Sig Sauer MCX Rattler .300 AAC Blackout 5.5" AR Pistol with Side-Charging Handle
This Sig Sauer MCX Rattler is a compact AR pistol chambered in .300 AAC Blackout with a 5.5" barrel and a short-stroke gas piston action. It features a bufferless layout with a rear 1913/Picatinny-style interface, a full-length top Picatinny rail, and iron sights including a folding rear. The receiver markings read "SIG MCX MULTI-CALIBER" and "SIG SAUER INC. / NEWINGTON / NH USA," with the upper receiver side plate marked "RATTLER" and the dust cover marked "300 BLK."
Condition
Overall Condition: Excellent condition, showing only faint signs of any prior use or handling.
Metal Condition: Excellent condition, showing only faint signs of any prior use or handling.
Wood 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.
Mechanics: Excellent condition, showing only faint signs of any prior use or handling.
Overall Finish: Excellent condition, showing only faint signs of any prior use or handling.
Specific Condition Notes: This firearm has some minor scratches and blemishes. The bore is clean and shiny. The muzzle device is not fully installed, and an A2 birdcage is currently acting as a thread protector.
What's Included
- 1x 30-round polymer AR-pattern magazine (body marked "5.56×45")
Built around the MCX platform, this Rattler uses a short-stroke gas piston system and a compact 5.5" barrel in .300 AAC Blackout. The dust cover marking "300 BLK" and partial barrel marking "300" match the chambering.
Controls and handling are centered on a right-side, side-charging handle with a ribbed/striated charging pad secured by two screws. Up front, it wears a ventilated metal handguard with elongated slots and integrated rail capability.
The upper is configured with a full-length top Picatinny rail and iron sights, including a folding rear iron sight. The receiver finish is a matte dark color, with metal receiver construction and clearly defined factory markings including "RATTLER" on the upper receiver side plate.
This example has a bufferless layout and a rear 1913/Picatinny-style interface, and it is being sold without a stock or brace present. The muzzle device is present but not fully installed, with an A2 birdcage currently used as a thread protector.