SIG MCX Rattler LT 300 Blackout SBR 6.75" Barrel 30-Round Black

The SIG MCX Rattler LT 300 Blackout SBR is a purpose-built short-barrel rifle that combines SIG's proven MCX platform with the ballistic efficiency of 300 Blackout—ideal for close-quarters shooting, suppressed setups, and tactical applications where compact size and modularity matter. This is the lighter, more adaptable evolution of the original Rattler, featuring a cold hammer-forged 6.75" barrel that keeps overall length to just 17.25 inches while delivering the subsonic and supersonic performance 300 Blackout shooters rely on.

Built around a short-stroke piston operating system, the MCX Rattler LT runs clean and reliably in suppressed and unsuppressed configurations. The adjustable gas piston lets you dial in the right amount of back-pressure for your ammunition and suppressor setup, eliminating the guesswork. Every control is fully ambidextrous—bolt catch, bolt release, and safety—so lefties and righties operate the gun the same way. The flat-blade match trigger is crisp and predictable, and the SIG suppressor-ready flash hider (SLX/SLH compatible) threads on without modification.

What sets the LT apart is its modularity. The barrel is now fully compatible with all MCX handguards and barrels in the LT lineup, so you can swap calibers, barrel lengths, and rail systems to adapt the rifle to your mission. M1913 accessory rails give you plenty of real estate for optics, lights, and other gear. At 5.8 pounds, it's nimble enough for CQB and tactical work while remaining solid enough for precision shooting at distance. One 30-round AR-15-pattern magazine comes in the box.

If you're running suppressed 300 Blackout or building a versatile short rifle that doesn't compromise on ergonomics or reliability, the MCX Rattler LT earns its place on the roster.

Key Features

• Cold hammer-forged 6.75" barrel in 300 Blackout with 1:5 twist for subsonic and supersonic loads
• Fully ambidextrous controls—bolt catch, bolt release, and safety operate from both sides
• Adjustable short-stroke gas piston for suppressed and unsuppressed shooting
• SIG suppressor-ready flash hider (SLX/SLH compatible) threaded and pinned
• 2-stage match flat-blade trigger for crisp, predictable breaks
• Modular design: barrel and handguard compatible with all MCX LT accessories
• M1913 Picatinny rail for mounting optics and tactical accessories
• Compact PDW grip for CQB and tactical handling
• Includes one 30-round AR-15 pattern polymer magazine

Specifications

Frequently Asked Questions

Is the MCX Rattler LT 300 Blackout suppressor-ready?

Yes. The rifle ships with a SIG suppressor-ready flash hider (SLX/SLH compatible) already installed and pinned. The adjustable gas piston also allows you to tune the rifle for optimal performance with a suppressor attached, whether you're running subsonic or supersonic ammunition.

Can I swap barrels and handguards on the MCX Rattler LT?

Yes. The MCX Rattler LT is fully modular. The barrel is compatible with all MCX LT barrels and handguards, so you can change calibers, barrel lengths, and rail systems to suit your needs.

What magazine does the MCX Rattler LT 300 Blackout use?

The rifle uses standard AR-15 pattern magazines. One 30-round polymer magazine is included in the box.

Is the MCX Rattler LT fully ambidextrous?

Yes. All controls—bolt catch, bolt release, and safety—are fully ambidextrous, making the rifle equally comfortable for left- and right-handed shooters.