SIG MCX SPEAR SBR 7.62X51 13″ 20R CT

A 13-inch barrel chambered in 7.62×51 NATO delivers full-power rifle performance in a platform short enough for vehicle operations and close-quarters engagement. The MCX SPEAR SBR eliminates the traditional compromise between terminal ballistics and maneuverability, putting .308 Winchester energy on target from a package that clears doorways and fits inside compact bags.

Sig Sauer engineered the SPEAR around a gas-operated, short-stroke piston system that keeps heat and fouling away from the bolt carrier group. This design reduces carrier tilt, extends service intervals, and maintains reliability when suppressed—a critical advantage for the 13-inch barrel where dwell time is minimal. The 1-in-10-inch twist rate stabilizes the full spectrum of .308 projectiles, from 150-grain FMJ to 175-grain match loads and 168-grain hollow points, giving you ammunition flexibility across training, duty, and precision applications.

• 13-inch cold-hammer-forged barrel with 1:10″ twist maximizes velocity retention from the shortened platform while stabilizing heavy match projectiles
• Short-stroke gas piston system runs cleaner and cooler than direct impingement, critical for suppressed fire on a short-barreled .308
• Ambidextrous safety selector enables immediate manipulation from either shoulder without breaking firing grip
• Optics-ready flat-top upper with continuous 1913 Picatinny rail accepts any red dot, LPVO, or magnified optic without adapter plates
• Folding stock mechanism reduces overall length by approximately 7 inches for storage and transport
• One 20-round steel magazine included, compatible with SR-25 pattern magazines for widespread availability

The receiver set is machined from 7075-T6 aluminum with a hard-coat anodized finish that resists corrosion and wear in harsh environments. All controls—magazine release, bolt catch, charging handle—are fully ambidextrous, allowing left-handed shooters equal speed and ergonomics. The handguard features M-LOK slots at 3, 6, and 9 o’clock for accessory mounting without adding Picatinny weight, and the 13-inch length provides ample real estate for lights, lasers, and forward grips while leaving the muzzle device exposed for suppressor attachment.

At 10.8 pounds shipping weight, the SPEAR SBR carries the mass expected of a .308 platform, which translates to reduced felt recoil and faster follow-up shots compared to lighter short-barreled rifles. The package dimensions of 4.3 inches high by 11.4 inches wide reflect the folded configuration, making it compatible with standard discreet cases and vehicle mounts. As an ATF-classified Short Barrel Rifle, this unit requires Form 4 approval and tax stamp before transfer—plan accordingly for the NFA process.

This platform excels in roles demanding terminal effectiveness beyond intermediate calibers: vehicle-based security details, rural patrol where engagement distances exceed 300 yards, and home defense scenarios where barrier penetration and stopping power are paramount. The MCX SPEAR’s modular design allows caliber conversion kits for 5.56 NATO and 6.5 Creedmoor, protecting your NFA investment across mission profiles. Sig Sauer’s RSPEAR-762-13 B-SBR represents the current peak of short-barreled .308 engineering—compact without compromise.