Realistic Functional Bolter


New Member
Hey y'all, new Member first post

Recently developed an interest in WH40K and got a 3D printer and I decided for my first project I wanted to make a Realistic bolter that cycles and ejects. It was a worm that latched onto my mind so now I have to see it through. I wanted to document and share my progress here.

I enjoy firearms and have a pretty good understanding of their different interacting mechanisms, but having to actually design one is a rather enjoyable challenge
It is mildly frustrating but also funny how inconsistent and disproportional the lore is around the bolter so I've been taking a few liberties. First I designed the cartridge and built everything around that. I was inspired to kickstart this project after rewatching a video of the closed real life analogue to the Bolter, the Inzuki PAW aka the Neopup. I designed a 20 x 42mm bolter round and went from there. Why 20mm? because .75 cal is 19.05mm and I decided to round up, it sounds cooler.
After that I designed a 20 round double-stack double-feed box magazine. a 30 rounder would've been way too long, even the 20 rounder is slightly pushing it, I also have plans to make a 15 and 10 round version just to test out different proportions.
The original magazine was printed 1.5mm thick but unfortunately the stress of 20 rounds under tension caused cracking at the feed lips so I redesigned to to be 3mm.
I used the 3mm as the baseline for the build so the upper and lower receiver will be 3mm thick minimum
I then designed the mag well and lower receiver, ambidextrous mag releases, trigger, fire selector with detent pin, takedown pin etc.
The barrel had me stumped for a while, trying to get the length somewhere proportionally correct and also making it fit within my 250mm print volume so as to not misalign the rifling during assembly. Originally the barrel was 14inches plus another 2 for the chamber, I then shrunk it down to 9.8 and separated it from the chamber. Then the bolt and locking lugs became their own pain. I went with a 5 lug rotating bolt design which I hope will satisfy my vision. I worry that the feed ramp angle is too aggressive and might cause jams. Bit the round seats well in the chamber, the extractor works, and the bolt can rotate in the chamber well. So far no fitment issues.

I think the next step is to design the bolt carrier itself.

If you guys have any questions, advice, or design suggestions I'd love to hear them! I'll keep y'
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all posted
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Developed the upper receiver. Proportions are starting to settle
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Also made the brass deflector. I'm not sure if I'm fully happy with it, but that can change later
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Also made the rails for the cam pin
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Ill keep yall updated, gnight
The shape is really coming together
Added lots of holes for attachment pins and made the foregrip
I just hope its comfortable to hold and I didn't make the grooves too aggressive
The front does look a lil...empty?
There's plenty of room at the front of the receiver and in the grip for electronics and such, kinda temped to do like a light/laser in the grip, but I'm not very familiar with electronics and such
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Added sling attachment points
I'm like 95% done, just need to add connection slots for the back plate, emboss some symbols and text, and design some holes for the recoil spring
I'm going to order a spring from an airsoft store and start printing parts to test fit everything
I didnt design this around any hardware aside from 1 and 2mm pins and a small spring for the extractor and ejector. As nice as having real bolts and screws would be, I do not have the entire McMaster-Carr catalogue memorized and I didn't want to compromise the design
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The front would look rather "empty," considering there's usually winged skulls or imperial aquilas or seals on the sides of the bolters. So I guess that all depends on how 40k-ish you're planning on staying.
The front would look rather "empty," considering there's usually winged skulls or imperial aquilas or seals on the sides of the bolters. So I guess that all depends on how 40k-ish you're planning on staying.
I was referring more towards the lack of laser/flashlight/bayonet lug on the front face of the rifle. I could see an integrated flashlight/laser/targeting system installed in the foregrip, but not as a part of the upper receiver, nor do I see a practical way to attach a bayonet to this thing

As far as the Aquilas goes, I see your point. I feel like when these are issued out they are blank and then customized by the user/legion/unit. Maybe later I'll come up with something different though.
Unfortunately I've just realized that I didnt design a bolt-hold-open mechanism...I'm not sure if I want to. It's not a necessary feature but it would be nice. Damn
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I also want to emboss some technical data on the upper receiver but I'm not sure what location to put...
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Ok I know its been awhile but there is some progress
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I printed a prototype and put it together. On the plus side...IT CYCLES. THE BOLT ROTATES AND LOCKS, THE CHARGING HANDLE WORKS, THE ROUND CHAMBERS
I was so happy when I felt and heard the locking mechanism work
Unfortunately this did require some sanding and work
Lots of tolerances need to be tweaked, but on the whole it works

I didnt like how small the mag release buttons were, nor was I satisfied with the grip and trigger...
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So I redesigned the lower with a better grip shape, bigger mag release, and new trigger. I went with a 1911 style trigger since thats what a lot of the artwork leans towards. I gave it some cut outs to be different and more futuristic than the typical 3 hole cut outs but I'm not sure I'm satisfied with it.
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I also did the Dataplate engraving though, I may change the text later

Thats all for now, gnight
This waterpistol always reminded me of the WH40K bolter. The grip is thicker than one you have. Are you sure you want the top of the grip as thin as that? (This watergun has no trigger so what looks like the trigger is actually the entire grip width).
That's looking very grimdark! Do you have machined metal parts in there or are those just particularly well-done metallic paint?

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