K'nex Turret Rifle: Scarlet Devil

Introduction: K'nex Turret Rifle: Scarlet Devil

About: Hey there. I won't add too much info here, as it'll show up as one big paragraph. I'm not super active anymore, on here.

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

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Step 1: 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

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

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

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

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

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    62 Discussions


    1 year ago on Step 5

    Wow. There is a sight, everything! I can’t even come close to that.

    The Knex Inventor
    The Knex Inventor

    3 years ago

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

    dr. richtofen
    dr. richtofen

    Reply 3 years ago


    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.

    The Knex Inventor
    The Knex Inventor

    Reply 3 years ago

    Bitte schön!

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

    dr. richtofen
    dr. richtofen

    Reply 3 years ago

    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.


    4 years ago

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

    dr. richtofen
    dr. richtofen

    Reply 4 years ago

    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.


    Reply 4 years ago

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


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

    dr. richtofen
    dr. richtofen

    Reply 4 years ago on Introduction

    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.



    5 years ago on Introduction

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

    dr. richtofen
    dr. richtofen

    Reply 5 years ago on Introduction

    Thanks! You as well!

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