SKU: SGPMCX-300B-6B-LT-PCB
UPC: 798681699759
MPN: PMCX-300B-6B-LT-PCB
The SIG Sauer MCX Rattler 300 Blackout 6.75" with pistol brace is a short-barrel, semi-automatic platform engineered for operators who need compact firepower without sacrificing ballistic performance. Built on SIG's proven modular MCX platform, this configuration pairs the proven 300 Blackout cartridge with a 6.75-inch threaded barrel in a compact form factor optimized for rapid deployment, vehicle operations, and close-quarters scenarios where traditional rifles prove impractical.
The 300 Blackout cartridge delivers substantial energy in a subsonic loading, making it ideal for suppressed operations while maintaining terminal performance in standard supersonic ammunition. The 6.75-inch barrel length optimizes velocity while maintaining the compact dimensions necessary for SBR-adjacent or brace-equipped platforms. A threaded muzzle allows installation of suppressors, flash hiders, or muzzle devices tailored to your operational needs. The anodized black finish resists corrosion across extended field use. The included pistol brace provides a stabilizing interface, and the platform ships with one 30-round magazine—standard capacity for the platform—giving shooters immediate capability out of the box.
This configuration serves law enforcement tactical teams, military support personnel, civilian operators seeking a do-it-all home defense platform, and precision rifle shooters who value the 300 Blackout's proven track record. The MCX platform's modular design means stocks, handguards, and rail systems can be swapped to match mission requirements. For those building a suppressed rifle system or needing a compact, magazine-fed solution with serious stopping power in confined spaces, the MCX Rattler in 300 Blackout delivers reliability and versatility in a proven SIG platform.
WARNING ⚠️
You must be 18 or older to purchase shotgun or rifle ammunition and 21 or older to purchase handgun ammunition and firearms. Please reference our requirements for ammunition orders to "restricted" states HERE. Always make sure you use the correct ammunition for your firearms. Ammo cannot be shipped to a PO Box. Please reference state & local laws before making a firearm or ammunition purchase.
Purchasing a Firearm? Click HERE to see our firearm purchasing guide.