SIG MCX Rattler .300 Blackout Semi-Auto 5.5in 30rd M-LOK Folding PCB AR Pistol - PMCX-300B-5B-TAP

SIG MCX Rattler .300 Blackout Pistol: Built for Rapid Deployment

The SIG MCX Rattler delivers the full capability of the MCX platform in the most compact and concealable package SIG Sauer has ever produced, purpose-built for operators who need to move fast and stay discrete. Chambered in .300 Blackout and built around a 5.5-inch PDW barrel, the Rattler was designed from the ground up to go wherever it is needed without compromise.

• Model: MCX Rattler
• Manufacturer Part: PMCX-300B-5B-TAP
• UPC: 798681600182
• Caliber: .300 Blackout
• Action: Semi-automatic
• Type: AR
• Barrel Length: 5.5 inches
• Frame Material: Aluminum
• Finish: Black
• Stock: Folding PCB
• Handguard: Free-floating M-LOK
• Capacity: 30 rounds
• Accessories: Includes 1 magazine

The aluminum frame keeps weight low without sacrificing durability, and the included 30-round magazine means the Rattler is ready to run the moment it arrives. Whether for personal defense, duty use, or competition, this is one of the most capable compact pistol-format ARs available today.

SIG MCX Rattler Design and Handling Advantage

The SIG MCX Rattler was engineered from the start with one priority above all others: be as discrete and deployable as possible without giving up any of the MCX platform's proven capabilities. The folding pivoting contour brace collapses the overall profile significantly, making the Rattler easy to store, transport, and deploy from tight spaces. 

When extended, it provides a stable shooting platform that pairs naturally with the precision that .300 Blackout delivers, whether shooting supersonic or subsonic loads. Thin, agile, and fast-handling, the Rattler operates exactly the way you need it to when time and space are limited.

SIG MCX Rattler Configuration and Accessories

The free-floating M-LOK handguard runs the length of the PDW upper, giving operators a clean, customizable surface to mount lights, grips, lasers, or any other M-LOK compatible accessories without affecting barrel harmonics. 

The PDW upper keeps the overall length tighter than any standard MCX configuration, and the 5.5-inch barrel still generates meaningful terminal performance with .300 Blackout, especially with subsonic suppressed loads. The semi-automatic AR-type action gives the Rattler familiar controls and reliable cycling across a wide range of ammunition types, from lightweight supersonic hunting loads to heavy subsonic defensive rounds.

Why the SIG MCX Rattler Stands Apart

The SIG MCX Rattler occupies a unique space in the pistol-format AR category because it does not ask you to trade capability for size. The .300 Blackout chambering provides significantly more energy on target than comparable 9mm sub-gun platforms, and the folding PCB brace combined with the compact PDW upper makes the overall footprint smaller than most competitors while retaining every core MCX feature. 

The aluminum construction keeps the package lightweight and durable across hard use, and the black finish presents a clean, professional profile ready for duty or range work. For fast-moving operators who need a compact, hard-hitting AR-platform pistol that disappears when it has to and performs when it counts, the MCX Rattler is the answer.