Caliburn Mag-Fed Pump-Action Nerf Blaster

by captainslug, published

Caliburn Mag-Fed Pump-Action Nerf Blaster by captainslug Jun 11, 2017

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CHANGE NOTE 08/11/17: Strengthened upper tab of SPREADER and slightly widened the height of the slots. Added web to STOCK_ALT2. Added chamfers to RAM2 to reduce potential for fractures.

ASSEMBLY INSTRUCTIONS: http://captainslug.com/nerf/Caliburn3DPAssembly.pdf

Blaster is compatible with FULL-LENGTH and Half-length dart magazines. It is also capable of loading 1 to 4 darts at a time by simply cycling the breech more than once per priming stroke.

The Caliburn is a Mag-Fed Pump-Action Homemade Nerf Blaster design released as an Open Source Non-Commercial license file set by Captain Slug (http://www.captainslug.com).

WARNING: This blaster MAY NOT BE SAFE FOR INDOOR PLAY. Even with the weaker spring, the o-ring removed, and firing full-length darts this blaster will easily shoot faster than 150+ fps. So keep this in mind as to where and when this blaster is used. It can and will produce welts at point-blank range.

You are welcome to and encouraged to modify the files in any way you want. The Majority of the parts can be printed with infill as low as 20% in PLA, but I would recommend printing in layers of 200 Micron or smaller.

The Following parts however ARE REQUIRED to be printed at 100% infill: Bolt1, P1, P2, P3b, Ram2, Sear, Spreader, TGuard2, and TriggerAlt.

This Blaster design is also offered in a version you can machine out of polycarbonate if you are interested in crafting one from scratch. The write-up and machining templates for that version are available at: http://captainslug.com/caliburn.html

Assembled Blasters and Blaster Kits are available for sale as commissioned items.

Hardware kits to allow you to assemble on you've printed yourself are restocked nearly every weekend.

All of the above are for sale on Etsy as well as eBay.




Print Settings

Printer Brand:









300 micron


100% for some, 25% for most


None of the parts will require support material. P3b turns out ugly on some printers but will work with a little light sanding on its exterior. Some users have seen bed-warping in the sides of the Grip assembly, I'm not sure that it would really impact assembly much.


Post-Drilling of Through Holes

As covered in the instructions, all of the components of the grip MIGHT need some post-drilling of their through holes in order to fit 16ga or 1/16" weld rod pins. The need to do this depends on the accuracy of your specific printer, but I have toleranced the models to not require this step in my printer. Half of the components also include through holes for 10-32 threaded rods which will need to be checked for fit against those.

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What design software do you use?

Alibre Design 12.1. It's old, pretty crappy, and crashes a fair amount in Windows 7. Also won't work in any version of Windows newer than that. I'm stuck with it for now because it's what we use primarily at work.

If you want software that's usable go with Fusion 360. I haven't had time to learn it beyond using it to share assemblies with friends.

How big is the largest part that needs to be printed?

The largest parts are the MAG WELL (127.6 x 108.7 x 44.4 mm) and FOREGRIP (107.2 x 81 x 47.6 mm). I am able to print everything on my 152 x 152 x 158mm build area, but it takes roughly 50 hours to print everything. The RAIL_TOP is the longest piece, but will fit diagonally as provided in the STL file.

If you have a build area smaller than I do let me know if you need help getting certain parts that won't fit on your build plate.

Aug 3, 2017 - Modified 6 days ago
mjterry03 - in reply to captainslug

Thanks. The printer I am looking at getting (my first one) only has a 120 mm square build area. If I do get the printer then it won't be for another month.

Can you post a list of the parts in the hardware kit so I could buy them myself when they are out of stock?

Jul 13, 2017 - Modified Jul 13, 2017
captainslug - in reply to Temmiee

You will find that under the first "Spoiler" button on the first post of the Nerfhaven Thread.


You will end up paying $100 + shipping and will have to cut everything to length yourself. Here's a cut list you cross-check against the Hardware Kit list and the CAD Files.

Threaded rods: 14, 14, 13, 13, 13, 13, and 8 inches
Aluminum tube spacers: 11.25, 11.25, 11.25, and 6 inches
Plunger Tube: 7.375 inches
1-1/4 SCH40 Pipe for stock: 3 inches
5/8" Delrin Rod: 3.5 inches
.527" ID Barrel: 14 inches

Here is the drawing for the Bolt Arm pair.


I am selling the skirt seals through ebay for a lower shipped price than McMaster.