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United States Special Operations Command (SOCOM) wants to convert its M4A1 carbines into Personal Defense Weapon (PDW) systems, and it’s ordering up commercially available Sig MCX PDW kits as a stepping stone toward accomplishing that goal.

According to a report in TheDrive’s War Zone blog, this all began in March of last year when USSOCOM issued a sources sought notice to industry for a PDW conversion kit. Here are the requirements that were listed on FedBizOpps:

PDW Kit specifics: The kit must be adaptable to the standard M4A1 lower receiver, any modification to the lower receiver must be reversible and nonpermanent. The kit must be in .300 Blackout (BLK) cartridge, total system weight, including the M4A1 lower in not to exceed 5.5lbs. Length with stock extended not to extend 26″ length with stock collapsed or folded shall be 17″ (T), 15″ (O) and a height not to exceed 7.5″. Weapon shall be fully functional when collapsed or folded. Kit should include a 5.56mm barrel that can be changed from .300 BLK to 5.56mm in less than 3 minutes. Accuracy shall be 3.0 MOA (T), 2.0 MOA (O) @100 yds. and 5.0 MOA (T), 3.0 MOA (O) @ 300 yds. both in .300 BLK supersonic. 

After sifting through responses, SOCOM announced on Feb. 1 via FedBizOpps that it was going with Sig Sauer. The reason? According to one of the accompanying documents, Sig was “the only company identified through market research that could provide the necessary MCX 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 PDW that meets the specifications identified in the sources sought notice.”

A full and open competition for the contract was not conducted because SOCOM said it “would not have been feasible given the operational necessity and urgency of the program,” and that “Sample systems are needed quickly to be used in formal combat evaluations that will be used to refine and define future requirements.”

Thus, Sig has been awarded a sole source, firm fixed-price contract for 10 MCX PDW kits, which will contain the following:

1.1.1 QTY: 10 Sig Sauer MCX PDW 300BLK Upper Receiver Group
(5.5) (PN: WUAMCX-5B-300B-BLK-TAP-AUTO)

1.1.2 QTY: 10 Sig Sauer MCX PDW 5.56 Barrel (5.5)
(PN: WCALX-MX-5B-556-TAP)

1.1.3 QTY: 10 Sig Sauer MCX PDW Suppressor Handguard
(PN: SIG-SRD300-999)

1.1.4 QTY: 10 Sig Sauer MCX PDW 300BLK Suppressor (Short)
(PN: 2401525-R)

1.1.5 QTY: 10 Sig Sauer SRD 7.62 Suppressor (PN: SRD762)

1.1.6 QTY: 10 Sig Sauer MCX Folding/Telescoping Stock
(PN: STOCK-X-FOLD-TELE-BLK)

1.1.7 QTY: 10 Sig Sauer MCX PDW Folding Skeleton Stock
(PN: STOCK-X-FOLD-THIN-BLK)

1.1.8 QTY: 10 Sig Sauer MCX PDW Stock Adapter Kit (PN: 2400557-R)

1.1.9 QTY: 20 Sig Sauer QD Sling Adapter (PN: SOCKET-1913-QD-LP)

1.1.10 QTY: 10 Polymer Rifle Case

1.1.11 QTY: 10 Wilcox BOSS 300BLK Optic (6-200) (PN: 64000G01)

1.1.12 QTY: 60 Sig Sauer Marked 300BLK Magazines (PN: 2400913-R)

1.1.13 QTY: 10 Sig Sauer Juliet 4x Magnifier (PN: SOJ41001)

Neither the FBO notice nor the accompanying documents mention it by name, but the War Zone notes that the caliber, 5.5-inch barrel length and folding skeleton stock are a match for the Sig MCX Rattler, which was announced last year and displayed at SHOT Show this year. In any event, the MCX PDW kits will be shipped to the U.S. Navy’s Naval Surface Warfare Center in Crane, Ind. for testing.

Sig MCX Rattler Specs

  • Caliber: 300 BLK
  • Frame Material: 7075 T6 aluminum
  • Frame Finish: Anodized
  • Barrel Material: Carbon steel
  • Barrel Finish: Nitride
  • Sights: Optics ready
  • Trigger: SIG Enhanced
  • Overall Height: 8 inches
  • Overall Width: 2.8 inches
  • Barrel Length: 5.5 inches
  • Barrel Twist: 1:5 inches
  • Overall Length: 19.3 inches
  • Weight with Magazine: 5.1 pounds
  • Trigger pull: 5.5-9 pounds
  • MSRP: $2,727 (SBR model)

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