for this weapon is the red dot one I've used before.

Step 2: The Guts

Picture of The Guts

The Scarlet Devil uses a sliding trigger.
The trigger beams are pretty long, however, not weak at all.
They have no room to bend up or down, or inwards, as they're enclosed on these sides.
Above and underneath the beams are rows of orange connectors, preventing them from moving up or down.
In the middle, there is a row of yellow connectors, with green rods in the 45 degrees slots, blocking the beams from bending inwards.

The pin itself also has its own sort of guide.
It moves between rows of orange connectors underneath, and yellow connectors above and on the side of it.
The grey rod and red connector that holds it move between the rows of yellow connectors, keeping the rod straight.

There is a blue rod in front of the ratchet, that prevents you from pulling the pin out of the barrel behind the turret.

Step 3: Some Last Details

Picture of Some Last Details

The end of the stock is textured, so it doesn't slip off of your shoulder.
The weapon, with exception of the turret connection, is solid as a rock.

Step 4: Version 1

Picture of Version 1

The previous version of the Scarlet Devil.
This version was perhaps even sturdier than the current one, except for the fake barrel.
It had folding back sights, that worked in the same way as the one in my Peacekeeper.
The trigger hasn't changed much, as you can see. The beams on this one were entirely straight, which made them a bit stronger.
The biggest disadvantage this version had from the current one, was the height of the pin inside the gun.
The pin was located in a rather odd place, which made attaching magazines, turrets, or even a sturdy (fake) barrel difficult.

The design of Version 1 had a less compact design, but the overall length of the body was actually exactly the same.
V.2 utilizes the full length, whereas V.1 had "lost space" in the stock.

Step 5: Outro

Picture of Outro

This was the instructabe / slideshow of my Scarlet Devil.
Tell me what you think of the gun in the comments!
If you want instructions, don't be afraid to ask for them!

Since the intro

~Dr. Richtofen


The Knex Inventor (author)2016-06-10

Nice gun! Is the mechanism similar to Fred The Penguin's "Logic Bow"?


Yeah, the mechanism is somewhat similar. Both use a basic ratchet mechanism for the rubberbands, with a separate pin. Mine uses a bullpup-like set up and an enclosed rail / pin guide, which are probably the main differences.

Bitte schön!

Okay, I think I understand it. How far can it shoot?

That mostly depends on the amount of rubberbands you put on it. I only had, and still have, a bag of small rubberbands, which aren't optimal for shooting pieces. So the range I got out of it was pretty small.
But it should be able to shoot as far as, and maybe even a bit further, than a standard TR-styled gun, as you can basically load as many rubberbands as the trigger can take onto it.

Alright. Thanks!

RandomCommenter (author)2015-10-03

I have just finished building the Gen 2 HAWC bow. The ratchet system on this gun is quite similar to it, correct?

The general idea of combining a ratchet / slingshot with a turret is similar, yes. I have a slightly different trigger mechanism and a casing around the pin to prevent it from misfiring etc etc.
But, like I said, the idea behind the gun is similar.

Cool! The gen 2 HAWC bow is awesome! I favorited this gun for later possibly.

Gargamel-Knex (author)2015-05-31

WooaaaW ! Congratulations ! You are a finalist ;)


megustatrains (author)2015-06-06

damn, havent seen you make a functional gun in a while, looks like a reliable gun :D


RandomCommenter (author)2015-06-28



I haven't been able to properly test the range. But as you can load as many rubberbands on it as you'd like, it should be decent enough.


Knex2thelimit (author)2015-05-30

Congrats on being selected as a finalist!

Thanks! You as well!

CorgiCritter (author)2015-05-30

Congrats on being a finalist! This is one of my favorite projects for sure from this contest.

Thanks! You as well!

The compitition is huge this time, lots of ball machines, lots of ball macines, which are almost always impressive.

You're welcome.

the knex gun boy (author)2015-05-23

Facking vet d'r

Kona-chan (author)2015-05-10

iz noice pew

dr. richtofen (author)Kona-chan2015-05-11


Kona-chan (author)dr. richtofen2015-05-13

aber keine probleimen jah

dr. richtofen (author)Kona-chan2015-05-13

Sehr sicher Hehr Weeb

Kona-chan (author)dr. richtofen2015-05-14

Das ist gut um hüren hehr Dr. Richtofen
ich habe eine sturmgewehr liegen aber es ist blöt

dr. richtofen (author)Kona-chan2015-05-17


Kona-chan (author)dr. richtofen2015-05-19

ich haben es kepoet gemacht fur meiner tommy gun

dr. richtofen (author)Kona-chan2015-05-19


Kona-chan (author)dr. richtofen2015-05-20


fit me irl kunt

dr. richtofen (author)Kona-chan2015-05-21

no u

Great job man, how you doin' anywho? Haven't heard from you in forever? What keeps you busy these days?

I keep him busy these days B^)

dr. richtofen (author)Kona-chan2015-05-15

That was supposed to be a secret D:

Kona-chan (author)dr. richtofen2015-05-17

oh yes right shjit

dr. richtofen (author)Kona-chan2015-05-17


Kona-chan (author)dr. richtofen2015-05-20



I'm doing okay, mostly busy with practicing a couple of songs for the selection day of a study I want to start. Started playing the piano for that in March, which I've been enjoying a lot.
Other than that, just the average stuff: video games, anime and manga, music, that kind of stuff.

How're you? You were kind of "absent" until recently as well.

You are very welcome! Good to hear man! Yeah? Sounds like a blast. Yeah, same here, I keep pretty busy with, like you say, the "average stuff," I work 40 hrs. a week +, and when I'm not doing that I'm working at home, playing music, messing around on video games, watching YouTube (I watch like 2 - 3 hrs of YouTube a day, its too much, but I can't help it), and when I really have time, build with K'NEX. Got a BAL-27 that I'm working on now, but its not going like I want it to. It is a breach loading gun as of right now, but I want it to be able to shoot out of a magazine... Not gonna happen, but we'll see...

Yeah, since, like I said, I work 40 hrs. + a week I keep pretty absent on Instructables. LOL, for me its like: "New Contest? Alright, well, time to break out the K'NEX again... Yes! Another excuse!"

need help with that mag?

Ah, yeah, with 40 hours of work in a week, and that other stuff you do, it's understandable that you aren't as active anymore.

Even though the BAL-27 isn't going as well as you'd like, I'm still looking forwards to it. I've wanted to make some new replicas as well, but they didn't go that well either :/

sandroknexmaster (author)2015-05-19


dr. richtofen (author)2015-05-17

Yeah, it's good to see a wave of newer builders, along with some of the older ones posting again.

Kona-chan (author)2015-05-17

*heavy german accent*

AUG-5OM3 (author)2015-05-11

ziet er weer goed uit Doc!

Kona-chan (author)AUG-5OM32015-05-14

oh je leeft nog

dr. richtofen (author)AUG-5OM32015-05-11


OfficialKNEXGUY (author)2015-05-14



YOU. ME. ( ͡° ͜ʖ ͡°). NOW.

I'll try and get the instructions either by tomorrow, or Saturday.

OfficialKNEXGUY (author)2015-05-14

wow... you just blew my mind again dr. richtofen. GOOD JOB!


Thank you!

About This Instructable




Bio: Hey there. I won't add too much info here, as it'll show up as one big paragraph.
More by dr. richtofen:K'nex Magpul PDR instructionsLever Action Rubberband Gun - InstructionsSteyr AUG A2 instructions
Add instructable to: