There’s just something about AR-style pistols that interests a number of AR-15 enthusiasts, and that interest creates enough demand to spur some AR-15 manufacturers to produce them. The enthusiasm for the pistols could have something to do with the fact that although they are not easily carried, aimed or readily concealed, they can have a self-defense role in certain special situations. Whatever the reason, the demand has caused Sig Sauer to offer a pistol version of its highly successful and rugged AR-15 rifle. In 2010, Sig Sauer introduced the SIG516 piston-driven AR-15. It was the company’s first AR-style gun and was thoroughly tested for dependability. I witnessed an endurance demonstration where the gun was buried in sand, submerged in water and buried at the bottom of a pond in mud before being fired, all without a single malfunction; no cleaning or lubrication was required to keep it running. The pistol is of the same basic design and pedigree, so it should be a tough gun.

“Surrounding the SIG P516’s free-floating barrel and piston is a 7.25-inch-long handguard with Picatinny rails on all sides.”

Although a 7-inch barrel is offered, the pistol received for testing had a 10-inch barrel. That length is the same as one of Sig’s short-barreled rifles, but the pistol does not require ATF approval for civilian ownership. The barrel is chrome-lined and makes one twist in 7 inches, which is good for stabilizing longer, heavier bullets. It is finished with manganese phosphate for durability and corrosion resistance. Attached at the front is an A2-style birdcage flash suppressor that makes a pretty good attempt at reducing the flash signature, which is difficult with such a short barrel. A removable flip-up front sight is attached to the short Picatinny rail on top of the gas block. Inside the gas block is the gas valve (or plug) that connects to the piston, which sends the bolt carrier group to the rear, cycling the action. The plug can be rotated to one of four positions and features a round hole into which a cartridge can be inserted to help turn it.

When the valve is in the vertical position, the system is set for normal operation. Turning it one notch clockwise (when viewed from the rear) aligns a slightly larger hole in the gas valve with the gas port in the barrel to deliver a bit more power to cycle the gun. This is helpful if the gun is dirty and isn’t cycling optimally, since the shooter can’t really stop to clean it. Sig recommends not running the gun with the valve in this position for long because it puts extra wear and stress on parts. Turning the plug from the normal position counter-clockwise one notch aligns a smaller hole in the valve with the gas port, reducing the amount of power delivered to the piston and bolt carrier group. This position is used when a sound suppressor is attached. With a suppressor, there is more rearward pressure, and not as much gas is needed to run the gun. To move the plug to this position, a small plunger on the front of the gas block must be depressed.

If the gas plug is turned two clicks clockwise from the normal position (this also requires that the plunger be depressed), gas is prevented from entering the gas system, which keeps the bolt carrier group from cycling and brass from flying when a round is fired. This position is used to obtain the highest degree of sound suppression when using a suppressor. Some believe that this cut-off position also enhances accuracy, but the gun must be cycled by hand. The piston itself has three gas rings and fits snugly into the gas valve. One of the advantages of a gas piston system is that fouling and hot gas are not routed into the receiver, as is the case with a direct-gas-impingement gun. This reduces stress and heat on the bolt carrier group, allowing the gun to run without as much lubrication, and makes cleanup easier. The hot gas instead impacts the piston, so carbon builds up there instead of in the bolt carrier group. Wherever the carbon accumulates, though, it still needs to be removed periodically in order for the gun to keep running. Piston cleaning cannot be neglected. Surrounding the free-floating barrel and piston is a 7.25-inch-long handguard with Picatinny rails on all sides. Sig supplies ERGO ladder-type protective covers for the T-marked slots, of which there are plenty for mounting accessories. But do not put a vertical foregrip on this pistol—that’s a ticket to jail! The two side rails have quick-detach sling swivel sockets at the front and back for the attachment of a sling, and there are also sockets on each side of the lower receiver, just in front of the buffer tube. A sling is a very good idea on this pistol because a holster is pretty much out of the question and some convenient method of carrying it is needed. The upper receiver has a standard AR-15 appearance with a T-marked Picatinny rail running the length of it. At the rear, Sig supplies a removable flip-up iron sight with large and small apertures. The gun is also equipped with the standard charging handle, bolt forward assist and brass deflector; however, inside the upper receiver the bolt carrier group is decidedly not standard when compared to a direct-gas gun.

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The carrier does not have a gas key. Instead, it has a boss that is machined directly into the carrier where the gas key would otherwise be. The carrier is faceted, not round, and has lightening cuts. It is treated with what appears to be a black nitride finish instead of phosphate, and it is not chrome-lined because it doesn’t have to be. Also referred to as Melonite, the black nitride finish is extremely hard, durable and corrosion resistant. The rear of the carrier is also slightly larger than a direct-gas bolt carrier in order to fit inside the buffer tube more snuggly. This reduces carrier tilt, which is an unfortunate consequence of the change from a direct-gas to a gas-piston system. However, the modified carrier solves the tilt problem even if it does require that the rear of it (and the interior of the tube) be lubricated. The bolt looks like a direct-gas bolt, and the extractor is equipped with a black spring insert and a rubber ring to increase gripping power on the rim of spent cartridges.

The lower receiver looks similar to that of a typical AR. However, Sig has made some interesting changes. The fence surrounding the magazine release is larger and square instead of round. The magazine release is also ambidextrous. And, in order to make it easier for the operator to engage the bolt catch, Sig added an extension to it. The safety selector and trigger are typical for an AR, and the trigger on the test gun broke at a little more than 8 pounds after some take-up and a bit of overtravel. It’s not a match-grade trigger, but it’s not meant to be.

The magazine well is beveled to enhance fast reloads, and the gun is supplied with one 10-round magazine. The pistol grip is a Sig design that increases the size of the backstrap as compared to an A2 grip. This makes the trigger reach longer, which some people like. The grip is also textured on the sides and has ridges front and back to reduce slippage. It also has a trap door in the bottom so that spare parts or batteries can be stored inside. The buffer tube, or receiver extension, is heavily knurled for a short distance behind the receiver; beyond that it is smooth. At the rear is a raised portion with two flat sides that are apparently there to accept the jaws of a wrench for assembly and disassembly. This is not the standard buffer tube found on an AR rifle, so it will not accept a buttstock. Don’t attempt to put one on, or you will be violating the law.

Testing was conducted at the Scottsdale Gun Club’s indoor range, where the P516 attracted a lot of attention. During testing not a single malfunction was encountered. From a benchrest, the gun proved to be very accurate, with groups averaging about an inch or less using an EOTech XPS3 red-dot sight. That is much better accuracy than the average person can expect to get out of a typical handgun. In off-hand shooting, the gun is a handful. But any AR-style pistol is going to be. All are front heavy and weigh more than most handguns, so they are hard to hold steady. There are several ways to grip them, and the owner will have to experiment to find his preferred method. One way is to hold the pistol grip in the normal manner with the support hand wrapped around the firing hand in a Weaver or isosceles stance. Another is to grasp the handguard with the support hand, which I found to be much more usable. Others will hold the magazine well with the support hand, which is an acceptable alternative.

A major aid to aiming and handling one of the P516 is Sig’s SB15 Pistol Stabilizing Brace, which is designed to slip over the buffer tube and help steady the aim. Once installed, the shooter slips his forearm through the brace, grasps the pistol grip and cinches the retaining strap tight. The Stabilizing Brace may look something like a buttstock, but it is not adjustable for length, it is made of flexible polymer so it is not solid like a buttstock, and it is pretty short. Sig sells it specifically for attaching to the shooter’s forearm to stabilize the gun when using a one-handed stance. And it works!

Users could also opt for an adjustable sling, which, when wrapped around the back or shoulder can be stretched tightly. The rearward tension against forward pressure helps to steady the gun. And, with a sling, a person can carry the Sig P516 discreetly underneath a long coat, making the gun a sort of personal defense weapon along the lines of a short-barreled rifle. However, a lot of practice would be needed to develop the skills necessary to effectively use this weapon. On the other hand, the gun is fun to shoot and a bit of a novelty. If you want to attract attention at the range, or just want to try something different, the Sig P516 pistol is a gun to consider.

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For more information on the Sig Sauer P516 5.56mm AR-Style Pistol, visit or call 603-772-2302.

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