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SIG Sauer M400 Review

by Kevin R. Davis   |  November 2nd, 2012 26


SIG Sauer is a company name that is synonymous with quality firearm design and execution. Touring the factory, I saw new machining capabilities and quality-control measures operating in perfect function. At the time of my visit, the company had just invested millions to further its goal of being the finest maker of small arms in the world. At the SIG Academy I got my hands on the entire product line and was permitted to shoot everything from pistols to sniper rifles.

As a full-time LE firearms instructor and former carbine instructor-trainer for the state police academy, I seldom pass up an opportunity to fire a well-made carbine. And that’s exactly what the M400 is.

The SIG Sauer perspective, according to Jarrod McDevitt, rifle product manager, is that the M400 is customer driven with direct requests from LE that specifically desired an M4-style carbine.

“Based on popular demand from law enforcement,” says McDevitt, “we designed an M4 carbine with a better price point that includes all the fine manufacturing and quality customers have come to expect from SIG Sauer.”

Currently, SIG Sauer is in negotiations with several agencies in the U.S. considering the M400 for department purchase. McDevitt pointed out that select design features of the SIG Sauer M400 product line offer both citizens and police officers even more to choose from. At this time, the hottest-selling model is the M400 Enhanced FDE with flat dark earth forearm and stock, with SIG Sauer offering the same finish on the upper and lower receivers. The company offers many of the features customers must purchase on their own “out of the box,” which is a refreshing concept.

The M400 has a 16-inch chrome-lined barrel with a 1:7-inch twist. This flattop shooter comes with a detachable carry handle sporting A2-style adjustable rear sights. The entire package weighs just 6½ pounds empty.

The trigger is listed as 7.6 pounds, but my Lyman trigger-pull gauge averaged my sample at 7.1 pounds. I found the trigger smooth to operate with a clean break.

The forearm is a standard carbine-length six-inch design. The buttstock is of the six-position adjustable M4 style.

According to SIG Sauer, the lower receiver is forged 7075-T6 aluminum and contains many unique design features that set it apart from the classic M4 it emulates. For example, there are four vertical grooves on the front of the magazine well to improve grip for those who prefer to place their support hand at the delta ring/mag well area.

Inside the lower, SIG Sauer has included a spring tension plunger “Accu-tensioner,” which places upward pressure on the rear takedown pin. The thought is similar to polymer wedges often employed in this area to reduce movement and play between the upper and lower halves, thereby enhancing accuracy. Now, I’ve always been honest enough to state that most carbines shoot better than I do, so attempts to improve accuracy by making the fit tighter, while appreciated, are not needed. That said, the design is standard on the M400 and not an additional expense.

Let’s face it, it’s a right-hander’s world. And if they have to, southpaws can learn to run the gun on the M4 with practice. I’ve seen several who do an excellent job with a traditional magazine release, but it does take practice and is not as efficient as a rifle operated by a right-handed shooter. Ambidextrous mag releases are available aftermarket.

SIG Sauer has thought to include one on the M400 and has even built up a protective fence similar to the one that protects the right-side mag release. An accomplished shooter and armorer associate of mine expressed concern that the placement of the left-side mag release, which lies close to the bottom of the bolt catch, would interfere with locking the bolt to the rear, especially when wearing gloves. Such was not the case, as I was easily able to perform this function while wearing standard patrol-style gloves. Heavier gloves may cause a problem, but they would regardless.

Also included in the M400 lower are two sockets where the operator can attach QD sling swivels or a single-point sling with a push-button release. This is an excellent improvement to the M4 concept that saves the user additional expense via modern engineering.

Shooting the M400
Prior to taking this SIG Sauer carbine out to the range, I removed the carry handle and replaced it with the new Aimpoint Patrol Rifle Optic (PRO). As a firm believer in the efficiencies of red dot sights for law enforcement, the PRO has most of the benefits of Aimpoint’s fine line of collimator sights, but at a substantially lower cost. This is certainly appreciated in these budget-crunching times when many law enforcement officer are paying for their own rifles and optics. Also quickly installed was a Blackhawk Deiter sling.

Not included on the M400 is a quad-rail forearm. The standard AR forearm works well but does not allow a white light that I’m partial to mounted on the rifle. This is easily solved by an aftermarket mount that places a small section of Picatinny rail next to the front sight tower or by purchasing an aftermarket quad rail forend system.

