FGC9 MK2 Build Kit

FGC9 MK2 Build Kit Overview

The FGC9 MK2 Build Kit gives you the hardware needed to build the most recognized 3D printed firearm in the world. The FGC9 MK2 is a 9mm pistol caliber carbine that can be built entirely from 3D printed parts and commonly available materials. This kit includes the precision components that are hardest to source: the prefabricated bolt, firing pin, rifled barrel, and all the metric hardware.

The FGC-9 (which stands for “F*** Gun Control, 9mm”) was developed as a proof of concept that functional firearms can be manufactured outside traditional supply chains. The MK2 version refined the original design with improved reliability, easier assembly, and better ergonomics. It uses a closed-bolt straight blowback action, feeds from either 3D printed magazines or OEM Glock mags, and has been successfully built and tested by thousands of people worldwide.

FGC9 MK2 Specifications

Type: Pistol caliber carbine

Caliber: 9x19mm Parabellum

Action: Closed bolt, straight blowback

Barrel Length: 4.5″ (114mm)

Overall Length: 520mm

Weight (unloaded): 2.2 kg / 4.85 lbs

Feed System: 25-round printed mag or Glock mags (up to 33 rounds)

Designers: JStark1809, IvanTheTroll, 3socksandcrocs

Not Included: Printed parts, adhesives, magnets, tools

What’s Included in the FGC9 MK2 Kit

Prefabricated Bolt Assembly
The bolt is the most critical metal component in the FGC9. This kit includes a prefabricated bolt machined from 4140 steel rod, saving you the work of cutting, welding, and heat treating your own. Also includes the firing pin machined from 3mm steel rod. These parts are ready to install.

4.5″ Rifled Barrel
A rifled 9mm barrel with proper chamber dimensions. The original FGC9 design called for ECM rifling a hydraulic tube, which works but requires significant setup and experimentation. This barrel is ready to go out of the box.

Springs
All the springs you need for the build: buffer spring (0.93″ OD, 10.5″ length), hammer spring (17mm OD, 90mm length), and smaller springs for the trigger group and other assemblies. Getting the right spring rates is critical for reliable cycling, and these are spec’d to the FGC9 MK2 requirements.

Shaft Collars
DIN 705 shaft collars in 3mm (1x) and 16mm (3x). These retain the barrel and other components in the receiver.

Metric Hardware
Complete fastener set including M3, M4, and M6 socket head screws in various lengths, hex head screws, cup point set screws, nuts, washers, and external tooth washers. All DIN standard hardware as specified in the FGC9 documentation.

Steel Rod Stock
18mm 4140 steel rod (216mm and 50mm pieces) for bolt construction if you want to build additional bolts or need backup material. Also includes 3mm low carbon steel rod (100mm) for firing pin stock.

Brass Heat-Set Inserts
Four brass threaded inserts that get melted into the printed parts with a soldering iron. These provide durable metal threads in the polymer.

5mm Hex Key
The charging handle uses a 5mm Allen key as its core. This one is sized correctly at 82.5mm overall length with a 25mm short leg.

What You Still Need for Your FGC9 MK2 Build

Printed Parts (You Print These)
The FGC9 MK2 files are available from DEFCAD,. You’ll print the upper receiver, lower receiver, pistol grip, stock assembly, charging handle components, fire control group parts, and magazine components. PLA+ at 100% infill for critical parts. The file package includes detailed print settings.

Adhesives
JB Weld or similar steel-reinforced epoxy for bonding metal to printed parts. Loctite threadlocker for fasteners. Silicone spray for lubrication.

Magnets
20x10x2mm neodymium magnets for the magazine catch system. These are common and easy to source online.

Tools
Power drill, angle grinder with cutting discs, Dremel or rotary tool, metal files, soldering iron for heat-set inserts, digital calipers, vise, and metric bit drivers. The documentation lists everything in detail.

Magazine
You can print FGC9 magazines (25 rounds) using the included files, or use OEM Glock 17 magazines with the Glock magwell adapter (33 rounds with extended mags). Both options work reliably.

Why the FGC9 MK2

The Most Documented 3D Printed Firearm
No other design has been built, tested, and refined by as many people as the FGC9. The documentation is extensive, covering everything from print settings to assembly sequences to troubleshooting. If you run into a problem, someone has already solved it and posted the fix.

Practical Performance
This isn’t a novelty or a range toy. The FGC9 MK2 is a functional 9mm carbine that runs reliably when built correctly. Closed-bolt operation means better accuracy than open-bolt designs. The carbine length gives you a stable platform with a proper stock and enough barrel for decent velocity.

Skip the Hardest Steps
The original FGC9 build requires fabricating your own bolt and rifling your own barrel. Both are achievable but require significant time, tools, and trial runs. This kit gives you a prefabricated bolt and finished barrel so you can focus on the assembly rather than metalworking.

FGC9 MK2 Build Kit FAQ