Monarch Arms ARG3 – HK G3 Mag Fed AR10

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The H&K G3 and its clone the PTR91 (as well as other clones like the Century Arms C308) are some of the most popular 7.62 NATO battle rifles. Right up there with the FN FAL. They were proliferate in the German military so there is an abundant surplus of magazines. Well Monarch Arms has capitalized on the G3 pattern magazines and made a G3 magazine fed AR-10. Their hybrid is called the ARG3.

G3 mags are reliable and easy to find.

G3 mags are reliable and easy to find.

At the moment Monarch Arms is offering the ARG3 as a matched receiver set.

The Monarch Arms G3 compatible upper and lower pair.

The Monarch Arms G3 compatible upper and lower pair.

The receivers are listed for $550 and come as a matched set. Only their upper receiver will work with this lower. Monarch Arms is offering 80% versions of their lower receiver but it too will come with a matched upper receiver. Due to the G3 Magazine design, the ARG3 will not have a last round bolt hold open.

The Monarch Arms G3 compatible upper and lower left side.

The flip side.

The all new Monarch Arms ARG3receivers combine the best of new and old styling and functionality. The receivers are the ONLY current production receivers that accept HKG3 style mags as used commonly in the HKG3/HK91/PTR rifles (CETME MAGS MAY REQUIRE SOME MODIFICATIONS TO WORK).

The receivers are:

  • made from 7075 T6 grade aluminum
  • made in the USA
  • compatible with standard DPMS style parts
  • features a DPMS HIGH handguard compatible rail height
  • DO NOT feature a last round bolt hold open (G3 mag followers do not allow this feature)
  • utilize a proprietary upper/lower combo that only work together!
  • Raw bead blasted aluminum
  • 80% lowers compatible with the 5D pro and 80% arms jigs (no other jigs have been confirmed by us)
ARG3 80%

Monarch Arms 80% lower

Since AR-10s are not standardized like AR-15s, they patterned the ARG3 upper receiver to work with DPMS style parts. This is important when choosing a barrel and handguard. Also I assume you need to find a DPMS compatible bolt.

Here is a video showing the ARG3 functioning.

G3 magazines are plentiful in surplus and can cost as low a $5.99 on sale for the KCI Korean made magazines or if you want original H&K made magazines they are only $6.99. For more information on the ARG3, check out their website.

Nicholas Chen is a firearm aficionado. Growing up in California, He learned about firearms and hunted with his father growing up in Southern California. Once he moved out to Pennsylvania and then spent a few years in New York State, he learned to truly appreciate firearms and the second amendment. It was in New York State where he became a USPSA competitive shooter and learned about 3Gun. He is an avid fan of running and gunning. Nicholas is a fan of pretty much anything that shoots although the slicked-up race guns are what interests him the most. Having spent time with FFLs and other friends with NFA items he has begun his collection of NFA items and has learned that everything should be suppressed and full auto where possible and legal.

  • Bishop Alexander

    THAT is very interesting. I have been wanting to build an AR10 variation but was waiting for a different/ unique upper and lower look. I was considering a billet Aero Precision, but I think I may buy one of these.
    I’m one of the many that still has their 50 20rd magazines back when they were offered in the early 00’s as a 50 for $50 so I’m more than all set on mags. LOL!

  • Hector Rivera Jr

    I used to have a CMMG receiver set , that used G-3 magazines,that I used to build a custom DPMS pattern AR10. It was very finicky and magazine sensitive.

    I had to go through 30-40 magazines to find 7 that would feed reliably so I sold it at a huge loss.

    There is no point to this system as you can get cheap, reliable PMAG magazines for less than $15 each.