Sig Sauer MCX Rattler SBR 5.56 NATO, 6.75 in Threaded Barrel, Adjustable Gas Piston, Ambidextrous Controls, Geissele SD Flat Trigger
This Sig Sauer MCX Rattler SBR in 5.56 NATO combines the MCX bufferless design with a compact 6.75 inch threaded barrel and a full suite of ambidextrous controls. It features an adjustable short-stroke gas piston system, a two-rod adjustable stock, and factory markings specific to the Rattler series. Upgrades include a Geissele Super Dynamic flat trigger and M-LOK accessories. This is an NFA item and will require a tax stamp and ATF registration.
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: The finish shows minor scratches and blemishes.
What’s Included
- Geissele Super Dynamic flat trigger (installed)
- M-LOK angled foregrip (installed)
- M-LOK hand stop (installed)
- 1x 30-round Lancer L5AWM polymer magazine
The MCX Rattler SBR platform uses a dual captive recoil spring assembly housed in the upper, eliminating the need for a buffer tube and helping maintain reliability in a compact form. The adjustable gas system supports tuning for various conditions, and the short-stroke piston action keeps the system running clean.
Controls are designed for true ambidextrous use, with safety selectors and magazine releases on both sides and a right-side bolt catch. The stock is an adjustable two-rod design with an approximate length-of-pull range of 9.5–12 inches, supporting fast handling in tight spaces.
The 6.75 inch steel barrel is threaded and fitted with a three-prong flash hider. A compact aluminum M-LOK handguard provides mounting slots on the sides and bottom, while a full-length 1913 Picatinny top rail runs across the upper and handguard. The receiver is 7075-T6 aluminum with factory markings including the RATTLER nameplate on the upper and SIG MCX MULTI-CALIBER on the magwell; the bolt carrier is marked MULTI-CAL.
This configuration includes a Geissele Super Dynamic flat-faced trigger for a crisp, consistent pull, plus an installed M-LOK angled foregrip and hand stop. It ships with one 30-round Lancer L5AWM magazine. The rifle is classified as a short-barreled rifle (SBR) and requires NFA transfer with an ATF tax stamp.