A few years ago I had the opportunity to attend SIG Sauer's Academy and take the Defensive Rifle Course. While there I had the opportunity to shoot one of SIG's 550 series select fire assault rifles. I loved that weapon and I wanted one. Unfortunately, they were only available to military and law enforcement agencies, so my desire to own one went unfulfilled.
But the staff assured me that SIG was working on making the 550 family available to the public and to individual officers for purchase. The plan was for SIG's new rifle to be called the 556. It would use AR-15 magazines, keep the SIG 550 look, and, to make it available to the public, it would be semi-automatic. Best of all, it would retain the two-position gas adjustable gas piston, ensuring reliability under the worst of conditions.
When SIG started marketing the 556, it sold like there was a buy-one-get-one-free sale on the things. This meant editorial samples of the 556 were limited, and it was nearly a year after sales to the public started that one was available for test and evaluation. Ever since it arrived months ago for testing, I've been putting the 556 SWAT SIG through its paces. The rifle has been everything I hoped for.
Duty Ready
The 556 is a duty-ready rifle built to accept various optics, lights, other aiming devices, and vertical forearms; it even ships with SIG's Grip-Light.
Unlike other "black guns," which are gas operated, the 556 is piston driven. The piston system reduces the fouling of the bolt and the associated moving parts. The gas tube vents gas through the numerous ports before the piston drives the rotating bolt. This venting is what reduces dirt, and ultimately reduces cleaning time. Should the system get dirty, the two-position adjustable gas piston of the 556 ensures that it will run in the worst of conditions.
SIG uses a 16-inch cold hammer forged barrel with one-in-seven twist rate on the 556 to stabilize a wide variety of bullet weights. As an added bonus, the company makes its own barrels, so it can maintain quality control throughout the manufacturing process. Mated to the barrel is SIG's flash suppressor, which does a superior job reducing the flash signature of the 556. The flash suppressor has an ACME-type thread, so it will mate with select sound suppressors.
The barrel is threaded to a high carbon steel upper receiver, which is Nitron coated to ensure the receiver is corrosion resistant. This ensures a solid shooting platform capable of handling the hottest rounds while enhancing the accuracy of the rifle. To facilitate the installation of optics, the receiver is a "flat top" Picatinny rail with a built-in, hidden rear sight. This sight is not designed to be a primary sight; it is purely a backup in the event your optics go down.
The rifle's charging handle and bolt are contained in the upper receiver. There is no dust cover over the receiver; SIG opts to use a slotted rubber cover to keep out debris. It appears to me that the system works well. I say this because I haven't noticed any "stuff" in my receiver.
The upper receiver is mated to the lower using a rear push pin and slotted front pivot pin. There is no play between the receivers and the seam is flush and smooth.
As on many other black guns, the lower receiver of the 556 is CNC machined aluminum, which is hard coat anodized. The ambidextrous safety and magazine release are located on the lower receiver as they are on an AR-15. The bolt release is behind the magazine well above the trigger and is pushed down to lock the bolt up to release it.
A major design change for the 556 over other 550 series rifles is the magazine. The 550 used proprietary magazines, which are in limited supply. SIG redesigned the 556 to accept AR-15 magazines, giving operators a large and affordable supply of magazines. The mag well on the 556 is larger than ARs, assisting in smoother, faster reloads.
The forearm is a vented aluminum quad rail. Venting the front rail reduces heat build-up and reduces the weight of the 556.
To protect the Picatinny rails, SIG includes snap-on polymer rail covers. The railed forearm and receiver are level, allowing optics to mate with magnifiers and night vision devices.
SIG ships the SWAT 556 with its Grip-Light. This is a vertical grip with a removable high intensity LED STL 100 light. There is a trigger to activate the light, and it can be locked out so you won't inadvertently activate the light.
While the 556 doesn't use a buffer tube assembly common to ARs, it was designed to accept AR stocks. SIG installs a Magpul CTR on the 556. This is a five-position stock that can be locked in place, which reduces the chances of the stock accidentally collapsing and eliminates the wobble of adjustable stocks.
The 556 was finished in all black with SIG's Nitron finish or hard anodizing. Both finishes were smooth and even on all parts. The finish on the 556 will help ensure your carbine does not corrode and can be easily cleaned.
Adding Optics
Before I took the 556 to the range, I made a few changes. First, I removed the Grip-Light and installed a Wilcox Industries Steady Grip with bipod. I prefer this grip because it gives me a quickly deployable bipod and adds very little weight to the weapon. This bipod is very stable and is what I planned to shoot the 556 from when testing its accuracy.
I also wanted my 556 to have optics that could function for multiple missions. For this reason, I chose Leupold's Mark IV CQ/T. The CQ/T is a variable power scope with a magnification range of one to three power. This scope has a dot for fast acquisitions at close-quarter-battle distances and magnification when accuracy is required. The CQ/T also has an electronic amber dot for low-light applications. Best of all, the scope is powered by easy to find, inexpensive AA batteries.
To mount the CQ/T, I chose to use A.R.M.S. Inc.'s #12 mount. This mount lets me rapidly remove the CQ/T to use the backup sights or to install a more powerful telescopic sight should I need to make a more precise shot. The A.R.M.S. mount is rock solid and does not require you to confirm your sight's zero when you replace it.
Last, I contacted Magpul to acquire the rubber butt pad and cheek riser for the CTR Stock. The riser ensures proper eye-to-scope alignment and the rubber butt pad reduces the slipping of the stock during sustained firing.