Josh Wayner for TTAG
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The AR-15 is the everyman’s gun, America’s most popular rifle. It certainly didn’t start out that way, but, like it or not, it has captured both the interest and the ire of most of the world.

The semi-automatic AR-15 is representative of the American Dream, a device that, while common, is fiercely individualistic and adaptable to almost any circumstance. Today we are taking a look at the SIGM400 TREAD, SIG SAUER’s AR variant that offers a tremendous number of features at an affordable price.

The 5.56 NATO M400 TREAD is rather basic in its specs, but precise in its execution. The numbers are just like those we’ve seen many times before — a 16-inch direct gas gun with an Magpul SL-k 6-positon adjustable telescoping stock. But there is far more to it than that.

If you’re in the market for a hard-use, full featured AR that’s ready to rock right out of the box, the TREAD is hard to beat. I would say that, given the standard features, it’s hard to beat in the sub-thousand dollar range.

The features of the TREAD are many and all are functional. The TREAD is fully ambidextrous and is a joy to use at the range. Nothing about the controls are clumsy or poorly placed.

The stainless steel barrel is a 1:8 twist and is constructed of stainless steel, free-floating under a very rigid, smooth handguard. It has a mid-length gas system, which is my favorite as it smooths out recoil while not sacrificing reliability in a 16-inch barrel length direct impingement gun.

The SIGM400 TREAD has a single-stage trigger which, while somewhat stiff at the break, is crisp and easy to use for accuracy. Other features include M-LOK compatibility, a flash hider, and QD sockets.

If it feels like I’m brushing over features here, understand that I’m trying to get to the meat and potatoes which is how the TREAD performed in heavy testing. I beat this carbine up, never having cleaned it since I pulled it out of the box.Or at any part of my testing. I got it blazing hot and did many mag dumps.

The one takeaway you need from this article is that the SIGM400 TREAD is very, very difficult to tread on. Like a Timex, this rifle just keeps on ticking no matter what you put through it.

I didn’t have a single failure to feed or fire using three type of magazines, a wide variety of ammo, and in a range of competition conditions and field exercises.

The TREAD comes with a 3 prong flash hider. Those yellow plates seen above are removable.  (Josh Wayner for TTAG)

I tested all the ammo types that are likely to be fired through this carbine and I’ll elaborate on a few of them after the ballistics table. Testing was done over an Oehler 35P chronograph at a distance of five feet from the muzzle. Velocity is the average of ten rounds.

Groups are the average of three, five-shot groups fired at 100 yards off the bench with a Leupold Mark5 HD (fantastic scope by the way).

Black Hills 52gr Match HP—————-2957fps, .75″ (50 rounds)
Black Hills 50gr VMAX——————–2998fps, .75″ (50 rounds)
Black Hills 55gr TSX———————-3034fps, .75″ (50 rounds)
Black Hills 75gr Match HP—————-2525fps, .75″ (50 rounds)
Black Hills 69gr SMK———————-2699fps, .66″ (100 rounds)
Black Hills MK262 Mod 1——————2721fps, .50″ (50 rounds)
SIG SAUER 77gr OTM———————-2406fps, 1″ (150 rounds)
SIG SAUER 60gr HT————————2611fps, .75″ (50 rounds)
SIG SAUER 40gr Varmint——————3325fps, .9 (50 rounds)
SIG SAUER 55gr FMJ———————-2814fps, 1.25″ (300 rounds)
Hornady 73gr ELD————————-2600fps, .75″ (20 rounds)
Hornady Frontier 75gr Match————-2642fps, .75″ (100 rounds)
Hornady Frontier M193——————–3005fps, 1.5″ (350 rounds)
Hornady Frontier 55gr HP Match———2973fps, .75″ (100 rounds)
Hornady Frontier 62gr FMJ—————-3041fps, 1.3″ (200 rounds)

So this rifle was a solid 3/4 MOA performer off the bench when shooting with high quality glass. The groups I got were very consistent across bullet weights and brands.

I put 1,670 rounds trough the TREAD during testing and can say that the only thing I would change for bench shooting would be the hard-coat trigger. It’s a step up from mil-spec, but will never be confused for a match trigger

The stock may be a bit narrow in the butt for some, but it provides all the shoulder contact that most people could want considering that this gun will likely not be fired too much from a fully supported rest like it was during my testing.

