MERP SIG MPX Details
The 3D printed SIG MPX began its journey in early 2020 when respected developer Vinh Nguyen decided to begin development.
A quick note for those eagerly starting up their Ender 3 Printers. The SIG MPX parts kit is one of the most difficult to get your hands on.
If you have an MPX lying around, give this SIG receiver a go. Otherwise, you may need to wait until the parts kits for the MPX become more widely available.
MERP SIG MPX in the Wild
MERP SIG MPX Tech Specs
If you can 3D print a SIG MPX, you should. This 3D printed gun is a gas-
operated rotating bolt and chambered in 9mm.
There is also another route to get your SIG MPX built. 3D gun developer Vinh Nguyen notes, “yes, an EVO3/AK9 and Colt magazine remix is possible,however, I have no standing plans to incorporate them at this time.”
Required Parts for the MERP SIG MPX
A complete upper assembly should compose of the following:
- Upper receiver
- Bolt assembly
A complete lower parts kit should compose of the following:
- AR- 15 Lower Parts Kit, including:
- Trigger Bow
- Trigger Bow Spring
- Trigger Bow Guard (*MPX Specific)
- Hammer Spring
- Fire Selector
- Fire Selector Detent
- Fire Selector Detent Spring
- Fire Selector Ambidextrous Lever
- Fire Selector Spring pin
- Front Takedown Pin (*MPX/MCX specific)
- Rear Takedown Pin
- 2x Takedown Detent
- 2x Takedown Detent Spring
- Bolt- Catch
- 2x Bolt- Catch Detent
- Bolt- Catch Detent Spring
- Bolt- Catch Pin
- Magazine Release
- Magazine Release Ambidextrous Side
- Magazine Release Button (*MPX/MCX specific)
- Magazine Release Spring
- AR- 15 compatible grip of your choosing
- Bolt Buffer (*MPX/MCX specific)
- Bolt Buffer Screw (*MPX/MCX specific)
- Standard Hardware, including:
- 2x M4 Steel Hex Nut (MCC 90592A090)
- 2x M4x30 Socket Head Screw (MCC 91290A176)
Magazines and Accessories
Don’t forget you will also need the following:
- Sig Sauer MPX Magazine
You will need a standard toolset with the usual firearm-focused tools to complete the SIG MPX lower receiver:
- Gunsmithing Punch Set
- Assorted Power Bit Set
- With metric and imperial hex bits
- Metric Drill Bit Set
- 2.5mm Drill Bit
- 3 .5mm Drill Bit
- 4 .0mm Drill Bit
- 6.5mm Drill Bit
The following tools may help but are not required :
- Flathead screwdriver
Suggested 3D Print Settings
Cura or Prusa, 3D gun defaults, will work for a great finished product when printing the SIG MPX. Vinh, also provides his suggested printer settings for producing the best quality print.
Print the 3D printed Sig MPX using the above orientation. Use Cura’s “Align Face to Build Plate” tool
under “Rotate” to orient the lower receiver with the magwell facing downwards
onto the build plate.
Similarly, print the takedown standoffs with the outer-facing sides pointed
These were the printing settings used:
- Nozzle Size: 0.4mm
- Layer Height
- Height: 0.16mm
- Initial Height: 0. 16 mm
- Walls: 8
- Infill Density: 100%
- Supports: Tree Supports
- Bed Adhesion: Brim
eSUN PLA+ or PolyMaker PolyMax PLA+ is recommended for the SIG MPX lower receiver.
If you can, it is recommended to print the takedown standoffs using a nylon blend
of your choice.
MERP SIG MPX Updates
The MERP SIG MPX is in its initial public release and at version 1.0.
- v1.0: Public Release 1
- Promoted PB5 to v1.0
- v0.5: Private Beta Candidate 5
- Added assembly PDF.
- Addressed bolt-catch location issues.
- Added front takedown stand-offs.
- v0.4: Private Beta Candidate 4
- Addressed rear pin placement being so tight with the 1.85mm gap addressed
- Attempted again to fix the opening at the bottom of the gap
- Reconciled rear-pin retention geometry with the above changes.
- Return of the front takedown pin geometry to prevent detent from flying away
- v0.3: Private Beta Candidate 3
- Introduced rear-pin retention by rotating it downwards 90 degrees.
- Addressed 1.85mm gap at the back of receiver fitment.
- v0.2: Private Beta Candidate 2
- Eliminated MERP-AK9 offering (for now)
- Eliminated MERK-G9 offering (for now)
- Revised front takedown pin tolerance to better friction hold
- v0.1: Private Beta Candidate 1
- Initial commit