Sig Sauer M400 Tread Semi-Automatic Centerfire Rifle



The Sig Sauer SIGM400 TREAD semi-automatic pistol is a 5.56 NATO AR-15 type gun based on an 11.5” long barrel. This barrel has a 1 to 7” twist ratio, a 1/2″x28 TPI thread and is fronted by a birdcage flash suppresser. The TREAD rubric signifies the gun is part of Sig’s more affordable TREAD product line.

The carbon steel barrel has an FNC (ferritic nitrocarburizing) treatment that uses a salt-bath to mate carbon and nitrogen to the barrel for increased ruggedizing. The SIGM400 TREAD boasts a single-stage polished and hard-coated curved trigger that works in conjunction with the arm’s direct impingement system. In back is a Shockwave pistol brace ergonomically designed to combine comfort with lightweight flexibility.

The gun comes standard with Sig’s own black ROMEO5 1×20 red-dot optic. This nifty device is roughly 2.5” long by 2.5” tall by 1.5” wide. The ROMEO5 has ten illumination settings and a 2 MOA red dot, IPX 7 waterproofing, MOTAC (Motion Activated Illumination), and should be good for about 50,000 hours (over six years!) of battery life. That’s a really long time between battery swaps! As if that wasn’t enough, SIG also provides flip-up front and rear iron sights!

The aluminum receiver is hard coat anodized and crested with an integrated Picatinny accessory rail. The gun has an ambidextrous fire selector, ambidextrous magazine release. 

The important dimensions are its 7.5” height, 2.5” overall width and its 27” overall length. Total weight is only 6.0 pounds. 

The gun has a free-floating alloy M-LOK forend that’s further enhanced with lightening cuts. It has M-LOK slots on the sides and on top. The handguard is raised on top to hide the gas block and gas tube, but instead of having an angled bottom, the bottom is ergonomically curved for comfort. This semi-auto also has ambidextrous controls such as the ambidextrous aluminum charging handle making it usable by pretty much anyone.

The SIGM400 TREAD has a polymer grip with texturing on the sides and horizontal serrations in front and back. Moreover, the grip includes an integrated beavertail for a more comfortable hold.

The gun is nicely balanced and recoil and muzzle flip are easily manageable. The gun comes standard with a 30-round curved box polymer magazine.

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