Sig Sauer MCX Rattler .300 AAC Blackout AR Pistol, 5.5 in Barrel, Short-Stroke Gas Piston, Matte Black
The Sig Sauer MCX Rattler is a compact, bufferless AR-style pistol built around the MCX architecture with a dual-rod stabilizing brace. This .300 AAC Blackout configuration uses a 5.5 in barrel and an adjustable short-stroke gas piston system. It features a full-length 1913 Picatinny top rail, ambidextrous controls, and a factory three-prong flash hider on its threaded barrel. Made in the USA, it includes one 30-round Lancer L5 Advanced Warfighter Magazine.
Condition
Overall Condition: Excellent condition, showing only faint signs of any prior use or handling.
Bore Overall Condition: Excellent - Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent Rifling - Sharp lands and grooves.
Specific Condition Notes: There are minimal markings from previous handling and use. See the photos for close-up views of the surfaces and markings.
What's Included
- 1x 30-round Lancer L5 Advanced Warfighter Magazine (polymer body with steel feed lips)
This MCX Rattler uses Sig's bufferless MCX architecture to keep the package extremely short while maintaining reliable cycling. The dual-rod pistol stabilizing brace with hook-and-loop strap complements the compact format and provides a stable interface.
The short-stroke gas piston action includes an adjustable gas regulator clearly marked with +/- icons, allowing the user to tune operation. The system is designed for dependable performance with .300 AAC Blackout in a 5.5 in barrel length.
Controls are fully ambidextrous, including the manual safety and paddle-style magazine release, and a left-side bolt catch is present. The pistol accepts AR-pattern detachable magazines and ships with a 30-round Lancer L5 Advanced Warfighter Magazine.
A full-length 1913 Picatinny top rail spans the receiver and handguard for mounting sights or optics. The barrel is threaded and fitted with a factory three-prong flash hider. Notable markings include a dust cover marked "RATTLER" with "MULTI-CAL" on the inside, plus receiver markings "SIG MCX MULTI-CALIBER" and "SIG SAUER INC., NEWINGTON, NH USA." The matte black finish completes the clean, modern look.