SIG SAUER M400-FORGE 5.56 NATO 16-Inch Rifle

SIG SAUER M400-FORGE 5.56 NATO Rifle

The SIG SAUER M400-FORGE combines a forged-aluminum AR-style platform with a carefully selected group of factory-installed components. This listing is for manufacturer part number RM400-556N-16B-FORGE, the black 5.56 NATO model with a 16-inch barrel, 30-round magazine, and included ROMEO-MSR Gen II red-dot sight. Its configuration is intended to deliver a complete, optics-equipped rifle without requiring the buyer to assemble the core sighting, trigger, stock, and handguard package separately.

At the center of the rifle is a 16-inch cold-hammer-forged steel barrel with a 1:7-inch twist. SIG pairs that barrel with a mid-length direct-impingement gas system, a layout chosen to support smooth, consistent cycling in a practical carbine-length package. The muzzle is threaded 1/2×28 and fitted with an A2-style birdcage flash hider. The barrel, gas system, and muzzle setup make this model a familiar, straightforward choice for range practice, training, and general-purpose use.

Factory-Installed Optic and Trigger

This M400-FORGE arrives with a SIG SAUER ROMEO-MSR Gen II red-dot sight featuring a 2 MOA aiming dot. The optic gives the rifle a ready-to-use electronic sighting solution for fast target acquisition while leaving the full-length top rail available for compatible accessories. Because the optic is included as part of this exact factory model, buyers can evaluate the rifle as a complete package rather than treating an essential sighting component as an immediate add-on.

SIG also equips the rifle with a TriggerTech 3.5-pound two-stage flat-blade duty trigger. A two-stage design provides a defined initial take-up followed by a predictable break, while the flat trigger face offers a consistent contact surface. These characteristics can be useful for deliberate range work without giving up the practical controls expected on a modern semi-automatic rifle.

Modern Furniture and Controls

The free-floating alloy handguard provides M-LOK attachment slots along its length and a continuous Picatinny rail across the top. Its free-floating construction keeps accessory pressure off the barrel, while the mounting surfaces allow the user to configure lights, support accessories, or other compatible equipment for the intended role. The black anodized handguard and receiver maintain a cohesive, low-glare appearance.

A six-position MAGPUL SL-K adjustable stock lets the shooter tailor length of pull for body size, clothing, or shooting position. The reduced-angle grip supports a compact, contemporary stance. An ambidextrous charging handle and ambidextrous manual safety improve access from either side of the rifle, a practical advantage for left-handed users and for positional shooting. The controls remain based on the widely understood AR pattern, which helps keep handling familiar.

Key Features

• 5.56 NATO semi-automatic rifle
• 16-inch cold-hammer-forged steel barrel
• 1:7-inch twist rate
• Mid-length direct-impingement gas system
• 1/2×28 muzzle threads with A2 birdcage flash hider
• ROMEO-MSR Gen II red-dot sight with 2 MOA dot
• TriggerTech 3.5-pound two-stage flat-blade duty trigger
• Free-floating black anodized M-LOK alloy handguard
• Full-length top Picatinny rail
• Ambidextrous charging handle and manual safety
• Six-position MAGPUL SL-K adjustable stock
• One 30-round polymer magazine

Exact Configuration Details

SIG lists this model at approximately 35.5 inches overall with the stock extended and 32.25 inches collapsed. Listed weight is approximately 6.8 pounds before ammunition and additional accessories. The rifle uses an AR-15-pattern magazine and ships with one 30-round polymer magazine. Its receiver and handguard are finished in black, matching the stock and grip for a uniform factory configuration.

The M400-FORGE is designed for buyers who want a well-appointed factory rifle with meaningful upgrades already selected and installed. The cold-hammer-forged barrel, mid-length gas system, quality two-stage trigger, compact adjustable stock, free-floating handguard, and included SIG optic address the major components many owners consider first when setting up a new rifle. Before purchase, confirm that the rifle, magazine capacity, and included features comply with the laws and regulations that apply in your location.

Product Identification

• Manufacturer: SIG SAUER
• Model: M400-FORGE
• Manufacturer part number: RM400-556N-16B-FORGE
• UPC: 798681744114
• Caliber: 5.56 NATO / .223 Remington
• Barrel length: 16 inches
• Capacity: 30 rounds
• Finish: Black