The Sig Sauer SIGM400 TREAD is a semi-automatic rifle in 5.56x45mm NATO with an 11.5-inch barrel, 30+1 capacity, aluminum alloy receiver, Nitron finish, and a collapsible synthetic stock. It weighs 6 lbs and has a total length of 27 inches. The Picatinny rail runs the length of the upper for optics and accessory mounting. 
 

Key Specifications 

• Caliber: 5.56X45MM NATO 
• Action: Semi-Automatic 
• Capacity: 30 Rounds (30+1) 
• Barrel Length: 11.5 inches 
• Weight: 6 lbs. 
• Total Length: 27 inches 
• Grip Material: Synthetic Black 
• Receiver Material: Aluminum Alloy 
• Safety Type: Manual Safety 
• Barrel Twist Rate: 1:7 RH 
   

Features 

 
The 11.5-inch barrel makes this a short-barreled rifle configuration that requires appropriate NFA compliance. At 27 inches overall, it is highly maneuverable. The 1:7 RH twist rate stabilizes heavier 5.56 projectiles well. The Picatinny rail runs the full upper for optic and accessory mounting flexibility. The Nitron finish on the receiver and handguard holds up to field conditions. The collapsible stock adjusts quickly for different shooter lengths of pull or for transport.

The SIGM400 TREAD in the 11.5-inch configuration draws buyers specifically looking for a compact, NFA-compliant platform, and discussions reflect that focused use case.

Build quality is the most consistently praised attribute. Sig's manufacturing standards are well-regarded, and owners describe the TREAD as feeling solid and well-assembled. Accuracy for a short-barreled rifle in 5.56 gets favorable reviews, particularly at close to medium distances where the platform is most effective.

The Picatinny rail and modular design are appreciated by owners who run optics, lights, or other accessories. Swapping configurations is straightforward.

Price is the most common friction point. The TREAD costs more than comparable short-barreled AR builds from other brands, and some buyers feel the Sig premium is not always justified when comparing specs. Those who prioritize Sig's warranty and service reputation tend to be more comfortable with the price.

A few owners report minor out-of-box issues, such as feeding preferences or adjustments needed before the rifle ran consistently. These appear to be isolated rather than systematic.

Aftermarket parts for the M400 platform are less universally compatible than for mil-spec AR-15 builds, which limits some customization options compared to more established platforms.