The Sig Sauer M400 Forge is a semi-automatic AR-15-pattern rifle chambered in 5.56mm NATO. It has a 16-inch cold hammer forged steel barrel with a 1:7 twist and a mid-length direct impingement gas system, finished in matte Moss Green Cerakote. The rifle ships factory-equipped with a Romeo-MSR Gen II 2 MOA red dot and a 30-round magazine, giving it an optic-ready, out-of-the-box setup. 
 

Key Specifications 

• Brand: Sig Sauer 
• Model: M400 Forge 
• Caliber: 5.56mm NATO 
• Action: Semi Auto 
• Capacity: 30+1 
• Barrel Length: 16" 
• Finish: Moss Green Cerakote 
   

Detailed Features 

• 15-inch free-float M-LOK handguard for accessory mounting 
• TriggerTech 3.5-pound two-stage flat blade duty trigger 
• Factory-mounted Romeo-MSR Gen II 2 MOA red dot optic 
• Ambidextrous charging handle for use from either shoulder 
• 6-position Magpul SL-K stock for length-of-pull adjustment 
• Mid-length gas system tuned for the 16-inch barrel length

Shooters generally trust Sig's cold hammer forged barrels for durability, and the M400 Forge draws praise for running clean out of the box across various ammunition. The factory TriggerTech trigger gets noted as a step up from a stock mil-spec trigger, though a few owners still swap it for a personal preference.

Having the Romeo-MSR mounted and zeroed from the factory saves a step for buyers new to red dots, and the M-LOK handguard leaves room for a light or sling mount without extra parts. The Moss Green Cerakote finish is popular for hunting and range use, though a couple of owners mention finish wear shows at high-contact points over time.

Value-wise, bundling a rifle with an enclosed-style red dot tends to beat buying the two separately, which owners who were already planning to add an optic appreciate. AR-15 aftermarket support means handguards, stocks, and triggers are easy to swap later if preferences change.