The SIG Sauer M400 Forge 5.56 NATO rifle (SIG Sauer part no. RM400-556N-16B-FORGE-10) is an AR-15 built to come out of the case ready to shoot, with a factory-mounted ROMEO-MSR Gen II red dot already zeroed for close and mid-range work. This configuration feeds from a 10-round magazine, making it a solid option for shooters in capacity-restricted areas. It runs a 16-inch cold hammer forged barrel with an FNC finish and a mid-length gas system, paired with a 1:7 twist that stabilizes a wide range of 5.56 loads. A TriggerTech 3.5-pound two-stage flat blade duty trigger gives a clean, consistent break, while the free-float M-LOK handguard with a full-length Picatinny rail leaves plenty of room for lights and accessories. An ambidextrous charging handle and a 6-position Magpul SL-K stock round out a well-equipped carbine for range use, home defense or duty, and this Sig Sauer rifle is ready to run.

Key Specifications

• The chambering is 5.56 NATO, for reliable, widely available performance.
• The barrel is a 16-inch cold hammer forged barrel with an FNC finish.
• The twist rate is 1:7, which stabilizes a wide range of 5.56 loads.
• The gas system is mid-length, for smooth cycling.
• The trigger is a TriggerTech 3.5-pound two-stage flat blade duty trigger.
• The optic is a factory-mounted ROMEO-MSR Gen II red dot with a 2 MOA dot.
• The handguard is a free-float M-LOK design with a full-length Picatinny rail.
• The charging handle is ambidextrous, so it works from either side.
• The stock is a 6-position Magpul SL-K, adjustable for length of pull.
• Capacity is 10+1 from the included magazine, suited to capacity-restricted areas.

Frequently Asked Questions

Does the M400 Forge come with an optic? Yes. It ships with a factory-mounted ROMEO-MSR Gen II red dot with a 2 MOA dot.

What is the magazine capacity? This configuration feeds from a 10-round magazine, with a 10+1 total capacity.

What trigger does it use? A TriggerTech 3.5-pound two-stage flat blade duty trigger.

Buy the SIG Sauer M400 Forge 5.56 16-inch Rifle, ROMEO-MSR, 10-Round

Shooters in capacity-restricted areas who still want a fully equipped carbine should look closely at this M400 Forge configuration. Order it from our Lubbock, Texas gun shop for fast, insured shipping to your local FFL, and browse more AR rifles while you are here.