Sig Sauer MCX Rattler Canebrake .300 AAC Blackout AR Pistol, 5.5 in Threaded Barrel, FDE/Black, Adjustable Gas Piston
The Sig Sauer MCX Rattler Canebrake is a compact .300 AAC Blackout pistol built around the MCX short-stroke gas piston system and configured for suppressed use. It features the SD extended handguard sized to shroud a suppressor, a 5.5-inch threaded barrel with the factory inert training device installed, and fully ambidextrous controls. The FDE/black finish and SB Tactical folding brace complete this purpose-driven package.
Condition
Overall Condition: Good condition, showing some signs of prior use and handling.
Bore Overall Condition: Excellent - Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent Rifling - Sharp lands and grooves.
Specific Condition Notes: The finish shows scattered scratches and small blemishes, with a few minor areas of discoloration in the FDE coating.
What’s Included
- 1x 30-round Lancer L5AWM polymer AR-15 pattern magazine
- Low-profile folding rear sight (installed)
- Factory inert training device (installed)
- M-LOK handstop (installed)
- SB Tactical arm stabilizing brace (installed)
The MCX Rattler Canebrake uses a semi-automatic, short-stroke gas piston system with a two-position adjustable gas regulator, supporting reliable operation and tuning when running suppressed. It includes an ejection-port cover and omits a forward assist by design.
Controls are fully ambidextrous, including the safety selector, magazine release, and charging handle with enlarged latches, plus a right-side bolt catch. A 1913 Picatinny rail on the upper receiver is paired with a separate short top rail section on the SD extended aluminum M-LOK handguard (not continuous), with the handguard sized to shroud a suppressor.
The 5.5-inch barrel is threaded and comes with the factory inert training device installed. Construction centers on an aluminum alloy receiver with an FDE finish paired to black components. The rear features a 1913 interface with a side-folding hinge and an SB Tactical arm brace with a Velcro strap.
Markings include "RATTLER" on the receiver plate, SIG MCX multi-caliber markings, and "SIG SAUER Inc. Newington NH USA." This U.S.-made configuration carries a 30+1 capacity and ships with a Lancer L5AWM magazine. Manufacturer part number is PMCX-300B-5B-TAP-CANE.