The author takes a look at a world-class AR pistol well-suited for home defense in this SIG P516 review.
The weapon you choose to defend your home must be maneuverable, compact, simple to use for you and your household members, and it must provide the necessary firepower to stop an intruder. AR pistols are just that type of weapon for home defense, and the SIG P516 pistol with the SB15 Pistol Stabilizing Brace is the type of weapon designed for close-range maneuvering. The SIG P516 has a hard earned reputation among military and law enforcement personnel in the U.S. and around the world as a reliable, capable firearm.
The P516 is based off the SIG 516 rifle, which is built on an AR-15-type platform with a refined operating system that is combat-reliable. Instead of the traditional direct-impingement gas system found on a standard AR-type platform, the 516 series—both the rifle and the pistol—use a short-stroke, gas-piston/pushrod operating system. This piston system ensures that carbon fouling and excess heat never reach the chamber or bolt carrier.
In turn, this significantly improves the weapon’s functionality. There is minimal heat to dry out oil or gunk from burning gases.
All About That Gas
This operating system also uses a four-position gas valve that allows a user to adjust the gas in one of four positions. Position No. 1 provides normal gas flow to operate the P516. Position No. 2 allows extra gas flow for adverse situations, such as when the weapon is fouled and short stroking. Position No. 3 reduces gas flow to enhance suppressor use, and position No. 4 turns off the gas value for optimized suppression and makes the P516 function as a single-shot pistol. Most users will keep the gas value in position No. 1, but it is useful that SIG’s engineers allowed the value to be adjusted for numerous scenarios and circumstances. Practically useful, the valve can also be adjusted using the tip of a cartridge.
When it comes down to it, an AR pistol is a compromise that spans the gap between a typical 16-inch-barreled AR-type rifle and an AR-type Short Barreled Rifle (SBR). The difference between the 16-inch AR-type variant and the SBR, other than the barrel length, is the paperwork required to legally own an SBR. This includes an ATF Form 1, local law enforcement approval and the purchase of a $200 tax stamp. The “AR pistol” designation allows gun owners to avoid the additional paperwork while maintaining a shorter barrel. The compromise, of course, is the absence of a butt stock. The solution to that problem, if you can call it that, is the SB15 brace. The SIG P516 with the SB15 brace makes the pistol easier to control. It’s certainly not the rock-steady hold of a butt stock, but it’s steadier than the typical handgun hold.
The P516 is built with forged 7075-T6 aluminum upper and lower receivers with a hard coat anodized finish. The upper features a free-floated, military-grade, nitride-treated, 10-inch barrel with a twist rate of 1:7 inches with six grooves. At the muzzle is an A2-style flash hider. When decreasing the length of barrel in the AR-type platform, having adequate gas to operate the system is an engineering challenge. After speaking with a SIG spokesperson, they agreed it was a challenge, and that is why the short-stroke system is used.
“The P516 requires a bit more gas than the SIG 516 to run reliably since there is less recoil mitigation when compared to a stocked rifle,” according to SIG. “So the gas port is larger on the P516, and since it enhances reliability on SBRs, the SIG 516 SBR also runs the same gas port.”
SIG’s short-stroke gas pushrod system also makes SBRs and P516s run more reliably than a direct-impingement gun. This becomes magnified once the barrels become 11 inches or shorter. So, if you’re looking for the most reliability out of a SBR or an AR pistol, you really should be looking at a short-stroke gas pushrod system.
The barrel and the short-stroke piston system are then sheathed in an aluminum quad-rail handguard. The quad rail allows a user to mount accessories, and in the case of a homeowner there is plenty of rail space for a tactical light. Ergo rubber rail covers are included with the pistol, so the unused quad rails are more comfortable to hold and less abrasive. The topside is a true 1913 Picatinny rail that runs from the very rear of the upper to the adjustable gas valve, giving the user plenty of mounting options for optics.
