Decker 380 Build Kit Overview
The Decker 380 is a fully DIY .380 ACP carbine that requires no traditional firearm components. Everything—the bolt, fire control group, and magazines—is either 3D printed or assembled from hardware store materials. If you’ve been looking for an entry point into semi-automatic DIY firearms that doesn’t require tracking down regulated parts or complex machining, the Decker is it.
This complete build kit includes the barrel, firing pin assembly, springs, bolt weights, and all hardware needed to finish your Decker. Print the files, open the kit, and build. No CNC work, no press fitting, no specialized tooling beyond a basic drill and hex keys.
What Makes the Decker 380 Different
Truly DIY Semi-Automatic
Unlike designs built around AR fire control groups or Glock components, the Decker uses a completely DIY bolt and fire control group. The bolt is assembled from printed parts, threaded rod, and bolt weights included in this kit. No hunting for in-spec FCG parts, no worrying about parts kit availability. Everything you need ships in one box.
Innovative Magazine Design
The Decker’s custom magazines integrate the feed ramp directly into the magazine body rather than the receiver. This design choice simplifies the printed receiver while improving feed reliability. Magazine springs are included in the kit—print the bodies and you’re ready to load.
Configuration Flexibility
The Decker can be built as either a sideloader or toploader, and both configurations are fully ambidextrous. Choose the layout that works for your preferences and use case. The file package includes everything needed for either configuration.
Accessible Build Complexity
The Decker was designed to be one of the easiest semi-automatic firearms to build. The metalwork is limited to drilling a few holes in bar stock—work that can be done with an inexpensive drill on a workbench. Compared to builds like the FGC-9 or Shuty, the Decker dramatically reduces the machining barrier to entry.
FRT Compatibility
The DIY fire control group can be configured for semi-automatic only or semi/FRT operation. The design accommodates both trigger configurations using the same printed components with minor assembly differences.
What’s in the Decker 380 Build Kit
Core Components
The kit includes a .380 Auto barrel, firing pin tube, firing pin, guide rod, recoil spring, trigger spring, safety detent spring, and two magazine springs. These are the functional components that make your Decker run.
Assembly Hardware
Two M5x380 threaded rods and one M5x240 threaded rod form the bolt assembly backbone. Two bolt weights provide the mass needed for reliable cycling. Twenty M5x25 socket head screws handle receiver assembly. A hex key is all you need for final assembly and field stripping.
Decker 380 Build Kit FAQ
Is the Decker 380 Build Kit a complete firearm?
Where do I get the Decker 380 print files?
What printer do I need to build the Decker 380?
What tools are required to build the Decker 380?
Can I use a different barrel with the Decker 380?
What is the magazine capacity?
Is the Decker 380 legal to build?
Can I sell a Decker 380 that I build?
Legal Compliance
The Decker 380 is designed for legal home manufacture under federal law. Key compliance considerations:
Rifled Barrel: This kit includes a rifled .380 Auto barrel. Using a rifled barrel is required for legal compliance—smoothbore barrels may classify the firearm differently under the NFA.
Overall Length: The Decker is designed as a carbine platform. Ensure your completed build meets minimum overall length requirements (16″ barrel and 26″ OAL for rifle classification, or comply with pistol/SBR regulations as applicable).
State Laws Vary: Some states prohibit home-manufactured firearms, restrict magazine capacity, or have other regulations that may affect the legality of building or possessing a Decker 380. Know your local laws before ordering.
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