The Sig Sauer M400 X-Series in .223 Rem/5.56 NATO (brand part no. RM400-SDI-16B-P) is a semi-automatic AR-platform rifle built around a 16-inch chrome-moly barrel with a 1:7-inch twist, finished in Black FNC on a 7075-T6 aluminum receiver with a black hardcoat anodized finish. Sig Sauer wraps the barrel in a free-floating 15-inch M-LOK handguard, runs the Sig Flat Match Grade trigger, and fits a Magpul SL-K 6-position telescoping stock with a black polymer grip. The rifle features an ambidextrous safety control and ships with one 30-round magazine, threaded 1/2×28. Among AR-platform rifles in the AR rifles category, the M400 X-Series favors shooters who want a match-grade trigger in a proven duty-style build.

Key Specifications

• Chambered in .223 Rem/5.56 NATO with a 1:7-inch rate of twist.
• Features a 16-inch chrome-moly barrel, finished in Black FNC.
• Built with a 7075-T6 aluminum receiver, black hardcoat anodized.
• Wrapped in a free-floating 15-inch M-LOK handguard.
• Runs the Sig Flat Match Grade trigger.
• Fitted with a Magpul SL-K 6-position telescoping stock.
• Uses a black polymer grip.
• Features an ambidextrous safety control.
• Ships with a 30-round magazine, threaded 1/2×28.

Frequently Asked Questions

What trigger does this rifle use? The Sig Flat Match Grade trigger.

What stock does this rifle use? A Magpul SL-K 6-position telescoping stock.

Buy the Sig Sauer M400 X-Series 5.56 NATO

A match-grade trigger in a proven duty-style AR build is exactly what the M400 X-Series delivers. Order it from our Lubbock, Texas gun shop for fast, insured shipping to your FFL.