What Are the Specs of the M400 Tread by Sig Sauer?
Woody's answers are based on published federal and state law. Not legal advice. Consult a licensed attorney for your specific situation.
The Sig Sauer M400 Tread is an AR-15 platform rifle chambered in 5.56 NATO with a 16-inch stainless steel barrel, mid-length gas system, 1:8 twist rate, and weighs 7.0 pounds unloaded with a 30.8-inch collapsed length.
How This Affects Your Build
The M400 Tread represents Sig's take on a mid-tier AR-15 with some thoughtful component choices that affect both performance and modularity. The specs show a rifle built around practical accuracy and reliability rather than cutting-edge features. Understanding these specifications helps you evaluate whether this platform fits your intended use case or if you'd need significant modifications.
The Detail
Starting with the barrel system, you're getting a 16-inch stainless steel barrel with a 1:8 right-hand twist rate and mid-length gas system. The stainless steel construction offers better corrosion resistance than standard carbon steel, while the 1:8 twist rate handles everything from 55-grain varmint rounds up to 77-grain match ammunition effectively. The mid-length gas system provides smoother cycling than carbine-length systems and typically shows less wear on components over time.
The rifle features a SIG M400 M-LOK free-float handguard that gives you modern mounting options without the bulk of quad rails. Free-floating the barrel means your handguard doesn't contact the barrel, which generally improves accuracy potential. The 3-prong flash hider is a functional muzzle device that reduces muzzle flash without the concussion issues you get with compensators.
For the lower end components, Sig went with a flat-trigger design rather than the standard curved military trigger. Flat triggers often provide a more consistent finger placement and can feel crisper than curved designs. The Magpul SL-K stock keeps the overall package compact with a collapsed length of 30.8 inches while maintaining adjustability for different shooters.
The overall weight comes in at 7.0 pounds unloaded, which sits in the middle range for 16-inch AR-15s. This weight suggests they didn't go ultra-lightweight with the barrel profile or components, but also avoided the hefty government profile barrels that can push weights over 8 pounds.
Build Impact
These specs put the M400 Tread in the practical shooter category rather than specialized roles like precision or ultra-lightweight builds. The component choices suggest this rifle works well as a foundation that you can modify incrementally rather than requiring major overhauls for most applications.