By Guy Sagi

It’s not the most classic rifle in my gun safe, nor does it have a long family history like many of my other firearms, but if the apocalypse is knocking at the door, my SIG Sauer M400 will be the first thing I pull out and the last thing I surrender.

I really enjoy long-distance shooting and my collection reflects that passion. Don’t get me wrong. I’m good, but not an accomplished benchrest shooter or former military sniper. My made-for-radio face means I’ve never played either on TV, either. It’s the physics involved that attracts me, and on those occasions I do the math right and dope the wind properly at distance, it’s a feeling that’s hard to beat.

With the six-position adjustable buttstock fully extended, overall length of the M400 is 35 ¾ inches.

With the six-position adjustable buttstock fully extended, overall length of the M400 is 35 ¾ inches.

The six-position adjustable buttstock can collapse overall length to as short as 32 3/8 inches, and that ability to change that position ensures a good cheek weld, whether you’re stuck in a thick parka, or T-shirt.

The six-position adjustable buttstock can collapse overall length to as short as 32 3/8 inches, and that ability to change that position ensures a good cheek weld, whether you’re stuck in a thick parka, or T-shirt.

However, when we’re talking about a fast gun that never fails to run in a pinch, regardless of the circumstances, it’s hard to beat an AR-15. Its method of operation has a track record of performing in less-than-ideal conditions for the past 50 years, and it’s capable of stopping a criminal attack anywhere inside 300 meters. That makes the Sig Sauer M400 more versatile than my handgun—when concealment isn’t a concern—and its semi-automatic operation is a decided advantage over tack-driving bolt guns if things get “scary close.”

Fire controls are on the left side of the lower receiver.

Fire controls are on the left side of the lower receiver.

I purchased this M400 when SIG Sauer first introduced them on the market, so you may notice it has the discontinued carry handle. Its milquetoast appearance can be a turnoff to shooters on a budget and probably the reason it is no longer available.

If you, too, think it’s a little homely, then removal is as simple as turning a pair of bolts. The flattop receiver can then accept your choice of optic, although expect to go a little high on the mounts with the A2 front sight.

The carry handle is easily removed from the flattop upper receiver by loosening two bolts.

The carry handle is easily removed from the flattop upper receiver by loosening two bolts.

I kept the sights stock for a simple reason. Every gun should fill a specific role—even if it’s just for plinking—and this carbine is perfect for a home-defense or bugout centerfire carbine. These iron sights avoid the point-of-impact-changing dents, dings and bumps common in an emergency, thanks to the metal “wings” on both sides. That ruggedness is one reason A2 sights appeared on the first M16s in Vietnam. Their batteries don’t fail, you don’t have to turn them on and with a two-position adjustable rear sight, dialing down to a finer sight picture makes things a little easier at distance.

A whole new generation of shooters who have learned behind crosshairs and red dots may disagree, but I also think they’re a lot faster. Holographic sights may allow you to get a little sloppy in cheek weld and still deliver an accurate shot, but with enough practice, shouldering and sighting with irons is lighting quick. When a druggie attempted to invade my home 20 months ago, I didn’t even have to think about bringing the M400 on target—it was just there, intuitively. No shots were fired, the perp was caught and the nimble little carbine instantly earned a permanent place of distinction in my safe.

The rear sight is well protected in the carry handle, and it’s adjustable for a small diameter (longer, precise shots) and a wider one for fast, CQB-style work.

The rear sight is well protected in the carry handle, and it’s adjustable for a small diameter (longer, precise shots) and a wider one for fast, CQB-style work.

Of course, that means minute of angle at 300 yards isn’t where this 16-inch barrel and setup shines. Sub-two-minute performance at 100 is common, though, and it’ll do the same at further distances when I’m having a good day.

The rear sight is both windage and elevation adjustable.

The rear sight is both windage and elevation adjustable.

A quad-railed forend was the only change made to this M400, largely because of family requests. Metal inserts in the SIG Sauer handguard doubly shield the shooter from barrel heat, so if it wasn’t for the priority of adding a pressure-activated weaponlight, the gun would have stayed stock.

