SIG Sauer M400 SDI 5.56 NATO 16" Rifle FDE Telescoping Stock

The SIG Sauer M400 SDI delivers reliable semi-automatic performance in a versatile 5.56 NATO platform. This direct impingement rifle combines proven AR-15 ergonomics with SIG's manufacturing precision for consistent accuracy across multiple shooting applications.

What Makes This Different

The M400 SDI features SIG's enhanced bolt carrier group with improved coatings for extended service life. The 16-inch chrome-lined barrel provides optimal velocity for 5.56 NATO and .223 Remington cartridges while maintaining maneuverability. SIG's proprietary trigger group delivers a crisp break compared to standard mil-spec triggers, enhancing precision for both rapid fire and deliberate shots.

Key Features

• 16-inch chrome-lined barrel with 1:7 twist rate optimized for heavier bullets
• Flat Dark Earth Cerakote finish provides corrosion resistance and reduced glare
• 6-position telescoping stock adjusts for length of pull from 10.75" to 14.75"
• Free-floating M-LOK handguard allows accessory mounting without affecting barrel harmonics
• Enhanced bolt carrier group with nickel-boron coating reduces friction and fouling
• Ambidextrous safety selector accommodates left and right-handed shooters
• Standard AR-15 magazine compatibility accepts PMAG and USGI magazines

Field testing demonstrates consistent 2-3 MOA accuracy with quality ammunition, suitable for tactical applications, competitive shooting, and hunting medium game. The direct impingement system cycles reliably with both 55-grain and 77-grain loads. Weather-sealed components maintain function in adverse conditions, while the chrome-lined bore resists corrosion from extended storage or high round counts.

Technical Specs

• Caliber: 5.56 NATO/.223 Remington
• Barrel Length: 16 inches, chrome-lined with 1:7 twist
• Overall Length: 32.5" - 36.5" (stock collapsed/extended)
• Weight: 6.5 pounds unloaded
• Magazine Capacity: 30 rounds (where legally permitted)
• Finish: Flat Dark Earth Cerakote
• Handguard: Free-floating M-LOK compatible
• Manufactured: USA with lifetime warranty

This configuration balances portability with terminal performance, making it effective for multiple roles without compromising reliability. The FDE finish and quality components justify the investment for serious shooters requiring consistent performance.