Montgo-9 9mm

3d printed montgo 9 9mm

Montgo-9 9mm STL Files

Montgo-9 3D Printed Lower Receiver

Montgo-9 9mm Details

The Montgo-9 9mm is a complete upper receiver designed for use with AR-15 and AR-9 lower receivers.

3D gun developer YZY (xYeezySZN) developed a lower receiver that is designed to be compatible with the Montgo-9 uppers available for purchase online.

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YZY’s Montgo-9 package was created by remixing designs from RKSpookware’s UBAR-9 and IvanTheTroll’s AR-15 UBAR receiver, with the addition of geometry from Not_SpookyGuns’ AR-9 Firebolt platform.

The package has been modified to improve its appearance and includes an extended mag release for easier use. It is compatible with RKSpookware’s UBAR-9 but has removed some unnecessary hardware that is typically required for firearms that use a buffer tube.

Montgo-9 9mm in the Wild



Montgo-9 9mm Tech Specs

The Montgo-9 is a blowback-operated weapons system that does not require a buffer (buffer tube / spring).

The Montgo-9 upper receiver is made of hard coat anodized billet aluminum, while the bolt and trunnion are machined from 4140 steel for durability. It features a threaded barrel for attaching flash hiders or suppressors.

The Montgo-9 9mm is compatible with any 9mm AR lower receiver as well as AR-15 lower receivers retrofitted with 9mm magazine adapters. This is also obviously compatible with YZY’s Montgo-9 lower receiver.

Required Parts for the Montgo-9


1 x MatadorArms Montgo-9 Upper Receiver, Gen1

2 x 98306A164 Clevis Pin, 1/4″ Diameter, 1-7/16″ Usable Length

1 x AR15 Fire Control Group

1 x Glock Mag Catch Spring

1 x Glock Mag Release

1 x M3x30mm socket head cap screw

1 x Machined Steel Ejector for the UBAR-9 from RKSpookware

2 x M3x20mm socket head cap screws – 2x M3 hex nuts

Materials Required

The Montgo-9 requires basic gunsmithing tools and a 3D printing setup.

Using a dialed-in Ender 3 with widely available PLA+ filament will get the job done.

Tools Required

  • Set of Rollpin Punches
  • 3/8”, 5/32”, and 1/4 “ drill bits with electric handheld drill
  • Gunsmith Hammer (brass and nylon)
  • M3 hex wrench
  • Sandpaper/File
  • Lubricating Oil
  • 1/4×28 thread tap with #3 (0.213″) drill bit
  • Long 3/16” Hex Key/Wrench or flathead screwdriver depending on grip screw

Suggested 3D Print Montgo-9 Settings

The slicer settings for the 3D-printed Montgo-9 are similar to the majority of setups for other 3D gun builds but optimized by YZY:

Layer Height: 0.16-0.2

Wall Line Count: 8-12

Infill: 99%, absolutely no less.

Supports: Use support blockers around the bolt catch and mag release button areas, as documented in photos on page 8


  • PLA+ (eSun, Polymerk or simular

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Dan M.
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