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SIG Sauer M400 Review

SIG Sauer M400 Review


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.

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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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