SIG SAUER M400 SDI RM400SDI16BP | 5.56 NATO | 16″

The SIG SAUER M400 SDI X-Series is a purpose-built modern sporting rifle configured around a 16″ chrome-moly barrel and a free-floating 15″ M-LOK handguard for accessory flexibility. It features upgraded ergonomics and controls, a SIG Flatblade Match trigger, ambidextrous controls, and a Magpul SL-family telescoping stock for familiar AR-style handling. For an optic under $1,000 that pairs well for close-to-mid-range work, consider a Vortex Strike Eagle 1-6×24 for quick target acquisition and effective precision out to several hundred yards.

Well suited to range and competition use, the M400 SDI X-Series also functions as an effective option for varmint or small-game field work where a lightweight, accurate 5.56 platform is appropriate.

Product Specifications

• The caliber is .223 REM/5.56 NATO.
• The barrel is made of Chrome Moly Steel and measures 16 inches.
• The action type is Semi-Auto.
• The handguard is a 15-inch free-float M-LOK design.
• The stock is described in source data as a 6-position Magpul SL-style telescoping stock.
• The trigger is a SIG Flatblade Match unit.
• The muzzle device is a hybrid compensator/flash hider.
• The package includes 1 × 30‑round polymer magazine.
• The listed weight is 7 pounds.
• The overall length is listed as 36.5 inches.
• The rifling twist rate is reported as 1:7.
• The barrel thread pattern is 1/2-28 tpi.
• The receiver is finished in black hardcoat anodized 7075-T6 aluminum.
• The UPC is 798681664634.

The M400 SDI X-Series combines upgraded controls, a match-style trigger, and a rigid free-floating handguard to deliver a refined, out-of-the-box performance rifle for informed shooters. Its feature set favors controllability and modularity on the range or in competitive formats, while remaining a straightforward platform for customization. If you value solid factory ergonomics, reliable operating components, and a common accessory interface, this SIG Sauer M400 SDI presents a balanced package that rewards further upgrade or optics selection.

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