Sig M400 Tread, Magazine and its cardboard box

SIG M400 Tread: Great AR Under $1,000

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There are a lot of AR-15 options out there. For this article we’re going to look at a relative newcomer that is a great shot, and that will set you back less than $1,000. Namely, the Sig M400 Tread.

This is a 5.56 NATO calibre rifle based on the venerable M4 and M16 designs. It also comes chambered for 300 AAC Blackout.

It is significantly less expensive than other AR-15-style rifles with similar specs and features. But is it as good?

The Tread comes with a slew of unique features and a full line of high-quality attachments. This firearm is a must-have for recreational shooting or hunting. Let’s take a brief look at this firearm’s pros and cons:

  • Optics-ready
  • M-LOK free-floating handguard
  • Flip-up front and rear iron sights
  • Ambidextrous charging handle
  • Inexpensive compared to other AR-15
  • Limitless enhancement options
  • Heavy trigger
  • Barrel gets hot

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Setting the Stage

Sig M400 5.56 NATO rifles
Sig M400 5.56 NATO rifles; Image by Greg-Lopez

5.56 NATO is standard on many AR-15s. It is regarded as a capable and flat-shooting cartridge, but we have not seen much innovation in this calibre lately. Therefore, it’s understandable that many manufacturers are striving to enhance other aspects of these rifles to make them even better. Sig Sauer’s M400 is a good example of this.

The M400 series is Sig’s traditional direct-impingement rifle line. The design is based on the classic M4 and M16 design, and the M400 is currently available in a variety of models. The Sig M400 series includes both rifle and pistol versions:


  • Sig M400 Classic
  • SRP
  • Tread
  • Elite
  • Predator


  • Elite PSB

All these weapons come with the standard M400 features like being cold-hammer-forged, 1-in-7-inch-twist barrel chambered in 5.56mm NATO, an M-Lok handguard, six-position adjustable buttstock, quick-detach (QD) sockets, and textured rubber pistol grip.

Sig Sauer Never Settle Logo
Sig Sauer Never Settle Logo; Image from Wikipedia

Because Sig’s series of M4-style rifles are both pricey and heavy, few people have become hooked on them. Sig Sauer wanted to address this and the M400 Tread is part of their answer.

It is a solid rifle with an improved handguard and pistol grip. The MIL-Spec trigger is fine, and there’s no limit to what you can do with it. The reliability is excellent, and the pricing is also very reasonable.

Given the pricing, factoring in an upgrade or two becomes more palatable as well. I’ll get back to some good upgrade options later in the article.

Why Go With Sig M400 Tread?

The New Face of Freedom, Sig M400 Tread Mantra
The New Face of Freedom, Sig M400 Tread Mantra; Image from Sig Sauer

There are so many reasons why you would love this rifle as I do. First of all is performance v price. A close second are the expansion possibilities. The Tread now serves as the foundation for Sig’s famed modularity. The M400 Tread is also a lightweight rifle, weighing about 7 pounds, which is due to its medium-light barrel design. 

Aside from a smooth shooting experience, the accuracy is also outstanding. Sig marketed this weapon as being extremely easy to shoot and versatile. That is something I won’t argue with. Plus, the Tread now features ambidextrous and improved controls, putting it ahead of the curve. 

If you enjoy both low-cost and high-quality guns, this is a weapon you should definitely take a closer look at. I think it’s one of the best options out there for a sub $1,000 AR.

So, let’s take a closer look at the specs.

Sig M400 Tread Specs

The M400 Tread is a direct impingement gas-operated magazine-fed weapon. It can fire 5.56x45mm NATO or .300 AAC Blackout rounds, depending on the version. This 5.56 NATO rifle has simple specs but is incredibly sharp in its performance.

Mag typeAR-15
Caliber5.56 NATO
Capacity30+1 rounds
Barrel length16 inches
Twist rate1:8
Weight7 pounds
Height7.5 inches
Operating systemDirect impingement
Action typeSemi-automatic
Barrel materialStainless steel
Grip typePolymer
Accessory railM-Lok

Who Is This Gun For?

The Sig M400 market consists of law enforcement, military, and civilian markets. Basically anyone interested in an AR-15 should consider this rifle.

Furthermore, the M400 Tread is ideal for those who are new to the AR-15 platform. These rifles are a strong alternative for those looking for a midpriced, general-purpose AR-15, whether for self-defense, hunting, and entry-level three-gun competitions.

The Sig M400 Tread Review


As you expectfrom Sig, the Tread appears to be well-made, with the nice build quality. The yellow “Tread” logo on the barrel will appeal to those who respect aesthetics and unusual weapons design. I don’t know if it’s just me, but I like it. You can remove it, though.