With a quick 50-yard zero, I did most of my work with the M400 at 50 feet and inside. After hundreds of patrol and SWAT situations in which I’ve pointed all matter of firearms at people, they’ve all been inside 50 feet, with most at room distance. My usual repertoire of carbine skill drills includes stepping off line while raising and firing, 90- and 180-degree facing movements, kneeling, prone and shooting on the move in either a slower “search speed” or faster “raid speed,” eventually picking up the pace to include “hostage rescue speed.” The last is essentially moving as fast as I can accurately shoot. The carbine drills included reloading with retention, (i.e., tactical reloads), as well as reloads without retention (a.k.a. speed reloads). The SIG Sauer M400 functioned flawlessly with the aforementioned trigger and fine ergonomics of the M4 design. Execution proved flawless functioning, as I expect from anything coming from SIG Sauer.

The Case for the Carbine
There are some self-defense trainers who believe that the carbine is not suited for home or personal defense, citing size and their belief that the carbine is ungainly. Others cite the expedient-development nature of threats, the notion that you won’t have time to get a long-gun in certain scenarios. I understand the ease of carrying and searching a structure with a pistol, but I’ve also conducted hundreds of narcotics search warrants and tactical operations searching for violent felons. My teammates and I chose to deploy with long-guns, either subguns or carbines, in these ops.

Further I’ve also been in self-defense situations at home when I had time to obtain and prepare my 5.56 carbine. One such situation occurred when my wife and I believed someone was shooting at our home from the woods behind our property (gunshots, then the sound of pellets whistling through the trees above the house). Prior to the local law enforcement response, it gave me comfort to know I could have taken a shot at a suspect 100 yards away in the wood-line.

No, to deal with violent criminals in today’s chaotic world requires a multifaceted approach. No one tool—not even a handgun—will suffice.

The M400 is based on customer feedback on what real-world people want to see in a 5.56 carbine. The M4 is making a comeback. SIG Sauer just made a simple and affordable rifle even better. That’s refreshing in today’s world. With proper training, practice and the correct mindset, the M400 can fill that self-protection niche with ergonomic handling, a sound design, lifesaving accuracy and dependable performance.



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  • skip clark

    Hey folks my name is skip from western pa. I just bought a sig 400 a few weeks agoand love it. As stated i went with sig solely on their reputation and price. Came with scope and sling in box for $489.00. The only problem i have had was with ammo feed.being new and using sub quality russian steel case ammo and thirity round clip i had a slight feed problem. Every thing being tight i had to recock the first 5-6 rounds to fire.after first 8 – 10 clips all setteled in and fed and fired fine. Other than that i love the weapon scope and price. By the way i am 64 yrs old a nam vet and gun smith . I have wanted an AR for some time and now have one i am very HAPPY WITH THANKS SIG keep up the good work skip clark

    • skip Clark

      Sorry folks i must correct the price was $ 849.00 new in box

    • kjhowler

      Say, skip…..i'm 63 and a VN vet also. My M16 was strapped to the back of my co-pilot's seat……happiness was a belt-fed weapon….starboard door.
      I avoided AR's for decades but just bought my first one also.
      Welcome home, brother…..we were galliant and did good….inspite of the media.

    • jerry

      hay skip
      were did you get a m-400 with a scope and sling for $489.00 please let me know merry chirstmas jerry

    • Ron Heywood

      I to am a NAM vet but was in the Navy.However I am am avid shooter but only have pistols. Have read so many positive reports on this Sig I want one. I live in the Winter Haven /Haines City Florida area and cannot find one within reasonable driving. Any help would be greatly appreciated.

      • Frank Rice

        Hey old timers. I’m one of you. 65 years old.I just ordered mine from a place called Element Arms in Big Lake Minnesota. I will get it Friday. My price was $855. That’s with the red dot Prismatic sight. We got a 6.5% state tax here so I’m not saying buy it from my dealer. Do a web search for Sig M400. You will find them all over the net. Watch out. They make a model that holds 10 for some states where that’s the max. Mine holds 30. By the way. It’s a 5.56 and not a .223. That’s good though. Shoots both 556 and 223. If you don’t understand look up the difference between guns 5.56 and .223. It has to do where the rifling twist starts in the barrel. .223 are no problem for a .556. You don’t want to shoot .556 through a .223. Bad things can happen.

    • Paul Harris

      Where did you get it at that price?