A standard charging handle is used on the M400.

A standard charging handle is used on the M400.

A forward assist will come in handy in an emergency if the AR-15 will be used for small game hunting.

A forward assist will come in handy in an emergency if the AR-15 will be used for small game hunting.

This carbine was SIG’s first foray into a direct-gas-impingement AR-15, and the company did things right. About the only complaint I have is a non-ambidextrous safety on a gun with magazine releases on both sides. That’s minor, though.

The M400 has some subtle refinements that are rare on many of today’s AR-15s. Generous flaring on the mag well ensures fast reloads—an important advantage when fine motor skills diminish under stress. I’ve yet to uncover a magazine it won’t run flawlessly.

The carbine’s flared magazine well ensure fast and reliable reloads.

The carbine’s flared magazine well ensure fast and reliable reloads.

A six-position, adjustable stock allows overall length to vary between 35 ¾ inches to 32 3/8, ensuring proper fit for shooters of various arm lengths. It also means you can find a good cheek weld, even on blustery days at the range when a heavy coat is necessary. A sling-attachment point is at the heel of the buttpad, but there’s also a QD mount on the back, right side of the lower receiver. The front-mounting position is under the A2 front sight. There is no sling on my M400. They have a tendency to hang up on door handles and other objects when you’re in a hurry, and in an emergency, I don’t need something else going wrong.

A six-position adjustable stock provides for a proper cheek weld whether you’re in a T-shirt or heavy parka.

A six-position adjustable stock provides for a proper cheek weld whether you’re in a T-shirt or heavy parka.

A sling can be mounted at the bottom of the stock’s buttpad, but there’s also a QD mount at the back of the receiver for that purpose.

A sling can be mounted at the bottom of the stock’s buttpad, but there’s also a QD mount at the back of the receiver for that purpose.

Trigger let-off weight is consistent at 5 pounds. There’s some take up, but nothing compared to a lot of AR-15s I’ve tested. If you shoot the reset on your guns, when possible, you’ll like the way it feels and runs on an M400. It’s palpable enough that two of my grandsons learned the technique on this carbine—fast.

The carbine comes with a trigger that’s pretty much stock for an AR-15, but it’s let-off weight is a smooth and consistent five pounds, and the palpable reset makes accurate follow-up shots quick and easy.

The carbine comes with a trigger that’s pretty much stock for an AR-15, but it’s let-off weight is a smooth and consistent five pounds, and the palpable reset makes accurate follow-up shots quick and easy.

It’s also the firearm the entire family wants to shoot. Recoil is minimal and it fits everyone. Even the left handers don’t complain about the fire-control location, although they learned the magazine-release location fast. You never know if you’re going to be the one “on scene” when an apocalypse strikes, so the ability of loved ones to run it well is yet another reason this rifle isn’t going anywhere.

Fire controls are on the left side of the receiver, for righties, but the other side provides a good visual indication of the firearm’s status for other shooters.

Fire controls are on the left side of the receiver, for righties, but the other side provides a good visual indication of the firearm’s status for other shooters.

An ambidextrous magazine release on the M400 is a nice touch, with it located just below the bolt release on the lower receiver’s left side.

An ambidextrous magazine release on the M400 is a nice touch, with it located just below the bolt release on the lower receiver’s left side.

The front and rear sights are elevation adjustable, with windage corrections also made at the rear. An A2-style flash hider rides the barrel up front, protecting the threads until I decide another muzzle device is in order. Right now, I’m satisfied.

The A2-style post sight up front is elevation adjustable and well protected by metal “wings.”

The A2-style post sight up front is elevation adjustable and well protected by metal “wings.”

An A2 flash hider tops the 16-inch barrel.

An A2 flash hider tops the 16-inch barrel.

The only thing altered on this M400 is that quad-railed forend, which speaks well for the gun as it rolled off SIG Sauer’s assembly line. It’s yet another reason this reliable—and nimble at 6 pounds, 7 ounces—home-defense gun is staying the way it is, and in my safe.