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

Quick Overview

The Sig Sauer M400 SDI XSeries is a performance-focused 5.56 NATO AR-15 rifle built for shooters who want premium features straight from the factory. Featuring a 16" carbon steel barrel, free-floating M-LOK handguard, SIG Flatblade Match Trigger, and ambidextrous controls, the M400 SDI delivers enhanced accuracy, improved ergonomics, and dependable reliability for defensive, recreational, and professional applications.

Built around a mid-length direct impingement gas system, the M400 SDI offers smoother recoil impulse and consistent operation. Combined with a Magpul SL stock, hybrid compensator/flash hider, and lightweight free-float design, this rifle provides excellent handling and performance right out of the box.

Key Benefits

• SIG Flatblade Match Trigger: Crisp break and improved trigger control for enhanced accuracy
• 16" Carbon Steel Barrel: Reliable performance and long service life
• Free-Floating M-LOK Handguard: Improved accuracy and accessory mounting flexibility
• Ambidextrous Controls: Bolt catch and release accessible from either side
• Mid-Length Gas System: Smoother recoil and reliable cycling
• Magpul SL Stock: Lightweight and adjustable for enhanced comfort

What's Included

• Sig Sauer M400 SDI XSeries Rifle
• 30-Round Magazine
• Factory Installed Magpul SL Stock
• User Documentation

Best For

• Home defense
• Range shooting
• Tactical training
• Duty and patrol applications
• General-purpose AR-15 use

Performance-Ready XSeries Configuration

The M400 SDI XSeries was designed as an out-of-the-box performance solution. Featuring upgraded controls, a premium trigger, and enhanced furniture, it eliminates many of the common upgrades shooters typically add after purchase.

SIG Flatblade Match Trigger

The factory-installed SIG Flatblade Match Trigger provides a cleaner break and improved trigger consistency compared to standard mil-spec triggers. This upgrade helps shooters maximize precision and maintain better control during rapid fire.

Mid-Length Gas System

The low-profile gas block and mid-length gas system work together to reduce felt recoil while maintaining reliable operation. The result is smoother shooting characteristics and improved overall rifle handling.

Free-Float M-LOK Handguard

The lightweight free-floating handguard helps maximize barrel accuracy while providing ample M-LOK attachment points for lights, lasers, grips, bipods, and other accessories.

Ambidextrous Controls

Featuring ambidextrous bolt catch and release controls, the M400 SDI accommodates both right- and left-handed shooters while improving efficiency during reloads and malfunction clearing.

Product Specifications