  • skip clark

    Thanks sig great weapon

  • sgtrovert

    I'm an FFL and sell mostly Sigs, as Ordnance Outsellers, I'm known for them. Previouly, Sig had pinned their LEO adoption hopes on 556: but since not "AR" departments didn't want to develop a new training syllabus! Personally, I'd prefer the 516 gas piston version: but with good maintainance the M400 will do fine. Personally, I'd take MOE version with great Magpul products that have great forend mounting flexibility without awkward balance and weight of some quadrail forends. MOE should also cost less than, or equal to quadrail, making it not much more than "standard". Reviewer didn't comment: but IMHO the ITAC red dot supplied is garbage and guarantee, if it works, won't be for long! Sig should be embarassed to include such poor products with their quality guns!

    • Hady Saleh

      SGTROVERT. i was wondering if you could send me a privte email with your ffl info . i would rather purchase my ar from a fellow service member whether retired or otherwise..

      Just got back from our latest sandbox vacation
      and Thank You for all you Gentlemens' service

      SGT Saleh

  • burl

    nothing about accuracy.

  • sgtrovert

    Skip and Howler, welcome home from another "Nam vet! You two are just kids, as I'll be 70 in a month……actually just jealous!

  • Top Shot

    If this rifle is any indication of the quality, or lack of, of SIG products, then it will be my first and last purchase of their products. The included rear sight on the M400 Enhanced with Magpul stock is nothing but junk. It is a flip up sight that came from the factory with the mounting screw over-tightened and the threads pulled. I noticed the pulled threads when I removed the sight to install a scope. Something else to look closely at is the factory warranty. SIG used to include a lifetime warranty on at least some of their products. The manual that came with this rifle had the Lifetime Warranty info on the back cover, but the included registration card was for a one year warranty. This won't be an issue for me, as I intend to have the M400 traded off long before the one year is up. Also, accuracy isn't bad, but for the money spent, should be better, especially with a 1:7 twist. You can get the same accuracy from a much cheaper rifle.

    • Bob-a-lu

      Funny, Mine came with a Limited Lifetime Firearms Warranty both in the Owners Manual and the Registration Card

      • sav

        Mine too.

        • Rick

          Mine too

  • Pa.Bill

    Another Vietnam Veteran here. I never liked M16's and why anyone would build a rifle that needed 'bolt assist' I never understood. I have SIG 556. Its a great rifle, no problems and eats all kinds of ammo. If the 400 is like the 556, you will find 5.56 xm855 green tip works the best.

    • jerry brown

      I'm a Sig dealer and love my 556! Sig 516 is gas piston gun and worth price difference over DI M400. Believe M400 is 1:7 twist, better with 62 grain+, while 1:9 better with 55 gr.j

  • Jim D

    I need some help, I just bought an M400 Sig sauer a couple weeks ago. The weapon does no have rear or front sight. The weapon has two rails and that is all. I have looked on the Sig web sight and online but cannot find any other models like it. Can someone tell me if I got ripper off or does Sig have a designation for a M400 With only two rails?

    • Jack M

      Hey Jim, I too bought one( at Wally World) in December and It is designated M400 SRP. has no front or rear sights but came with a Sig scope with selective levels of red or green lighting of the reticle. Had a nice fabric nylon case one 30 rd. mag and a sling that I haven't yet figured out how it attaches. Has no QD swivels at all. If you go to Sig's site and click on "Products" and then Riflws then M400 there are 9 variations. The SRP doesn't show any sights but mine had the Sig scope on it. Sme sort of package deal I believe. Jack

    • Jason

      Hey maybe we can trade guns, send pics to and I will do the same with mine. Then we can talk from there sounds like ya got a older models.
      Let me know either way, I want mine scoped.

  • Gatormark

    I hunt hogs,deer and coyotes with this 223 sig and it just keeps on surprising me, quality all the way. Accuracy? I flatened a 200 lb boar hog with this thing sat morning shooting 60 gr part ammo, its stoned him in place, no kick,squeal ,nothing, dead. This rifle is light,easy to carry compared to my 270 and cheaper to shoot. Super for tree stand hunting. Im not a vet, never owned a 223 platform( sold my mini 30 to get this rifle) but it may be the best,all around rifle I have hunted with. Got at wally world for 90 bones, money well spent.

  • Jason

    $90 bucks, Wow!!!
    Anyone that wants to sell a 223, 5.56, 7.62;39, please text me, email or facebook damn it.

  • Buddy

    90 bones???? Try more like 900 on black friday special last year

  • jeb

    SRP means Sight Ready Platform meaning you have to put your own sights on.

  • carlos the Great

    bought my M400 with rubber stock sold as a pistol on jan 29 at Gander Mtn. It cost 1389.00 no scope no sling only had the front and rear sights. My question is …why is it called a pistol instead of a carbine rifle ( ar15 platform) can I just ad the rear stock?

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