Sig M400 Tread, Magazine and its cardboard box
With its excellent build quality, the Sig M400 Tread doesn’t require a high-end casing.
Image by AntDogRascon

Moving on to what you’ll get out of the box. The rifle comes in a cardboard box with a Magpul PMAG 30-round magazine inside. You’ll also get the usual Sig M400 Tread manual, a National Rifle Association (NRA) card, lubricant, and one Sig Sauer sticker. The gun is ready to go right out of the box.

Hands-on Look and Feel

Sig M400 Tread Look and Parts
Sig M400 Tread; image from the  official site

In my view, the Sig M400 Tread has great looks and functionality. It is identical to the regular AR platform. It includes a revolving bolt and a direct impingement gas operating mechanism. The Tread has an aluminum frame, hard-coat anodized upper and lower receivers. 

Its gas key is staked appropriately, and the bolt carrier group (BCG) is made of steel. It also comes with a Magpul improved trigger guard as well as Sig’s own ergonomic pistol grip.

Sig M-Lok handguard and flash hider
Closeup shot of Sig M-Lok handguard and flash hider;
Image by Josh Miller

A free-floating M-Lok handguard for mounting optics also comes in handy. It sports a 16-inch stainless steel barrel with a 1:8 twist, which fits a variety of bullet weights. In addition, certain M400 versions include a three-­prong flash hider muzzle device. The three-chambered compensator is also helpful for reducing recoil and muzzle rise.

Sig M400 and loaded mag
Closeup shot of Sig M400 and loaded mag; Image by Uriah West

The ambidextrous magazine release has a simple design that should not cause you much trouble even after years of use.

There’s also an inclusion of a spring-loaded pin at the rear of the lower receiver. It allows you to adjust out any upper to lower movement. Its upper receiver is a flat-top AR upper with M4 feed ramps.

Closeup shot of M400 stock
Closeup shot of M400 stock; Image from Brownells

Yet another great touch is the lower receiver’s QD socket. As a QD sling user, I appreciate the concept of not needing to buy an aftermarket device to have this feature. Plus, it makes it very simple to attache a sling. 

The M400 Tread is also available with either a Magpul SL-K or fixed stock. The stock rests on a regular buffer tube with six configurations from which to choose.

Lastly, shooters may achieve a very comfortable grip on the rifle, you’ll appreciate its slender grip which is comparable to that of traditional A2-style grips.

Shooting the Sig M400 Tread


I was eager to get out on the range to see if this carbine could live up to its high reputation. So I immediately put it to the test. I was impressed by the hundreds of rounds of Sig’s Elite Performance 55gr .223 I put through the Sig M400 Tread. The Tread is a great shooter I must say, and there hasn’t been a single fail. When firing the M400 at 100 yards, the Tread groups well, coming in at 2 minute angle (MOA) with a five-round group. Even when the barrel grew burning hot, accuracy at ranges out to 100 yards is excellent. 

When it comes to the trigger it is superior to the majority of MIL-Spec triggers. It is incredibly smooth, features a solid and quick reset. However, there have been numerous claims that the trigger is hefty. Saying that, for me it worked fine, and those I have spoken to have not had any problems with it either.


The Sig Sauer M400 Tread proved to be quite reliable during the testing time I had with it. As mentioned earlier, even after a decent amount of rounds I kept hitting the targets. It’s relative simplicity means there are fewer parts that can fail.

First production was back in 2010 and reliability has not been an issue since.

Overall Performance

The weapon’s ability to shoot straight is one of its most enticing features. This is due to the rifle’s midlength gas system. The midlength gas system produces a flat-shooting rifle with rapid cycling. It also helps the shooter reduce recoil and make faster follow-up shots.

Additionally, the M400 Tread offers superb ergonomics and versatility. You can upgrade, attach or replace almost anything you can dream of in the AR world.

For me, the best part of shooting the M400 Tread is how easy it is to fire swiftly. I also like the control I have on every shot. Regardless of the ammunition you use, shooting this rifle is a smooth experience where you feel in control.

Sig M400 Tread Cleaning and Disassembly

As always, before field stripping a firearm, be sure it’s empty. To begin, set the selector to the safe setting. After pressing the takedown pin from left to right, swing the receivers apart. By pressing the pivot pin, separate the upper and lower receivers. After that, lift the charging handle to release the BCG from the upper.

Taking the gun apart isn’t that complicated. Check out Sig’s excellent user manual for disassembly. 

Cleaning the Sig M400 Tread is the same as cleaning standard AR-15. Before applying oil, make sure the barrel, bolt, and bolt carrier are all grease-free. Lubricate any moving parts before using the firearm at the range.

