SOCOM to Evaluate SIG Sauer’s MCX Rattler

    Almost a year ago, back in March 2017, US SOCOM posted a request for information (RFI) seeking proposals for conversion kits for M4A1 Carbine receivers. SOCOM sought a kit that would turn M4A1s into Personal Defence Weapons weighing less than 6lb, measuring less than 26 inches and chambered in .300 Blackout.

    It seems SOCOM may have found what they are looking for, as a a notice announcing the Army Contracting Command’s intention to “solicit, negotiate, and award a sole source contract to Sig Sauer” for a conversion kit was posted on FedBizOps 1st February.

    The weapon the solicitation is referring to is SIG Sauer’s MXC Rattler micro carbine (Rattler being the weapon’s trade name). The solicitation notice, however, refers to the system as an “MCX Personal Defense Weapon (PDW)”. The Rattler, introduced back in August 2017, more than meets SOCOMs request measuring just 23.5 inches overall and weighs 5.7 lbs.

    The Army Contracting Command is planning to award a single sole source contract and posted the justification for this along with the solicitation notice.The notice states that:

    Sig Sauer was the only company identified through market research that could provide the necessary 10 each MCX Personal Defense Weapons (PDW) Parts and Kits which met the Government’s requirements for a Commercial off the Shelf (COTS) conversion kit for the M4A1 to create a Personal Defense Weapon (PDW).

    The SIG kit meets the Government’s requirements for a commercial off the shelf conversion kit but as the MCX Rattler is gas operated and uses twin recoil springs rather than direct impingement and a buffer tube the M4 lower’s will require a lower receiver adaptor that allows users to utilise the Rattler’s stock and MCX upper.


    New FN SCAR-SC with butt collapsed (FN America)

    While Heckler & Koch’s .300BLK carbine, the HK337, could in theory have been offered as a conversion kit, its overall length of 29.9 inches makes it too long for SOCOM’s specifications. It seems that FN also moved to fulfil the SOCOM request as the new FN SCAR-SC also fits the bill, despite being intially introducted in 5.56x45mm FN did confirm to Eric B back in November that the SCAR-SC would be available in .300 Blackout. The FN carbine also comes in under SOCOM’s required specifications but the SCAR could not be offered as a conversion kit for M4 receivers.

    A total of 10 kits will be ordered, these will include MCX PDW upper receiver groups, additional 5.56 barrels, suppressor handguards and suppressors, folding stocks and Wilcox Boss 300 optics and SIG’s 4x magnifier. The kits are destined for the Naval Surface Warfare Center in Crane, Indiana which developed small arms for the US Navy SEALs and other elements of SOCOM. The new PDWs are to be used to evaluate the system in combat operations, this may lead to larger orders or the seeking of alternatives.


    ‘Sig Sauer MCX PDW Kits Solicitation Notice’, FedBizOps, retrieved 05/02/18, from source

    ‘US Special Operators Will Test Sig Sauer’s New Mini Assault Rifle In Combat’, The Drive, retrieved 06/02/18, from source

    Matthew Moss

    _________________________________________________________________________ – Managing Editor – Managing Editor

    Matt is a British historian specialising in small arms development and military history. He has written several books and for a variety of publications in both the US and UK. He also runs Historical Firearms, a blog that explores the history, development and use of firearms. Matt is also co-founder of The Armourer’s Bench, a video series on historically significant small arms.

    Here on TFB he covers product and current military small arms news.

    Reach Matt at: [email protected]