It is no secret that the Eugene Stoner’s AR platform is the best selling rifle in the U.S. with many manufacturers jumping on the bandwagon in recent years by offering their versions. It seems the AR’s adaptability attribute is also its most abused quality. SIG Sauer is seeking to counterbalance this trend toward over-accessorized ARs with its SIG M400 Tread direct impingement AR.

SIG M400 Tread: ‘Room to Grow’

The M400 Tread is a SIG Sauer first in terms of creating an “entry-level” AR product. SIG has always resisted the entry-level product category, viewing it is only a race to the bottom in terms of pricing and quality.

However, typical of SIG, the Tread can be viewed as a premium entry-level offering, if that makes sense; that’s thanks to its ease of upgrading with SIG accessories specifically made to mate up on the Tread rifle. “Room to grow” is the SIG catch phrase with the Tread.

The SIG Tread naming pays homage to the Gadsden flag of the American Revolution. Most are familiar with the yellow background flag with a coiled rattlesnake with “Don’t Tread on Me” written under the snake.

Just as we depended on gun ownership at the birth of our nation’s independence, the same analogy can be made today as certain segments of society are back at it urging more and more government control in our lives; never a positive.

The SIG M400 Tread Build

The same SIG principles that guided its other rifle products, such as SIG516 and MCX Virtus, are present in the M400 Tread. The SIG Tread is a no-nonsense AR rifle. A collapsible buttstock is easily adjustable for length of pull and/or transport.

The M400 Tread is one of lighter AR versions on the market, especially considering that it features a full-length rail and stainless steel 1:8 twist 16-inch barrel. It weighs in at a svelte 7 pounds. SIG machines the low profile micro gas block found in Tread from stainless steel. It is much lighter than standard low profile gas blocks, helping to shave weight from the rifle and keeping it balanced properly.

SIG also used a mid-length gas system for a smoother recoil impulse. Ambidextrous controls are another nice touch with the base M400 Tread rifle.

The SIG Difference

There are two major aspects of the M400 Tread Rifle design that separate it from competitors. The first is the free float handguard design. A free float tube allows for better accuracy. SIG provides this while still allowing for accessories to be added.

Armorer training isn’t required to be comfortable with replacing the handguard and installing accessories. In fact, loosen two screws and, just like that, several length handguard options are available for use on the Tread.

This leads us to the second part of the Tread package. There is a line of fully proofed Tread accessories to take the base model to a more advanced realm. Those accessories include an ambidextrous charging handle, multiple vertical foregrips, metal BUIS sights, a three-chamber muzzle compensator, a 4.5-pound single-stage flat blade trigger upgrade, a SIG Romeo5 red dot and more.

All of these accessories come in distinctly labeled SIG Tread containers featuring the yellow Tread symbol, that way there’s no mistake that they’re viable for use with the M400 Tread AR rifle.

The SIG M400 Tread is a top choice for any AR connoisseur no matter if its your first rifle or 10th. Performance combined with price — it can be found starting around $799 in stores — is the quickest way to appeal to the shooting public. The M400 Tread will have no problem proving its worth.

And an update for September 2019, SIG just unveiled its SIG M400 Tread Pistol. The pistol variant puts a rifle caliber and a 30+1 capacity into a compact package with a barrel length of just 11.5 inches. For even more info, please visit

SIG M400 Tread Specs

  • Caliber: 5.56 NATO
  • Fram Material: 7075 Aluminum
  • Frame Finish: Anodized Black
  • Barrel Material: Stainless Steel
  • Sights: Optics Ready
  • Trigger: Single Stage Polished/Hardcoat Trigger
  • Overall Length: 30.8 inches
  • Overall Height: 7.5 inches
  • Barrel Length: 16 inches
  • Barrel Twist: 1:8
  • Overall Weight with Magazine: 7 pounds
  • MSRP: $951

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