CMMG G3 Mag Compatible AR-10 Lower

Steve Johnson
by Steve Johnson

CMMG are taking pre-orders for their new stripped lower reliever that is compatible with DPMS Panther Arms .308 AR-10 style upper receivers. The lower uses H&K G3 magazine which can be bought for under $5!

G3 lower (top)

Some minor modifications are needed to the upper to accommodate the larger magazine. The price is $449.95 and it can be ordered online.

Many thanks to Tom for the info.

Steve Johnson
Steve Johnson

I founded TFB in 2007 and over 10 years worked tirelessly, with the help of my team, to build it up into the largest gun blog online. I retired as Editor in Chief in 2017. During my decade at TFB I was fortunate to work with the most amazing talented writers and genuinely good people!

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  • AP NYgunlover AP NYgunlover on Jan 30, 2012

    This receiver is great, and compatible with any DPMS-style (LR-308 pattern) "AR-10" Upper receiver, after slight modification. I highly recommend it to anyone building a .308 AR, especially those who don't want to spend upwards of $50 for a single 20 round magazine, commonly the price in states with copies of the AWB still on the books. Here in NY, and across the northeast, pre-ban mags in horrible beat-up used condition including FAL inch or metric, original Armalite "waffle" AR-10, or even M1A/M14 20 round magazines routinely sell for $50 each at gun shows and in stores, as any high capacity mag from after '94 is not available to the civilian public. No Magpul P-mags for us... :(

    I own a PTR-91, an American built H&K-91, the civilian version of the G3 (also known as the CETME, same design,) .308 battle rifle still in use by dozens of countries' armies worldwide. I ordered about 50 H&K G3 pre-ban mags online for about $1 each a couple years ago. All were in great shape, most never used, steel or aluminum body, with HK factory markings and dates, ranging from the late 50's to mid 70's, no rust or slack in spring, all work as good as new.

    A couple years ago, when I first saw this CMMG Mk-8 .308 Lower receiver that accepted H&K G3 mags, I ordered it without hesitation, despite not having any plans to build a .308 AR. I was thrilled at the possibility of having an AR-10 style rifle, for which I already had a huge cache of magazines. I must say that it's a shame CMMG no longer sells this lower receiver, nor has any description or link regarding it on their website, I can only assume they no longer produce it either.

    I took my time building the lower receiver, researching extensively to find the best possible upper receiver assembly to fit the CMMG Mk-8 lower. The M110 Sniper system, SR-25 rifle had been gaining popularity at the time. Though completely out of my price range, I wanted to incorporate the best elements of the Stoner Rifle 25 in my build, including a 20" barrel, flat top upper with quad rail and rifle length gas system.

    The G3 rifle uses a delayed blow-back action with a forward cocking handle, the bolt does not stay open after the last round is fired and there is no bolt catch on the G3 magazine. Because of this, my .308 AR rifle with G3 mags built on a CMMG Mk-8 lower had no possibility for a bolt catch. To make the best of this, I settled on a Fulton Armory FAR-308 Titan complete Upper receiver. The Fulton Armory Titan offers a custom slick side cocking bolt carrier, allowing the user to bypass the standard AR charging handle and chamber a round by grasping the side cocking handle and pulling the bolt carrier back directly. This method feels natural, and much like chambering a round on an AK Pattern rifle, it is also very convenient for clearing stovepipes, double feeds, or re-racking after a failure to feed, FTE or other failure, of which I've experienced none. The standard charging handle still works fine, for firing from prone position, or if only my left hand is free, I'm glad I sprang for the ambidextrous charging handle, only $15 extra.

    With a JP Bennie Cooley Compensator on the end of the 20" barrel making it look like an M1 Abrams Tank, a 4x power Trijicon ACOG TA01B Scope, this rifle is a tack driver and the pride of my collection. Long story short, if you can find this lower receiver buy it. The great quantity and quality of compatible magazines available alone at such low prices is good reason, plus the receiver pattern LR-308 (DPMS style) is the most widely made and currently the standard for .308 AR rifles.

  • Mouse Mouse on Jul 23, 2013

    The link doesn't work for me...