SIG Sauer M400 SDI X-Series 5.56 NATO 16in 30rd

The SIG Sauer M400 SDI X-Series is a purpose-built modern sporting rifle chambered in .223 Rem/5.56 NATO with a 16-inch chrome moly barrel and a mid-length gas system for balanced cycling. The X-Series receiver set adds precision machining and ambidextrous controls, while the free-floating handguard supports modular accessory mounting. It ships with a single 30-round polymer magazine and a Magpul SL-style telescoping stock for adjustable ergonomics.

Key Specifications

• The caliber is .223 Rem/5.56 NATO.
• The barrel measures 16 inches.
• The barrel material is Chrome Moly Steel.
• The handguard is a 15″ free-float M-LOK design.
• The twist rate is 1:7.
• The trigger is a SIG Flatblade Match unit.
• The stock is a Magpul SL-K 6-position telescoping configuration.
• Included magazine configuration is 1 × 30‑round polymer magazine.
• The muzzle device is a hybrid compensator/flash hider.
• The unloaded weight is approximately 7.0 lb.

Engineered for dependable out-of-the-box performance, the M400 SDI X-Series pairs proven materials and ergonomics with a modular M-LOK fore-end and a match-style trigger to support accurate, repeatable shooting at the range or in training. Its combination of a mid-length gas system, precision-machined receiver, and accessory-ready handguard makes it a practical choice for shooters who value durability, control, and straightforward functionality.

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