SIG Sauer MCX Rattler .300 AAC Blackout Pistol – 5.5" Cold-Hammer-Forged Barrel, Fully Ambidextrous Controls
The MCX Rattler packs SIG Sauer’s battle-proven MCX gas-piston system into one of the smallest .300 AAC Blackout platforms available. Its 5.5-inch threaded barrel, monolithic upper with full-length Picatinny rail, and folding-capable design give shooters a compact, suppressor-ready pistol that retains the rugged reliability of the larger MCX line.
Condition
Overall Condition: Excellent condition, showing only faint signs of any prior use or handling.
Specific Condition Notes: This firearm is in great shape. There are some minor and superficial scratches and blemishes present. Bore is clean and shiny.
Bore Condition: Excellent – Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent Rifling – Sharp lands and grooves.
What’s Included
- (1) Magpul PMAG 300 BLK 30-round polymer magazine
- (1) Mission First Tactical 30-round polymer magazine
- Allen key
- SIG Sauer MCX Virtus operator’s manual and safety paperwork
- Factory SIG Sauer cardboard shipping box
The Rattler’s short-stroke gas-piston system is self-contained, allowing the pistol to fire with the brace or stock folded—a feature that sets it apart from buffer-tube-dependent designs. This compact form factor has been selected by USSOCOM under the RSAR PDW program, underscoring its real-world credibility.
The 5.5-inch carbon-steel barrel is cold-hammer-forged, nitrided for corrosion resistance, and threaded 5/8-24. A factory three-prong SIG flash hider is installed, and the fast 1:5 RH twist stabilizes both supersonic and subsonic .300 BLK loads, especially when suppressed.
Controls are fully ambidextrous—safety, magazine release, bolt catch, and extended charging handle—making the pistol equally intuitive for right- and left-handed shooters. The free-float alloy M-LOK handguard and monolithic upper provide ample space for optics, lights, and accessories.
Constructed from 7075-T6 aluminum with a hard-coat anodized black finish, the MCX Rattler offers durability without unnecessary weight. Quick-change compatibility across the MCX platform lets owners swap barrels and handguards to configure the pistol for specific missions or calibers.