TFB Review: Genesis Arms Gen-12 – The 12ga AR-10

    An AR-pattern firearm that shoots shotshells is sort of a holy grail for some. Many try making it but there is always some drawback or compromise. ATI had their Omni chambered in .410ga. But the true goal is an AR platform that shoots 12ga. Genesis Arms has achieved that goal with their Gen-12. They lent us a 10.5″ firearm version for this review.

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    Genesis Arms based the Gen-12 around an AR-10 platform. Specifically, a DPMS Gen 1 308 patterned lower. Genesis Arms designed their upper receiver and magazine to function with those style of lowers. If you have a DPMS Gen 1 308 lower, you can simply buy one of their uppers and slap it on your DPMS Gen 1 lower. Load up their mags and you are ready to go. For better performance and reliability, Genesis Arms recommends upgrading your lower with their “Beef-Up Kit”.

    Photo by Genesis Arms

    The kit consists of:

    • anti walk trigger pin (x2) with screws (thread lock the screws with a medium strength product)
    • bolt catch
    • increased power bolt catch spring
    • magazine latch
    • increased power magazine latch spring

    Why the changes? The changes were made to increase function. The magazine spring needs to be modified to increase the “bite” in to the notch of the magazine, and a bevel needed to be added to aid in feeding the magazine. The bolt catch on a standard 308 will maintain contact with the GEN12 BCG so we had to grind off approximately .04″ to maintain proper cycling of the BCG. For similar reasons we needed to increase the spring power of the bolt catch, to keep the bolt catch from bouncing from the recoil produced from the 12 gauge.

    Don’t worry though. If you upgrade your DPMS lower with the Genesis Arms Beef-Up Kit it is backwards compatible with your AR-10 rifle caliber upper. No need to remove them to convert back to rifle or pistol.

    The upper receiver of the Gen-12 is completely proprietary though. The barrel, handguard, barrel block and BCG will not work on any other upper receiver.

    The Gen-12 operates on a short-recoil action. The barrel reciprocates. According to Genesis Arms, this is helpful for shorter barrels and eliminates the problem with gas systems fouling up found in AR platforms. The muzzle device is attached to the handguard and does not reciprocate. This design allows them to have breaching devices and suppressors on a reciprocating barrel.

    The Gen-12 upper does not have a typical AR-style charging handle. Instead, it is more like a semi-auto shotgun or AK-47. It has a fixed charging handle directly attached to the side of the BCG that sticks out on the right side. The bolt handle is threaded directly into the BCG and held with Loctite. You can remove it so you can field strip the BCG for cleaning. Just remember to clean the threads and apply Loctite again to keep the bolt handle in place.

    Genesis Arms sent in a complete 10.5″ firearm. I had originally hoped that I could use my Springfield Saint .308 pistol lower and just slap a Gen-12 upper on it. While the Saint is sort of DPMS-like, it is not compatible magazine-wise. The magwell is a bit too tight and would need to be modified to fit the Gen-12 magazines. The Gen-12 lower has all the same trigger controls as any AR-10. You can even use aftermarket triggers.

    I do wonder if a Franklin Armory Binary trigger or the Rarebreed FRT trigger could work in the Gen-12?

    I did try to install my Saint .308 pistol upper on the Gen-12 lower but the rear section of the lower sits too high and the charging handle drags across the top.

    What really makes the Gen-12 work well is the magazines. They fit AR-10 magwells (except for my Saint Victor pistol).

    When loading shells into the magazine, pay attention when using low brass shells. The rim of the top shell can get caught where the low brass starts and prevent the shell from inserting fully into the magazine.

    This is how the shells should be properly inserted into the magazine.


    Shooting The Gen-12

    The Gen-12 was widely well received by all who shot it. As soon as you hand it to a shooter, they instinctually know the manual of arms. “Oh, it’s like an AR?” is a common reaction. Since the Gen-12 is an AR platform, it was easy to accessorize it for night vision use. As you saw in the video above, I revisited night vision clay birds with my Lyman Trius Launchpad. Since it is an AR platform, it was easy to add a riser and mount the Meprolight RDS Pro V2 for proper night vision height. I added a Weltool W35 LH2 IR weapon light to help illuminate the florescent orange clays in mid-flight.

    Ballistic Magazine has a video about this shooting a full auto Gen-12.

    Final Thoughts On The Gen-12

    The potential is great for the Gen-12 especially if you have a compatible AR-10 firearm that can use the 12ga upper. You can shoot full-size 12ga shotshells or slugs and all you need to do is pop two pins and swap the upper. Any of their uppers, regardless of barrel lengths, costs $1,550. If you want a complete shotgun/firearm then they are $2,230. Genesis Arms offers 5-rd magazines for $23 or 10-rd magazines for $40. If you want to know more, go to their website.

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    Nicholas C

    Steadicam Gun Operator
    Night Vision & Thermal Aficionado
    Flashlight/Laser Enthusiast
    USPSA competitor

    Any questions please email him at [email protected]