Ambidextrous controls on the lower receiver and an ambi charging handle are standard on the SIG SAUER M400 TREAD (Josh Wayner for TTAG)

One thing the TREAD doesn’t come from the factory with is iron sights. The TREAD is, as SIG says, optics ready. Translation: there’s plenty of Picatinny rail space on top for a red dot, holographic sight or magnified optic.

I put a Trijicon ACOG on the TREAD to see how it would perform with a mid-powered, extremely rugged popular optic. The ACOG is a bomb-proof unit that’s made to be used on the AR-15 platform. The ACOG was zeroed at 100 yards with 62gr Frontier ammo and then taken out and put through its paces.

The TREAD logo is visible on the side of the ROMEO5 red dot sight. (Josh Wayner for TTAG)

I tested the gun and ammo in various carbine drills to include both precision and speed. The TREAD ran flawlessly.

A great thing I noticed was that it held zero very well, even while extremely hot. I have owned and shot many AR platform rifles that get sloppy when they heat up but the TREAD did very well in this department.

Its smooth, all metal handguard did a good job venting that heat, but it was a bit hot to the touch after a 300 round course I did in about a half hour. Gloves are recommended for heavy shooting sessions.

The Trijicon ACOG is right at home on the SIGM400 TREAD. (Josh Wayner for TTAG)

The overall impression of the TREAD at the time I stopped ACOG testing was overwhelmingly positive. Then I switched optics again to a SIG SAUER ROMEO5 TREAD red dot. This is a durable, affordably-priced and user-friendly sight that should appeal to most shooters.

I zeroed at 25 yards, then ran through many of the same speed and accuracy drills as I did with the ACOG. It worked wonderfully.

Note the QD sling swivels and comfortable SIG grip. (Josh Wayner for TTAG)

I did a number of up-close drills and simulated a 3-Gun competition on the range. The TREAD blitzed everything and was able to keep up with dedicated match guns in most areas (my custom guns did better in splits and recoil recovery, but not by much).

I was pleased by this and finished my testing with the belief that the TREAD is probably the best factory-built, sub-$1000 carbine out there. It has everything you need (other than sights), with room to be modified should you wish.

SIG SAUER killed it with the TREAD. With awesome guns like the MCX and M17 pouring out of their doors, it’s easy to miss a gun like this in the stampede. The TREAD is an AR-15 carbine that’s made to be used and not babied. It runs everything, has admirable out-of-the-box accuracy, and can be adapted to a number of end uses.

The SIG SUER M400 TREAD with its smooth M-LOK handguard is a solid performer that won’t break the bank. (Josh Wayner for TTAG)


Caliber: 5.56 NATO
Capacity: Ships with one 30rd mag
Barrel Length: 16 inches
Overall Length: 30.8 inches
Height: 7.5 inches
Twist Rate: 1:8
Sights: None
Weight: 7 lbs
Model: RM400-16B-TRD
MSRP: $950 (street price about $800)

Ratings (out of five stars):

Accuracy * * * * *
For an out-of-the-box carbine, the accuracy I got was great. A person looking for a general use sport/utility carbine would be well suited with the TREAD. It’s accurate enough for varmints out to 200 yards, but also heat resistant enough to be good for rapid-fire competitions while still holding zero.

Reliability * * * * *
I have had a fair number of AR carbines experience trouble getting off the ground. The TREAD fired everything with no complaints. Ejection was healthy and brass came out with force.

Ergonomics * * * * *
Like all AR platform rifles, it’s almost infinitely adaptable. Still, I find that many AR-15 rifles these days overcompensate for ambidextrous features. The SIGM400 is completely functional for lefties and righties.

Customize This * * * * *
This is an AR. The options are virtually limitless. SIG’s website also has a full host of TREAD accessories and then there’s the full universe of other aftermarket options. If you want it, it’s out there and will work on the SIGM400.

