Sig Sauer M400 5.56 NATO 16" Semi-Auto Rifle, 30rd, Black - RM400-SDI-16B-P

The Sig Sauer M400 5.56 NATO rifle is a modern, feature-rich semi-auto platform built for shooters who want practical performance without compromise. With a 16-inch barrel, ambidextrous controls throughout, and thoughtful ergonomic upgrades, this rifle handles equally well whether you're at the range, hunting, or training. The M400 arrives ready to run with a matched trigger, quality internals, and the kind of build quality Sig is known for—it's the kind of rifle that rewards you immediately and won't need a parts catalog to become your go-to.

What sets the M400 apart is the attention to control and mounting. Full ambidextrous controls—including bolt catch, selector, charging handle, and magazine release—mean left- and right-handed shooters operate the rifle intuitively. The precision-machined upper and lower feature a handguard clamp system designed to keep your mounted optics and accessories stable, reducing deflection when you're running gear under recoil. The M-LOK rail system gives you real estate to mount lights, lasers, and other kit without eating into your grip real estate.

The trigger is a Sig flat-blade match trigger with a two-stage pull that breaks predictably, helping you place shots where they need to go. A hybrid flash hider/compensator manages muzzle signature and recoil, while the chrome-moly barrel with 1:7 twist handles a wide range of 5.56 ammunition. The Magpul SL stock is proven and adjustable, and the polymer grip is comfortable over long sessions. You get one 30-round magazine and all the ballistic capability of a mid-length 5.56 in a handy, 7-pound package.

Key Features

• Fully ambidextrous controls—bolt catch, selector, charging handle, and mag release work the same from either shoulder
• Precision-machined upper and lower with handguard clamp system to minimize accessory deflection
• Sig flat-blade two-stage match trigger for consistent breaks and shot placement
• Hybrid flash hider/compensator for muzzle management
• Chrome-moly steel barrel with 1:7 twist rate
• M-LOK accessory rail for optics, lights, and tactical kit
• Magpul SL telescoping stock for length-of-pull adjustment
• Direct impingement operating system—proven, reliable, easy to maintain
• Includes one 30-round AR-15 compatible polymer magazine

Specifications

Frequently Asked Questions

Is the M400 5.56 NATO good for hunting?

Yes. The 16-inch barrel and direct impingement system deliver reliable performance at typical hunting distances. The ambidextrous controls and adjustable stock make it versatile for different shooters, and the match trigger helps with accurate shot placement.

Can left-handed shooters operate this rifle easily?

Absolutely. The M400 features fully ambidextrous controls throughout—the safety selector, bolt catch and release, charging handle, and magazine release all work equally well for right- and left-handed shooters.

What's included in the box?

The rifle ships with one 30-round AR-15 compatible polymer magazine. You'll need to source optics and any additional mounting accessories separately.

What kind of accessories can I mount on the M-LOK rail?

The M-LOK handguard accepts any standard M-LOK mounting system—optics mounts, lights, lasers, foregrips, and slings. The handguard clamp system is designed to minimize deflection under recoil when gear is mounted.