Sig Sauer M400 TREAD Review: Is it the Best AR15 under $1,000 in 2020?

AR-15’s remain one of the most popular rifles in America, and there are thousands of variants that have flooded the market. If you are going to buy a firearm, you’ll find an AR15 in any budget, purpose, color, and in a plethora of calibers. Sig Sauer has been planning to bring in a high-quality, mil-spec, jack-of-all-trades rifle for a long time. That’s why in late-2018, they released their well awaited Sig M400 Tread Rifle.

Are you looking for a rifle that is affordable while retaining a high level of quality? If yes, the Sig Sauer M400 Tread is the right choice for you. It remains one of the best options when looking for an affordable AR that is versatile in use. It can be used in 3-gun competitions, recreational shooting, varmint hunting, self protection and anything in between.

Sig Sauer M400 Tread: A Quick Look

Sig M400 Tread Rifles are composed of aluminum receivers and are available in 5.56 NATO caliber. This optics ready rifle has a 16” stainless steel barrel, a free-floating M-LOK handguard, ambidextrous controls, a mid-length gas system, Magpul SL-K 6 position telescoping stock, and a single-stage polished/hard-coat trigger. This feature-laden and affordably priced rifle line is definitely one of the best AR-15s available in the market at around US$1,000.

The Sig Sauer M400 TREAD is far better in terms of looks and performance than the G.I. “M4”. In fact, it is much more competitively priced than other similarly featured firearms.

This AR-­15 rifle sports a slender 16-­inch stainless barrel, 5.56 NATO chamber, 1:8 twist rifling, pinned gas block, and a mid-­length gas system. When firing this rifle it provides you with a soft shooting experience, no matter what type of ammo is fired. The mid length gas system is highly reliable and provides you with a reduction in felt recoil as well as increased bolt life.

Sig M400 Tread Overview

One feature you may notice about Sig Sauer M400 TREAD Rifle is that the castle nut is mounted to the receiver extension properly. Though the proper staking of the endplate to the castle nut seems to be a minor assembly procedure, it makes a significant difference in ensuring the buffer tube assembly remains in place. Staking the castle nut results in more durability. It remains prone to unscrewing itself or coming loose when the staking is not properly done.

In fact, it was nice that the bolt carrier group has also been staked appropriately with the correct Grade 8 hardware. Proper staking in both the bolt and the castle nut provides your firearm with the well-needed reliability and dependability.

The lower receiver of the Sig M400 TREAD Rifle utilizes a built-in quick disconnect socket, which is another great addition from Sig engineers. The QD sling attachment makes it fast and easy to add a sling to the rifle.

Another feature from the factory that is worth mentioning is the 3-prong flash hider. This highly functional muzzle device reduces flash signature extremely effectively.  In addition to the proper gassing of the rifle, the muzzle device adds to its capability in the field.

The M400 TREAD comes with a 16” 416R stainless steel barrel featuring a mid-length gas system and 1:8 rifle twist. When firing this rifle, you will be extremely pleased by the smooth shooting experience. This is mainly because this Sig Sauer AR15 rifle comes with a mid-length gas system. The mid-length gas system results in a flat shooting rifle with smooth cycling, aiding the shooter in recoil mitigation and follow up shots.

When handling the Sig M400 Tread rifle in your hand, you’ll definitely adore the aesthetically designed standard 15” Tread handguard in MLOK. When you wrap your support hand around the slim grip, you’ll enjoy the stable platform.

The shooter is able to get an extremely comfortable grasp on the rifle due to the ergonomics of the ultra-slim handguard. You can really drive the muzzle on when transitioning targets while also reducing muzzle flip.

The trigger is very similar to single-stage triggers. However, it is better than most mil-spec triggers. The trigger weight is around 5-6 lbs and the best thing is that it is very smooth with little-to-no grit.

