Sig Sauer M400 SDI XSeries 5.56 NATO 16" - AR-15 Rifle

A solid 5.56 NATO AR-15 without the fluff: the Sig Sauer M400 SDI XSeries 5.56 NATO 16" focuses on reliable function, practical configuration, and durable construction in a package ready to use straight from the box.

A semi-automatic AR-15 rifle chambered in 5.56 NATO, the Sig Sauer M400 SDI XSeries 5.56 NATO 16" combines direct impingement operation with standard AR-15 architecture for straightforward reliability.

Consistent Cycling: The direct impingement system delivers consistent cycling across the standard 5.56 NATO ammunition spectrum without requiring frequent cleaning or special maintenance.

Versatile Configuration: With a 16" barrel and standard AR-15 ergonomics, this rifle fits the broadest possible range of users and use cases without compromise in any single area.

Upgrade-Friendly Platform: Everything on this AR-15 is standard — stocks, grips, handguards, triggers, and optic mounts can all be upgraded without specialized tools or gunsmithing knowledge.

Weather-Resistant Finish: The Type III Hardcoat Anodized finish provides lasting protection against corrosion and everyday wear — reliable function from the first range trip to the last.

• Caliber: 5.56 NATO
• Barrel Length: 16"
• Gas System: Direct Impingement
• Handguard: Free-Float
• Muzzle Threading: 1/2x28
• Magazine Capacity: 30 Round
• Finish: Type III Hardcoat Anodized
• Origin: Made in the USA

Drop-in compatible with mil-spec AR-15 lower receivers. Takes standard STANAG magazines chambered in 5.56 NATO and works with the full range of AR-15 accessories and aftermarket upgrades.

The upper and lower receivers are constructed from 7075 aluminum with a Type III Hardcoat Anodized finish — a durable combination that resists corrosion and maintains tight tolerances over an extended service life.

Practical for home defense, recreational range use, and entry-level competition. Suits both first-time AR-15 buyers and experienced shooters looking for a dependable utility rifle.

SIG SAUER is trusted by the U.S. military and law enforcement agencies worldwide. Their AR-15 lineup delivers the same premium quality and engineering that earned SIG that trust. Made in the USA.