The SIG M400 Forge 5.56 NATO rifle from SIG Sauer in Concrete Gray (SIG part no. RM400-556N-16B-FORGE-CON) is a modern AR-15 pattern rifle that comes with a ROMEO-MSR Gen II 2 MOA red dot. SIG Sauer builds it around a 16-inch cold hammer forged barrel with a mid-length gas system. A TriggerTech 3.5-pound two-stage flat blade trigger gives it the kind of crisp, predictable break shooters usually upgrade to. An M-LOK handguard, a 6-position Magpul SL-K stock and a Concrete Gray Cerakote finish round out a rifle ready for the range or home defense.

Key Specifications

• The chambering is 5.56 NATO, the standard military cartridge for AR-15 pattern rifles.
• The barrel is 16 inches, cold hammer forged steel with a 1:7 twist, built for durability and a wide range of bullet weights.
• The muzzle carries an A2 birdcage flash hider on 1/2-28 threads, which tames flash and allows muzzle device changes.
• The gas system is mid-length direct impingement, a balanced setup for smooth cycling.
• The optic is a ROMEO-MSR Gen II red dot with a 2 MOA dot, included for fast target acquisition.
• The trigger is a TriggerTech 3.5-pound two-stage flat blade, a duty-style trigger with a crisp break.
• The stock is a 6-position Magpul SL-K, adjustable for length of pull, with a reduced-angle grip.
• The handguard is M-LOK with a full-length Picatinny rail on top, so accessories mount anywhere you need them.
• The finish is Concrete Gray Cerakote, a durable coating that gives the rifle its color.
• One 30-round polymer magazine is included, and the rifle uses standard AR-15 magazines.

Frequently Asked Questions

Does the M400 Forge come with a red dot? Yes. It includes a ROMEO-MSR Gen II red dot with a 2 MOA dot, so it is ready to shoot with an optic.

What is the barrel twist and length? The barrel is 16 inches, cold hammer forged steel with a 1:7 twist.

How big is the rifle? SIG lists it at 35.5 inches overall and 32.25 inches with the stock collapsed. It weighs 6.8 pounds.

Buy the SIG Sauer M400 Forge 5.56 NATO Rifle with ROMEO-MSR Red Dot, Concrete Gray, 30-Round

The TriggerTech trigger and the included ROMEO-MSR red dot stand out most on this Concrete Gray rifle, and the M-LOK handguard and 6-position stock make it easy to set up. Order it from our Lubbock, Texas gun shop for fast, insured shipping to your FFL, and browse more AR rifles while you are here.