What Other Guns Compete?

Sig M400 Tread vs. M400 Elite

Let’s look at the Tread and Elite versions before moving on to other brands. There are more parallels than differences between the two. The upper and lower receivers of the M400 Elite are of the same high quality as the classic M400. The Sig M400 Elite differs in that it does not have ambidextrous controls. It also features internal parts with a diamond-like carbon coating. The M400 Elite also includes a 16-inch stainless-steel barrel and an improved Sig trigger that allows the shooter to obtain outstanding accuracy.

Sig M400 Tread vs. Colt M4 Trooper

The Sig Sauer M400 AR-15 rifle competes directly with the many Colt M4 carbines. Both rifles offer users advanced customization based on personal preference. At first look, the two rifles have a resemblance. The M400 Tread and Colt M4 Trooper both fire 5.56 x 45 NATO rounds. Both feature a 16-inch barrel and M-Lok accessory rail, standard M4 buttstock, and A2 pistol grip. The primary difference is that the Colt M4 Trooper comes with a Centurion rail. This allows for a wide leeway in optics mounting.

In addition, the Colt M4 Trooper is a bit pricier than the Tread. All in all, both Sig and Colt make nice rifles. You can’t go wrong with the Colt, in my opinion, it’s been tested in the field for quite a while. But Sig also make extremely well-made precision rifles. Both are fantastic to have.

Sig M400 Tread vs Springfield Saint Victor

The Saint Victor line of AR rifles is also out there to serve both the military and civilian markets. Like the Tread, Saint Victor Rifles has an M-Lok handguard and ambidextrous safety. The rifles are fairly reliable and perform well. You get a nickel-boron trigger that provides a grit-free draw for consistent accuracy. It also comes with basic flip-up sights ready to go out of the box.

But the Sig M400 Tread is still better priced, and almost all features are the same. Go with SIG and you’ll have more money for ammunition or upgrades.

Versatility and Modularity

This weapon is optics-ready, and the customization options are seemingly endless. Scopes and optics are obvious options with AR-style rifles. Improvements in grip and trigger are also common. It would also be a waste not to use the QD points and get yourself a sling.

When combined with Tread’s branded attachments, the user can customize their rifle to their liking. There are outstanding Sig Sauer products that you can get at a fair price. 
There’s also a factory-installed Sig Sauer Romeo 5 optics on the M400 Tread Coil model. But it’s not readily available on the standard M400 Tread. It’s yet another improvement option to the rifle.


Sig Sauer Romeo 5 

Unlike its other models, the M400 Tread does not include optics. If you want one, few compares to the Sig Romeo 5. This 2 MOA red dot sight comes with 10 different lighting settings and performs well. It is light, weighing only 5.1 ounces.

Rise Armament AR-15 Trigger

Super Sporting Trigger (SST) from Rise Armament is a popular choice for many users of the AR platform. It’s easy to install, has a sleek appearance, and a lot of enhanced engineering went into making it. It comes with a single-stage, 3.5 pounds pull weight and a curved or flat trigger blade. This trigger will work with your M400 Tread and is a great option for budget modifications.

Radian Weapons Raptor Ambidextrous Charging Handle

The Radian Weapons Charging Handle is compatible with a standard M400 upper receiver. I’ve seen others replacing the M400 Tread charging handle, and it works very well with them. I find this charging handle more attractive and useful than the factory model. Its ambidextrous design makes it easy to move around. The handles are made of 7075 aluminum, which is Mil-Spec and extremely sturdy. However, Radian Weapons charging handles cost $50 more than Sig.

Magpul Bipod

Shooting a rifle like the Tread accurately at distance necessitates support. A solid bipod is a great for this. When it comes to bipods they don’t come more solid than the Magpul. It’s Mil-Spec hard-anodized and lightweight. Plus it has a low profile design that hides its internal mechanisms and hardware, allowing it to glide over snags and bumps with ease. Leg extensions slide and lock securely, allowing you to expand the length of the legs by 4 inches from 6.3 inches to 10.3 inches.


The Sig M400 Tread is a bargain variant of the M4 type rifles. It’s a good choice if you’re searching for both a reliable and affordable AR-15. This weapon performs well and is a lot of fun to use. Its ambidextrous controls and high-quality build make it suitable in most scenarios.

The main benefit is of course that this weapon costs less than $1,000. Also, anyone can get it since it is now widely available for civilian use.

The Sig M400 Tread delivers on all fronts, and Sig’s dedication to the firearms industry is still unrivaled. Tell us what you think. We’d love to hear your thoughts in the comment box below.

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Feature image by AntDogRascon

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