While using Sig Sauer M400 Tread Rifle, the best thing that you’ll experience is the ease of shooting fast controllably. The trigger included from the factory comes with a positive and quick reset. With quality ammunition, you can shoot sub-MOA groups without having the need to change the trigger to a match drop-in unit. The M400 Tread also comes with other enhanced controls.

It comes with a fully ambidextrous magazine release, oversized bolt release, and ambidextrous safety. The Feel of the rifle grip is similar to typical A2-style grips but with better ergonomics. The grip is a hallmark Sig design and its angle is very comfortable.

The M400 Tread has been incorporated with either Magpul SL-K or fixed stock and both of them are very comfortable. Though these stocks have a smaller footprint in comparison to other stocks on the market, both the size and weight work well.


Sig Sauer M400 TREAD Rifles are available in 3 basic models:

These models differ in terms of compliance with particular US states (such as CA – California or CO – Colorado), including mags, pistol grip, stock type, and trigger type.

Key Differences among these 3 Models:

MPN RM400-16B-TRD-CO RM400-16B-TRD-CA RM400-16B-TRD
Mag Type Single 10rd Polymer Mag Single 10rd Polymer Mag Single 30rd Polymer Mag
Stock Type 6-Position SL-K stock Fixed stock 6-Position SL-K stock
Trigger Type Single-stage polished/hard coated SIG Enhanced Single-stage polished/hard coated

Besides these key differences for compliance in certain states, all other aspects of these semi-auto AR-15s are absolutely the same. All three models have a stainless steel barrel, alloy forend, polymer grip, hard coat anodized finishe, direct impingement operating system, M-LOK accessory rail, 16 in (406.4 mm) barrel length, 5.56 NATO caliber, same dimensions (30.8 in x 2.5 in x 7.5 in / 782 mm x 64 mm x 191 mm) and same weight (7 lbs or 3.2 kg).

Combo Models

There are two combo models available:

RM400-16B-TRD-BDX model comes with:

a. Factory-mounted Sig Sauer Sierra3 3.5-10X42mm Riflescope

b. MAGPUL SL-K Telescoping Stock

c. Sig Enhanced trigger, and other features

RM400-16B-TRD-COIL model comes with:

a. Factory-mounted Sig Sauer ROMEO5 Red Dot Sight

b. MAGPUL SL-K Telescoping Stock

Sig Matchlite trigger, and other features


1. Ambidextrous Controls
M400 Tread rifles come with many ambidextrous controls, including an ambi-mag release and bolt release. The charging handle (made of aircraft-grade aluminum) is ambidextrous and comes with a dual roll pin design.

2. Free-Floating M-LOK Handguard
The M-LOK handguard comes with lightening cuts so that the weight can be reduced. They are available in 13” and 15” lengths. M-LOK front sight adapter and co-witness height are made up of lightweight aluminum. M-LOK grip kits, manufactured from high strength polymer, come in multiple configurations.

3. 16″ Stainless Steel Barrel
The Sig Sauer M400 Tread Rifle line has been incorporated with a medium-­light contour stainless steel barrel, which has a 5.56 NATO chambering, mid-­length gas system, and 1/8″ twist.

4. Flip-up Front and Rear Iron Sights
They are easy to install and are highly adjustable. The best thing is that they can be deployed quickly.

5. 3-Chambered Compensator
The 3-chambered compensator has been made specifically for the Sig Sauer M400 TREAD rifle. It helps in reducing recoil and muzzle rise with a 1/2 x 28 thread pitch. The manufacturer has also incorporated a SIG Sauer designed 3-­prong flash hider muzzle device on certain models of the Sig m400 Tread.


The Sig M400 Tread works smoothly in all shooting scenarios including running shooting drills on multiple targets at multiple ranges. In terms of speed and accuracy, this rifle makes shooting look easy. The handguard provides excellent ergonomics as well as modularity that will help shooters control their rifles and outfit them with needed accessories.

