SIG Sauer MCX Rattler Canebrake PCB .300 BLK AR Pistol, 5.5 in Barrel, Coyote Tan, Folding PCB Brace, Adjustable Gas, Rear Charging Handle
The MCX Rattler Canebrake PCB stands out with its bufferless short-stroke gas piston system, true side-folding Pivoting Contour Brace, and SD-length handguard configured around a factory SIG Sauer inert training device. Purpose-built for .300 AAC Blackout, it uses a 5.5 in cold hammer forged barrel with a fast 1:5 twist and 5/8-24 threads, all finished in coyote tan Cerakote. This example includes three 30-round PMAGs marked 300 BLK and factory flip-up sights.
Condition
Overall Condition: Good condition, showing some signs of prior use and handling.
Bore Condition: Excellent - Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent Rifling - Sharp lands and grooves.
Specific Condition Notes: There are visible scuffs and wear on the exterior surfaces. The pistol appears to be in proper working order.
What’s Included
- Three 30-round Magpul PMAGs with 300 BLK ID bands
- Flip-up front and rear iron sights (installed)
- SIG Sauer Inert Training Device (7.62 mm), installed
The operating system is a semi-automatic, short-stroke gas piston design with no buffer tube, allowing the brace to fold flat via the 1913 hinge. A two-position adjustable gas block supports suppressed and unsuppressed use, giving the shooter easy tuning for .300 BLK loads.
The 5.5 in PDW-profile barrel is cold hammer forged carbon steel and nitride-treated, threaded 5/8-24, and cut with a fast 1:5 RH twist for .300 AAC Blackout. This Canebrake configuration includes the factory SIG Sauer inert training device installed to replicate suppressor size and weight during handling and training.
Controls and handling are modern and ambidextrous: rear charging handle, ambidextrous safety and magazine release, and SIG’s Matchlite Duo flat 2-stage trigger. It feeds from AR-15 pattern magazines and comes with three 30-round PMAGs clearly marked for 300 BLK.
The SD-length free-float M-LOK handguard (6061-T6 aluminum) runs a full-length 1913 top rail for optics and accessories. Factory flip-up iron sights are installed. The receiver is 7075-T6 aluminum with a coyote tan Cerakote finish, matched to the Pivoting Contour Brace in coyote tan and a black SIG polymer pistol grip.
Size and weight are compact and carry-friendly: approximately 29.25 in overall length when open and about 16 in folded, weighing roughly 6.5 lb. Markings include SIG MCX MULTI-CALIBER, RATTLER, and SIG SAUER INC., NEWINGTON NH USA. Made in the USA.