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Shortly after its new contract with the U.S. Army, Sig Sauer has unveiled a new compact weapon, the MCX Rattler. According to, the Rattler is a compact personal defense weapon (PDW) built at the request of elite military units. The new weapon has the benefit of not needing a buffer tube in the stock like a conventional AR-15, allowing the rifle to host a more compact folding stock. As a result, the company claims that it is “shorter than any M4 ever produced.”

Sig Sauer’s new carbine goes even further, with a short 14-centimeter barrel,giving the carbine an overall length of just 40 centimeters when the stock is folded. The Rattler offers “M4 ballistics in a subgun-sized package,” the company says, a manageable weapon just a little longer than the ultra-compact MP5K.

In March 2017, the US Special Operations Command (SOCOM) released a Request for Information calling for a new conversion kit chambered in primarily .300 Blackout cartridge, but also the standard 5.56x45mm round. The command is apparently looking for a kit that can convert a standard M4A1 lower by adding a new upper receiver, a PDW that weighs no more than 2.5 kilograms and extends no longer than 66 centimeters with its stock folded.

The Rattler meets all of these requirements. Sig Sauer’s product page for the weapon explaining that the Rattler was “designed from the ground up to be as discreet as possible while retaining all the capabilities of the MCX.” In addition to a lightweight aluminium folding stock, the carbine also has a free-floating M-Lock handguard.