One of the best things about this rifle is how flat it actually shoots. This has become possible mainly because Sig has been successful in properly sizing the gas port on this mid-length barrel. These properly gassed mid-length barrels are quickly becoming the norm and this might be the one of the greatest features that is included from the factory.

Ergonomics & Reliability

  • Stainless Steel Barrel
    There are only a handful of AR rifles in the market that come with a stainless steel barrel and are still priced below $1,000. A stainless steel barrel is always preferable to other steels.
  • 5.56 NATO Chamber
    The 5.56 NATO chamber brings in a little extra sense of reliability, especially when the rifle has become dirty on the field. This is because the 5.56 NATO chamber is slightly bigger than that of the .223 Remington chamber.
  • 1/8″ Barrel Twist Rate
    Sig Sauer engineers have incorporated the 1/8″ barrel twist rate, which is best for handling a wide array of bullet weights. In a 16-­inch barrel, a mid-­length gas system optimizes reliability and reduces recoil. This is mainly because the pressure remains lower than in the shorter carbine-­length gas system. This makes the bolt move slower, thereby increasing bolt life on one hand, and reducing felt recoil on the other
  • Medium-­light Barrel Profile & Lightweight
    Sig M400 Tread Rifle has a medium-­light barrel profile, keeping the firearm lightweight. This is the reason why even after having a 15-­inch long aluminum handguard, the overall unloaded weight of the M400 Tread Rifle is just seven pounds.
  • Micro Gas Block is Pinned in Place, Increasing Reliability
    The Micro Gas Block on the TREAD is properly pinned in place, increasing the reliability of the firearm, no matter what the round count is, you can rely on the gas block remaining in place.
  • New 15-inch Handguard Design
    Sig has come up with a new, narrow (1.75″ x 1.5″) fifteen-­inch handguard design, which is proprietary to the TREAD. On the forward 2/3rd of the handguard, there are M-­LOK attachment slots at 3, 6, 9, and 12 o-­clock.

Pros & Cons

  • Sig Sauer M400 TREAD comes with a barrel that provides you with a minute of angle accuracy. With the proper choice of ammunition and in the right hands, you can get amazing accuracy.
  • These rifles have great quality, fit, and finish.
  • M400 TREAD has been incorporated with all kinds of enhanced features such as polished firing control group, ambidextrous safety, oversized bolt release, and ambidextrous magazine release. All these features are commendable additions to the original design.
  • The Magpul stock is an amazing feature. It not only looks good because of the minimalist look of the handguard but is also comfortable for different types of bodies.
  • Sig M400 TREAD has a decent weight along with a great balance, making it a treat for the shooters to shoot and keep it on your shoulders with a sling.
  • The manufacturer has included a rubber tensioning device in the rear of the lower receiver underneath the rear takedown pin. It helps by eliminating any play or rattle between the two halves of the receiver.


Rifle Name Sig Sauer M400 TREAD 5.56 NATO 16" 10rd. Black/Stainless Steel CO Compliant Rifle Sig Sauer M400 TREAD 5.56 NATO 16" 10rd. Black/Stainless Steel CA Compliant Rifle Sig Sauer M400 TREAD 5.56 NATO 16" 30rd. Black/Stainless Steel Rifle
Caliber 5.56 NATO 5.56 NATO 5.56 NATO
Barrel Length 16 in (406.4 mm) 16 in (406.4 mm) 16 in (406.4 mm)
Mags Included (1) 10rd Polymer Mag (1) 10rd Polymer Mag (1) 10rd Polymer Mag
Mag Type AR-15 AR-15 AR-15
State Compliant CO (Colorado) CA (California) -
Action Type Semi-Auto Semi-Auto Semi-Auto
Stock Type 6-Position SL-K Fixed 6-Position SL-K
Barrel Material Stainless Steel Stainless Steel Stainless Steel
Trigger Type Single Stage Polished/Hard-Coat Anodized SIG Enhanced Single Stage Polished/Hard-Coat Anodized
Twist Rate 1:8 1:8 1:8
Forend Type Alloy Alloy Alloy
Grip Type Polymer Polymer Polymer
Receiver Finish Hard Coat Anodized Hard Coat Anodized Hard Coat Anodized
Overall Length 30.8 in (782 mm) 30.8 in (782 mm) 30.8 in (782 mm)
Overall Width 2.5 in (64 mm) 2.5 in (64 mm) 2.5 in (64 mm)
Height 7.5 in (191 mm) 7.5 in (191 mm) 7.5 in (191 mm)
Threads 1/2 in - 28 tpi - 1/2 in - 28 tpi
Accessory Rail M-LOK M-LOK M-LOK
Operating System Direct Impingement Direct Impingement Direct Impingement
Weight (Oz.) 7 lbs (3.2 kg) 7 lbs (3.2 kg) 7 lbs (3.2 kg)
MPN RM400-16B-TRD-CO RM400-16B-TRD-CA RM400-16B-TRD

