Creator: UberPoor

Open beta for my MP5 lower. Similar to the @unhappyarms:c cetme/g3 lower used in @meatbanana42069:5 's Super Safety release, however this lower was made from the ground up based on the KF5. It features better ergonomics and aesthetics (imo), on top of that it doesn't require any sheet metal inserts for the rear pin and uses a simpler M3 bolt + spacer approach to the ejector pin, rather than the bolt + square nut and washers that the Unhappyarms' lower utilizes.

This is still very much a work in progress, I have another version of the lower that will have an M16 cut for @S3igu2:c 's MP5 compatible FRT, on top of that I have ideas in the works for an even more robust and simpler method for pinning the ejector in place. As it stands now, expect to have to replace the ejector spacer every couple hundred rounds.

Included is a version that utilizes @db-firearms:4 's AR FCG reinforcement plate, which hasn't been tested yet, so I highly encourage trying it out if you're able to. I think it would greatly improve the longevity of the pin holes.

Feel free to provide feedback here, on rocket chat, or DM me on my Twitter (No, I do not mean "X", I will never call it that). Happy printing.

# MP5 and MP5K AR FCG Lower

by UberPoor

## Description

A 3D printable lower for MP5/MP5K that uses AR-15 fire control groups

## Variants

- **Pinned** - For no shelf or semi-shelf MP5's

- **FullShelf** - For MP5's that do not utilize a front pin

- **DB** - For use with DB-Firearm's FCG reinforcement plate

## Materials Required

- MP5 upper assembly

- MP5 Lower Pin(s)

- MP5 Ejector

- AR FCG (see troubleshooting for specifics)

- M5 Heat Insert

- M5x25 Screw

- M3x12 Screw (Preferably a button head screw, I like to use it in conjuction with both an M4 and M3 washer)

- AR compatible grip of your choice (grips with beaver tails mostly work right)

- 100~ grams of PLA Pro or equivalent/superior filament

- DB FCG Reinforcement Plate x2 (Optional)

## Instructions

Print at 0.2 or smaller, 6-10 walls, 100% infill, supports on build plate. Print as orientated or upside if you prefer.

Firstly, install M5 heat insert into the grip screw hole.

Then install FCG as you would on an AR, insert "Ejector_Spacer" into the ejector before installing into the lower, align the 

ejector hole with the corresponding hole in the lower before screwing the M3x12 into place.

## Pedigree

The following models/geomtry were referenced in the development of this project:

* "KF5" by NaviGoBoom/IvanTheTroll on The Gatalog

* Factory MP5 Lower

## Troubleshooting

- AR FCG issues

   *Most drop in triggers will interfere with the ejector, modification on trigger housing may be necessary

   *Rounded hammers are recommended (milspec hammers for example are rounded), square hammers will get caught on the bolt carrier

   *If your hammer is jamming up the action, either round off hammer or modify the carrier where it meets the bolt (see CETME AR FCG lower beta for more information, it's on odysee, however I don't recommend going to this length. This shouldn't be necessary for the MP5 however)

- Stock/Endcap not fitting over rear support

   *Sand the exterior of the rear support until it slides over, it should require some force, but not enough to deform or break anything.

## Change Log

- v0.13: Beta Candidate

    * MP5K Lowers added

    * Added DB-Firearms FCG Reinforcement variants

## License

No license has been selected as of 12/10/2023. No warranties expressed or implied. Use at your own risk.