ARMP5 V0.13 - 3D Printable MP5 Lower for AR FCGs

ARMP5 V0.13 - 3D Printable MP5 Lower for AR FCGs Features

The ARMP5 V0.13 offers a host of innovative features that set it apart from other designs like the Unhappyarms CETME/G3 lower. Its ground-up construction based on the KF5 ensures superior ergonomics and a visually appealing finish, enhancing both form and function.

• Simplified Assembly: Unlike other lowers, this design eliminates the need for sheet metal inserts for the rear pin, using a straightforward M3 bolt and spacer for the ejector pin instead of complex bolt and nut setups.
• AR FCG Compatibility: Includes an untested version with @db-firearms:4's AR FCG reinforcement plate, potentially increasing the durability of pin holes for long-term use.
• Work-in-Progress Innovation: Future updates will include an M16 cut for @S3igu2:c's MP5-compatible FRT and a more robust ejector pinning method, showing a commitment to continuous improvement.

Note that the current ejector spacer may need replacement every few hundred rounds, a minor trade-off for an evolving beta design. Feedback is encouraged to refine this 3D-printed firearm component further.

Difficulty & Build Time

• Skill Level: Intermediate
• Estimated Build Time: 1-2 days
• Required Experience: Familiarity with 3D printing, firearm assembly, and basic hardware modifications

Hardware and Tools Required

Required Hardware

• M3 bolt and spacer for ejector pin assembly
• AR fire control group (FCG) components
• Optional: @db-firearms:4's AR FCG reinforcement plate for enhanced durability

Recommended Tools

• 3D printer with compatible materials
• Basic hand tools for assembly (screwdrivers, wrenches)
• Sanding or finishing tools for post-print cleanup
• Calipers for precise measurements during fitment

ARMP5 V0.13 - 3D Printable MP5 Lower for AR FCGs Parts

The ARMP5 V0.13 package includes STL files for the MP5 lower receiver, designed specifically for AR FCG compatibility. A version incorporating @db-firearms:4's reinforcement plate is also provided, though untested, offering an experimental option for durability-focused builders. Recommended print settings include a high infill percentage (50-70%) for structural integrity, especially around pin holes and stress points.

For materials, PETG or ABS is suggested due to their strength and heat resistance, critical for firearm components. Ensure proper bed adhesion and minimal warping during printing, as precision is key for fitment with MP5 and potential HK93 or MP5-10/40 setups. Be aware that some fitment issues, like hammer interference with HK models above 9mm, may require minor modifications as noted in the documentation.

Printer Compatibility & Settings

This design is compatible with most FDM 3D printers capable of handling durable materials like PETG or ABS. Avoid PLA due to its lower strength and heat tolerance, which are unsuitable for firearm applications. Recommended settings include a layer height of 0.2-0.3mm, 50-70% infill, and at least 3-4 wall layers for added robustness.

Ensure your printer bed is leveled and heated appropriately (around 80-100°C for ABS/PETG) to prevent warping. A brim or raft may be necessary for larger parts to improve adhesion. Post-processing, such as sanding or acetone smoothing for ABS, can enhance fit and finish for a professional result.

Conclusion

The ARMP5 V0.13 - 3D Printable MP5 Lower for AR FCGs is a promising beta release for 3D printing and firearms enthusiasts, offering a blend of innovative design and practical functionality. With its ergonomic improvements, simplified assembly, and ongoing development, it’s an exciting addition to the FOSSCAD and GUNCAD community. Download, print, and share your feedback to help shape future iterations of this cutting-edge project!