Bottom Line

The Sig Sauer M400 Tread Rifle is definitely one of the best mid-level AR-15 rifles available at a price point under $1,000. The inclusion of an upgraded handguard and pistol grip have made this rifle line more user friendly. While the mil-spec trigger is decent, the rugged structure makes it reliable enough for use in all fields and environmental conditions. Though there are cheaper options available, they don’t provide you with the same value for the money. The M400 TREAD cuts above most of the other starter rifles.

The most coveted aspects of this rifle are reliability, ergonomics, and accuracy. It provides you with a smooth shooting experience even after 800 rounds of firing. The accuracy is commendable, thanks to the excellent barrel and mil-spec trigger.  Sig Sauer has also included ambidextrous and enhanced controls in M400 TREAD Rifles, thereby taking the game above other manufacturers.

With a price of around $1,000, Sig Sauer M400 TREAD Rifle is definitely a great value entry-level rifle. It provides you with features that are usually found on more expensive rifles. Overall, the Sig Sauer M400 TREAD Rifles are a jack-of-all-trades platform, in which you can use for all kinds of shooting.

Once you choose this rifle, also take a look at the best AR-15 scopes and 5.56 ammo in order to properly outfit your new or existing platforms.


#1. Is the SIG m400 Tread a good rifle?

Sig Sauer M400 Tread is a great mid-level AR-15 rifle that comes with an upgraded handguard as well as a pistol grip. It comes with a decent mil-spec trigger. You can make a limitless upgrade to the rifle because Sig M400 Tread is primarily an AR-style rifle. It comes with amazing reliability and is available at a price of around US$1000, providing you with great value for the money.

#2. What is the Sig Sauer Tread?

Sig Sauer M400 Tread is an AR-pattern, optics ready, aluminum frame rifle that provides far better looks than G.I. “M4” and performance at a very competitive price of around US$1000. It features a 16” stainless steel barrel, a Magpul SL-K 6 position telescoping stock, a free-floating M-LOK handguard, ambidextrous controls, a mid-length gas system, a single-stage polished/hard-coat trigger, and a 5.56 chambering.

#3. Is the SIG m400 mil spec?

Yes, SIG M400 is built to full military specifications (mil-spec). It comes with a 16-inch chrome-moly steel barrel, a chrome-lined chamber, and bore. SIG Sauer M400 is available in three-round burst and fully automatic versions. These AR-style rifles are only available for use by both military and law enforcement.

#4. Where are Sig Sauer m400 rifles made?

The AR-15 style Sig Sauer m400 rifles are made in Germany.

#5. What caliber is a Sig Sauer m400?

Depending upon the variant you are choosing, Sig Sauer m400 is chambered for 5.56×45mm NATO, .223 Remington, and .300 AAC Blackout cartridges.

by Scopelist

Scopelist is a leading sports optics experts that stocks authentic binoculars, sporting optics, scopes, spotting scopes, riflescopes. Buy Nightforce scopes, Vortex Scopes, Zeiss Scopes & more at best price.