[SHOT 2016] KRG’s Innovative FOX-42 7.62 Modular Rifle

Kinetic Research Group’s was for me one of the most interesting booths in the whole show. Justin, the CEO of KRG, is a delight to talk to for anyone interested in the details of small arms design. TFB’s Rusty S previously covered some of KRG’s other products, but left it to me to discuss one of their most interesting products: The FOX-42 semiautomatic precision rifle. KRG brought an early FOX-42 non-firing prototype to the SHOT Show last year to gauge interest, and apparently that paid off, since 2016 saw them bringing a fully-functional firing prototype, albeit still sporting some rapid prototyped components.

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The FOX-42 is a fascinating rifle, using a lightweight bolt carrier with an even lighter 4-lug, short-throw rotary bolt. Justin had ready answers to the tough nitty gritty questions I like to ask, such as “what’s the mass ratio of the carrier to the bolt?” (about 5-to-1, he says), and I was downright impressed with his grasp of small arms design theory.


A look at the 4-lug bolt of the KRG FOX-42.

The gas system on the FOX-42 is a direct impingement type, flowing into a hollow extension in the bolt carrier shaped like a de Laval nozzle, which gives the gas the correct thrust for operating the mechanism. Gas vents just forward of the receiver, according to Justin, so the rifle runs cleaner than an AR-15 without the excess weight and complexity of a piston gun, and while still achieving the quasi-free-floating effect possible with DI rifles. This also allows the operating group to be as light as possible, a distinct advantage in a precision semiautomatic rifle where a heavy, bucking mechanism can disturb a rapid follow-up shot.


Justin hinted to TFB that KRG had several other ideas in the works, as well. For the FOX-42, like all of the company’s projects, Justin said “it will be done when it’s done”.

Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He is also the author of the original web serial Heartblood, which is being updated and edited regularly. He can be reached via email at nathaniel.f@staff.thefirearmblog.com.


  • Hensley Beuron Garlington

    I’m intrigued. I look forward to hearing more about this direct impingement system and how it stands up to abusive and environmental conditions.

  • Kyle

    Where exactly does the gas vent? I am quite curious about this system. Sounds like a potential incremental improvement for ARs if it works well.

    • mechamaster

      Something like Tavor gas system. ( This is from SARG XS2012 concept rifle, patent listed from Magpul, maybe the designer of Masada / Massoud is the owner )

  • SpartacusKhan

    no buffer tube?

    • JumpIf NotZero

      Why would it have a buffer tube? Does the ACR have a buffer tube?

      • Vitor Roma

        Because it is DI and people associate DI with buffer tube since the long bcg of the AR requires one. But yeah, this gun has a different bcg that isn’t as long and I’m quite curios to see it.

  • J E

    Winning just by not having the idiotic buffer tube….wish someone would make a DI ar-15 with the carrier truncated and smaller buffer components it the saved area….

  • Justin Galt

    Great to see you again Nathaniel! We all look forward to the day when we can get you guys behind a full production version.

    The general concept comes from the AR-16/18, G36, Masada/ACR lineage. No buffer tube is used as the carrier and action spring are housed in the upper receiver.

    The gas vents in the forward direction, the location is above and just forward of the trunion. We’re not splitting the atom here but we think we’ve worked in some good enhancements.

    Justin (KRG)

    • Dave Curtis

      Sounds like a Tavor-ish operating system?

      • FactChecker90803

        Actually the Tavors operating system looks to be based on a Rifle from the 1980s, the Holloway HAC-7. The rifle was a Hybrid DI and Long Stroke piston.

    • mechamaster

      Is the gas system is something like the SARG XS2012 concept ?

      • Justin Galt (KRG)

        The basic concept is similar. There’s a gas tube bringing gas back to interact with a piston which is attached to the carrier. Other than that it is different in execution.

  • derfelcadarn

    Are there any rifles at the Shot Show that do not qualify as Buck Wodger’s Wightening Kwik Wabbit Kilwers ?