A red dot or reflex sight is a natural choice for close-up work in a room or down a hallway. Adjustable flip-up iron sights snap upright into position, then fold back away from the muzzle. They deploy in seconds. The rear sight offers two aperture sizes and is adjustable for windage, while the front post sight is protected by wings and is adjustable for elevation. I found the iron sights perfectly adjusted for 25 yards. I mounted a Mepro Tru-Dot RDS with a 1.8 MOA red dot reticle, which offers rapid target acquisition with both eyes open through a large viewing window. The RDS is a commercial version of similar sights used by Israeli Defense Forces.
Constructed with an aluminum body and tough polymer frame, the RDS runs on a single AA battery, providing thousands of operating hours, plus it features an automatic shut off to conserve power. The reticle has four brightness settings: three for day/night use and one for use with night vision gear and magnifiers. The unit features an integral Picatinny rail mount with QD levers, and when mounted, it perfectly co-witnesses with the flip-up iron sights. At 10.5 ounces, it is lightweight and only takes up 4.5 inches of rail space.
The lowers on the SIG 516, SIG 516 SBR and P516 are identical. There is no difference other than the lack of stock on the pistol. The P516 features an ambidextrous selector and magazine release, making the P516 more versatile and faster to operate regardless of whether you are right- or left-handed. The Phase 5 extension tube is fitted with SIG’s SB15 pistol stabilizing brace. The brace is shaped like a clamp and made of a rigid yet flexible rubber similar to that used in swim fins and diving mask material. The operator’s shooting arm is inserted into the brace, and an attached hook-and-loop strap secures the weapon to the user’s forearm. A second strap can also be used to more securely attach the weapon to the shooter’s arm. The brace is easily removed or installed by pulling it off or sliding it onto the buffer tube. The SIG P516 can be used with or without the brace.
The pistol grip is SIG’s proprietary pistol grip with an ample texture and an arched backstrap. It is very comfortable to hold. The single-stage trigger pull measured on average 7.6 pounds but felt lighter. There was a slightly perceptible bit of creep but not enough to interfere. This is a defense weapon, after all, and not a target pistol.
At the range, my assumption was that the P516 would not be as accurate as a typical 16-inch barrel variant. I was wrong. Using a rest, I was able to average ½-inch groups or better at 25 yards with five shots using 55-, 62- and 77-grain ammo. The P516 is a shooter. It particularly liked the new Norma USA 77-grain Sierra MK HPBT ammo and the new Barnes VOR-TX all-copper 55-grain TSX FS bullet. Even the economical Fiocchi 55-grain FMJ BT performed well.
The new HPR Black Ops OTF uses a 62-grain Open Tip Frangible bullet that is specifically designed for home defense and offers less over penetration. Going to off-hand shooting, I found the brace helped provide more stable shooting. Don’t get me wrong, this is a pistol with a 10-inch barrel that weighs 6.5 pounds, and holding at arms length gets tiring fast. Firing for speed from the hip, the SB15 brace kept the P516 steady.
Removing the SB15 brace, I also attached a Blackhawk one-point Storm Sling to the P516 via a Magpul QDM sling swivel. The P516 has a built-in sling-swivel mount on each side of the lower. With the sling over one shoulder and across my chest, I pushed the pistol out from my body, and the sling provided a more steady set up. Holding the P516 in two hands, the pistol was easy to manipulate and hold steady. I liked shooting the P516 with both the red dot and iron sights. With either the SB15 brace or a one-point sling, you give yourself an edge with a more solid hold. With no snags and excellent accuracy, the P516 offers everything you need when picking up a weapon in haste to defend your home.
Other than the AR pistol itself, considerations for home defense include choosing the right ammunition and, where legal, a suppressor. Suppressors can greatly reduce the noise from discharged rounds in confined spaces, thus protecting your hearing. As always, it’s important to check the laws in your state and make the best decision for you and your family.
Caliber 5.56x45mm NATO/.223 Rem.
Barrel Length 10 in.
Overall Length 26.5 in. (with SB15 brace)
Weight Unloaded 6.5 lbs.
Grip SIG textured grip
Sights SIG adj. flip-up front/rear
Action Short stoke gas piston
Finish Matte black hard coat anodize
This article appeared in the Fall 2015 issue of Gun Digest the Magazine.
- Sig Sauer Pistols
- 516 Patrol Rifle
- M17 Civilian Variant
- MCX Rattler
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