Caliburn 4 (C4) DIY Kit

(4 customer reviews)


Another great design by CaptainSlug! Pump-action, mag fed, high performance, rigid platform. Great for beginner nerfers or experienced nerfers alike. This is a DIY kit. Darts & magazines sold separately.

Shown as Light Blue
Shown as Black
Low (140-150 FPS)
Medium (175-200 FPS)
High (200-250 FPS) (+$10.00)
Super High (250-300FPS) (+$34.00)
FPS ranges are an estimate. Performance may vary.
Knuckle Duster (+$9.00)
Lower Stock Spacer
Custom Magwell Text (+$10.00)
Iron Sights (+$4.00)
Rail Riser (+$10.00)
Suppressor SCAR (+$15.00)
Rubber Grip Sleeve (+$10.00)
Aluminum Trigger (+$15.00)
Aluminum Sear (+$20.00)
Aluminum Rambase (+$20.00)
Plunger Black Acetal (+$21.00)
Plunger White Acetal (+$21.00)
Plunger Aluminum (+$31.00)
RMAX (+$20.00)
Stampede (+$40.00)
Angled Foregrip (+$10.00)
Pyrangle Foregrip (+$10.00)
Modular Vertical Foregrip (+$15.00)
Product total
Options total
Grand total


The Caliburn C4 is a homemade Nerf blaster originally designed by CaptainSlug. Pump action, clip-fed, variable fps. Listing is for a Caliburn C4 DIY kit. Darts, mags, and accessories sold separately. Color configurator provided by captainslug: Caliburn 4 Color Configurator

*C4 not compatible with K14 spring


  • All the parts and hardware necessary to assemble a Caliburn 4 (C4)
  • Passive Magwell Adapter
  • 1 main power spring
  • Spare screws and hardware for maintenance

Blaster Features:

  • More dry-fire safe than predecessor. Great for beginning nerfers.
  • Quick-access buttplate for easy spring swap to adjust power
  • Compatible with both half and standard (elite) dart types
  • Increased durability & rigidity from the previous versions
  • Compatible with all standard picatinny attachments and Caliburn Lower Stock Spacers
  • All Flat bar construction
  • Tool-free passive talon/nstrike mag adapter
  • Faster spring-swaps
  • Optional air-brake plunger feature
  • Maintains the takedown feature
  • Optional o-ring collet muzzle for fast barrel swaps
  • Supports elastic and extension springs for accessories
  • Higher rigidity mixed-print-orientation grip assembly
  • Still compatible with Tooth-And-Nail and other aftermarket parts



  • Darts NOT included. Darts must be purchased separately.
  • Compatible with standard nerf brand darts, as well as short darts
  • Recommended darts: Worker Gen3 Darts


  • Compatible with most standard picatinny-compatible attachment
  • Compatible with all addons featured on the listing.

What’s involved in the different power options?

*All FPS ratings are an estimate. Performance may vary.*

LOW | 140-150 FPS
Main power spring: 788
Barrel: 14″ .527

MEDIUM | 175-200 FPS
Main power spring: K25
Barrel: 14″ .527

HIGH | 200-250 FPS
Main power spring: Pro25 Plain
Barrel: 16″ .509

Main power spring: K31 + K25
Barrel: 14″ Brass/Alu Barrel

Special thanks to Captain Slug for licensing his design to us. A portion of sales goes to support Captain Slug.



Additional information

Weight 3.5 lbs
Dimensions 16 × 4 × 8 in

4 reviews for Caliburn 4 (C4) DIY Kit

  1. Helios (verified owner)

    Good part fitment and print quality, function is also good. Had some issues with correct delivery of components as ordered, but the issues have been or are in the process of being resolved reasonably and with appropriate urgency.

  2. Joseph Anderson (verified owner)

    The blaster was easy to assemble following the video they provide, which is both informative and has good humor within it, with the k31 and k25 spring combo it hits like a Mack truck, the build quality is really sturdy and I have no worries of anything breaking, it’s a very accurate blaster, and I recommend anyone looking for a tool to pick people off at a distance to get one of these, they are relatively affordable compart to other blasters coming out now days, plus they are easier and more readily available to customize than injection molded blasters. Well worth the buy!

  3. JoJo G (verified owner)

    The C4 is awesome! Finally, a blaster with the kind of power I wished for ever since I was a kid. The assembly was a fun bonding experience with my son. It was really nice because you see how everything comes together and can more readily troubleshoot any problems that come up! Also, it makes modifications easy! My son had a hard time pumping his blaster, so we replaced it with a less powerful spring! I wanted more power, so got a more powerful spring! Spring replacement is super easy! Plus, the team at Frontline Foam is responsive and extremely helpful! They want to make sure you’re completely satisfied and have great customer service! Reach out to them about anything, even if you want to just let them know how awesome the product is!

  4. Ted Kunich

    Overall a very nice blaster. My son is having a blast shooting everything and anything with this think- we had no idea that foam darts could punch a holes in cardboard boxes so easily! The kit came with all the necessary hardware and did not take too long to assemble. Overall I’m impressed with the print quality of the plastic parts – for FDM parts, there was not too much cleanup needed – a few strings here or there but no big deal. Bonus is that the STL’s for the parts are on the site, so if you have stripped a plastic part like we did during assembly, you can easily print a replacement part if you have your own 3D printer.

    The only knock I have is with the printed assembly instructions – they could use some improvement (totally neglected installing the springs for the magazine releases). Watching the assembly video from the site, they recommend using a threadlock on some of the screws during assembly – the printed instructions make no mention of this.

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