G-5 Billet Lower (Gen 2)

New Frontier Armory

As low as
(4 reviews) Write a Review
0.95 LBS
G-5 Gen 2 Lower
Pistol Cal
Black Ano or RAW (Media Blast Only)
Magazine Type:
7075 Billet Aluminum

Stripped G-5 Gen 2 Billet Lower (MP5 Mag)


Other Specifications and Features of the Stripped G-5 Billet Lower (MP5 Mag):

  • Machined from 7075-T6 aircraft grade billet aluminum
  • Available in Matte black hard-coat Type III anodize or RAW finish
  • Precision machined magazine well with beveled feed lip for easy mag swaps
  • Machined and engraved to be compatible with 45 and 60-degree short throw fire control selectors
  • Compatible with most standard AR-9 components and most aftermarket parts
  • Take down pin spring and detent hole is threaded for a 6-32 set screw for easy capturing (hardware included)
  • Upper tension screw behind grip screw (threaded hole with hardware included) to adjust any “slop” out of vertical fit between upper and lower
  • Ambidextrous countoured finger rests
  • Threaded bolt catch pin (Threaded hole and hardware)
  • Integrated large opening "winter" trigger guard
  • Proprietary magazine catch assembly, feed ramp, and ejector is included
  • Manufactured to MILSPEC (where applicable) on state of the art CNC equipment for consistent quality parts and exacting tolerances
  • Save money by building your own AR-9 rifle from the ground up exactly the way you want it configured and shoot for less!


  • **NOTE — You must use an upper that has widening cuts to accept the larger width MP5 Magazines — We sell three versions that are compatible, found HERE
    • C5UPPER
    • C5-NRSC Upper
    • PCUPPER-G2 (If using this upper, you must remove the LRBHO wire and reinstall the cover plate)

Pistol caliber specific LPK is available by CLICKING HERE

Magazines can be found HERE

**NOTE: ETS magazines will require slight sanding/filing to achieve a perfect fitment due to variations from factory H&K Magazines. We have yet to find any fitment issues with HK, Zenith, or KCI mags.



QUESTION: What type of magazines will fit in this lower?

ANSWER: The lower was designed to fit and drop free factory MP5 9mm magazines. It has also been thoroughly tested with many aftermarket magazines to fit and drop free. Although it accepts and shoots other aftermarket magazines (KCI, etc) some slight modification may be needed to get them to drop free from this lower because of the varying width measurement we have seen when checking these magazines to H&K MP5 factory specifications.

QUESTION: Do you offer a reliable last round / empty magazine bolt hold open (LRBHO) System for this lower?

ANSWER: NO, like the original MP5 platform, there is no LRBHO function. 

QUESTION: What bolt carrier group will work with a MP5 magazine fed AR-9?

ANSWER: The AR-9 BCG that we sell (CLICK HERE for AR-9 BCG) will work in our MP5 Mag AR-9

QUESTION: What LPK will work with this lower?

ANSWER: Although we sell a specific LPK with just the parts needed to build the C-5 lower receiver HERE, any standard AR-15 LPK will work. You will not need the magazine catch assembly, bolt catch roll pin, or trigger guard that are normally included with standard LPKs.

QUESTION: Do I need to use a special buffer when I build my AR-9?

ANSWER: Although its not technically required, it is advised that you either use a 9mm buffer (longer and heavier than carbine) or a spacer in your buffer tube before you place your spring in. The reason for this is to limit the BCG travel to the rear so it doesn't come back forward and smash the bolt catch hard enough to break it. The 9mm BCG is shorter than a standard BCG. You can use a carbine buffer with a spacer (WHICH YOU CAN PURCHASE BY CLICKING HERE).

The New Frontier Armory G-5 Stripped MP5 Mag lower receiver is proudly MADE IN THE USA by hard-working American men and women.


This is a serialized item considered to be a firearm by BATFE. This item must be shipped to a Federal Firearm License (FFL) holder. All BATFE, GCA & NFA rules apply! You will be prompted at checkout to pick an FFL to ship to in your area using our FFL Locate tool.

YOU will be responsible for checking with your local FFL to ensure this weapon is legal in the state that you reside and that they will accept this weapon on your behalf and transfer it to you. New Frontier Armory, LLC will NOT be responsible for any shipping or admin charges incurred by packages not being accepted by the FFL you choose during checkout.

Weight: 0.95 LBS
Dimensions: 9.50 x 4.50 x 2.25 in

4 Reviews Hide Reviews Show Reviews

  • 5
    Trying new style

    Posted by Alvin C Biggs Jr on 4th Jul 2024

    Love this product and made or should I say build a mp5 but in ar-15 style. And it works right and shoot smooth. Looking forward to buy another.

  • 5
    Pretty cool unit

    Posted by Carlos on 15th Apr 2024

    More fun than a neglected house wife!

  • 4
    MP5 Lower Receiver

    Posted by Patrick Ford on 6th Mar 2024

    Very happy with build quality and parts included, some duplication when ordering the LPK, but spare parts are always welcome. Assembly is finished and test fired today, super smooth action with only two comments. Trying to do a tactical reload with the bolt closed was not successful without a strong mag slam. Might be an MP5 issue. The other comment relates to the skeletonized grip attachment point. Being aluminum and only having several treads to grab onto, you better be dam sure of your grip screw alignment before trying to attach your grip. The anodizing may be filling the threads, and chasing the threads with a tap to clean them is advisable. I had some JB Weld on hand in case the screw went wild. Overall the carbine shot very well and I am very happy with my purchase, oh and if you have any questions for NFA , their response time was super quick.

  • 5
    Great lower

    Posted by Shane on 21st Oct 2023

    I paired this with the side charging upper and it's a great package, perfect if you're looking for something different from the standard glock-mag pattern AR9 lowers

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