Sig Sauer MCX Rattler .300 AAC Blackout AR Pistol, 5.5-Inch Threaded Barrel, Short-Stroke Piston, Side-Folding Brace
This Sig Sauer MCX Rattler stands out for its compact 5.5-inch .300 AAC Blackout configuration, short-stroke piston system with an adjustable gas regulator, and internal recoil system that enables true side-folding operation without a buffer tube. Finished in matte black with an aluminum alloy receiver and handguard, it includes a continuous 1913 Picatinny top rail and SIG-branded folding arm brace. It is in excellent condition with only faint signs of prior handling.
Condition
Overall Condition: Excellent condition, showing only faint signs of any prior use or handling.
Bore Condition: Excellent - Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent Rifling - Sharp lands and grooves.
Specific Condition Notes: Very mild wear and light surface scratches are present from minimal handling and use.
What's Included
- 1x 30-round Magpul PMAG Gen M3 for 300 BLK (polymer)
- SIG Sauer MCX owner's manual
The MCX Rattler uses a semiautomatic, gas-operated, short-stroke piston system with an adjustable gas regulator that is accessible at the front of the handguard. This setup is purpose-built for the Rattler's compact format and .300 BLK chambering.
The 5.5-inch barrel is threaded and comes with a three-prong flash hider installed. Capacity is 30+1, and this pistol is chambered in .300 AAC Blackout (7.62x35mm).
An internal recoil system eliminates the need for a buffer tube and allows true side-folding operation. It is equipped with a SIG-branded side-folding arm brace and an ambidextrous manual safety selector for versatile control.
Construction details include an aluminum alloy receiver and a short ventilated aluminum handguard, both finished in matte black. A continuous 1913 Picatinny top rail spans the upper for mounting as needed. Markings include a side plate marked "RATTLER," an ejection-port cover marked "MULTI-CAL," and multi-caliber receiver markings on the magwell. The pistol uses a SIG polymer grip and is made in the USA.