Aesthetics * * * 
Again, it’s an AR and looks like one. The TREAD won’t be mistaken for anything else. I like the choice of the Magpul stock and the handguard is smooth and clean. While it may not be eye-catching in a overcrowded AR field, it is certainly not crude.

Overall * * * * 1/2
The average guy out there — the great majority of potential AR-owners — will be well-suited with the SIGM400 TREAD. It offers a lot of sought after features at a reasonable cost, but the price is probably just a tad too high to be considered a truly entry-level rifle. I would say that, given the TREAD’s features and reliability, it is just about the perfect carbine for 98% of end users.

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  1. Looks good. And it’s not a a Springfield. What’s with “I didn’t clean it”?!? Imagine how great it’d run if you lubed it😎

  2. Pricing is kinda funny. $800 for this. Ok, great. Looks nice.

    I did an exercise on cheapness awhile back. I waited patiently for sales, deals, closeouts, cash leveraged discounts at shows, and managed to build a complete M4 for $312 bottom line.

    It has never failed me. I can’t remember anything other than a seriously random Failure-to-X, always caused by reloaded ammo. I would stake my life on it.

    As for accuracy compared to the above…hard to say. Different scope (“really nice”), younger eyes, better training, etc

    Buy vs build. I had fun doing it too. More fun than standing at a counter buying a box.

    • i just dont get buying a complete ar pattern rifle…
      building it gives it character
      and gives it a story
      it makes it your very own
      the build starts with an idea
      and then slowly the idea takes shape
      and when its done theres a sense of completion
      of accomplishment
      and the reward of the idea being a good one
      AND youll save money
      buy your handgun
      BUILD your rifle

      • The reason some of choose to buy a complete rifle is for multiple reasons. First, complete rifles usually come with a warranty. Second, complete rifles are much easier to sell and worth more if trying to sell or trade from my experience. Third, some of us don’t have the time or tools to build one. We just want to mount an optic and shoot!

        • Heck, I pay to have optics mounted. The older I get, the more I realize that actually shooting is what I enjoy most.

  3. A rip off of the Saint make an AR15 and give it a semi cool name and sell it as the best thing since sliced bread. It’s just as lame as the Rock River Arms RRage.

  4. I’d get rid of the yellow Tread banner forearm piece day one. I’ve had my eye on these at cabellas for 799 but I’m a .308 kind of guy.

  5. The Tread for a entry level AR with it’s fully ambidextrous features,45 to 50 for the ambi bolt catch/release,70 or more for a Norgon ambi. magazine release and you are no longer in entry price territory.

  6. im no sig fanboi
    having said that
    aesthetics…3 stars…
    cmon man…
    *it doesnt matter who made it*
    the all black 16 inch ar pattern carbine with slim mlok rail and 30 round mag is by far the best looking firearm in the history of small arms
    just look at it
    LOOK. AT. IT.

    • I looked, 3 stars.
      Want to see 5 stars? Look at a POF P308 SPR (18.5″ barrel) with triple port brake and finished in Robar NP3. THAT’S what 5 stars looks like.

      • Nah, those are nice looking, but for my money I haven’t seen a better looking AR than this one. (Except maybe those custom AR-10s Larry Correia had made for himself.)

        Looks *plus* performance…if I had $800 to spend on a rifle, I’d get me one of these. Well, really I’d probably build one. But if I were going to get one off the shelf, this would top the list at that price.

  7. My wife was ho-hum about ARs and didn’t want to pick out all the parts from a gazillion manufacturers, but when she saw this one at the hardware store, she had to have it. It was $875 at the store, $675 on GunBroker. Has the fit and form she likes, without the fuss.

  8. it ain’t cheap anymore (it’s Feb 2021) but it still seems like a good deal. This review was why I bought the package deal of the Tread with the BDX scope installed today at my LGS. Thanks for the review, Josh Wayner, it’s very helpful work.

    • range report 8 FEB 21: first range trip, the factory installed BDX scope was on the paper but low at 50 yards. It was easy to zero the scope, on 4th group of 3 shots, got a 1.5” group on the number 10 at 100 yards from small sandbag rest.

      if i can do this in the first 12 rounds, this rifle and scope combo is better than I am.

      Glad I read this review this past Saturday and “pulled the trigger” on the purchase.

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