At SHOT Show 2010, SIG showed their new Model 516 and 716 rifles to the industry. The 516, a short stroke tappet version of the M4 was released to compete in the military and law enforcement markets both world wide as well as the U.S. With the direct gas versus piston operated controversy, SIG decided everyone is making a direct gas gun, why not then make a high quality piston operated rifle to satisfy those who have the piston bug. The 5.56mm SIG 516 is an M4 carbine with the only major differences being the operating system. The 516 is a very high quality manufactured rifle, which one would come to expect from SIG. Both the 516 and 716 are offered in selective fire variations along with several different barrel options.
The 716 is basically an AR-10-type rifle in most every way with the exception of the gas system. It contains many of the modern high paced modifications that the new high speed M4’s have.
The rifle is manufactured from the standard 7075 T6 grade aircraft aluminum, same as the Mil-Spec M4. The lower receiver is similar to that of an AR-10 with some modifications. There are two quick detachable mounting points on the rear of the receiver. There is also a spring loaded tension plunger under the takedown lever. This gives upward tension on the upper receiver tightening up the receiver’s so there is no play or rattle. The pistol grip is the high speed Magpul MIAD, which offers the shooter their choice of backstraps to compensate for hand size as well as the option for a front finger groove or a smooth front strap. There are also options for inserts into the grip that can carry everything from spare optic batteries to a spare bolt and firing pin. Depending on the model, the rifle can be had in either semiautomatic only or selective fire. The model 716 provided is a commercial/LE semiautomatic only. The trigger is a standard trigger, which is more than suitable for any target, personal protection or LE purpose. The magazine release button is ambidextrous. The left side has a button that is pushed and lifts the mag release to release the magazine. This is a feature that can be useful whether you are left handed or not. There are gripping grooves on the front of the magazine well.
The receiver extension has six positions and, as per Mil-Spec, has the receiver extension nut staked in place. The buffer/action spring is noteworthy in the fact that it uses a stronger flat spring rather than the standard round/rocket wire spring. The stock chosen is the Magpul ACS stock. This high speed stock has two battery/storage compartments that can be accessed from the rear of the stock. There is a locking lever that prevents unintentional movement of the stock. There is a smooth triangular shape to the cheek weld that is very comfortable. There is a storage compartment on the right side. The stock comes with a reversible QD adapter that can be placed on either side of the stock.
Although early prototype rifles used the ArmaLite modified M14 magazine, the final production magazine is the standard AR-10-type magazine. This rifle was provided with a 20-round Magpul PMag 20LR. However both the C-Products and the Knights Armament 20-round magazines are used with 100% reliability.
The upper receiver has a forward bolt assist as well as a fired cartridge case deflector. The flat top upper receiver has a Mil-Std 1913 rail on it. The handguard is removable with the turn of some screws. The quad Mil-Std 1913 handguard has four QD attachment points on them.
The bolt carrier is machined from a single piece of steel. You can visibly see where material has been removed to decrease weight. A standard AR-10-type bolt is used as well as extractor, firing pin and firing pin retainer pin. There are gas rings on the bolt but their only purpose is to make assembly easier. They are not needed for any mechanical reason.
The operating system is a standard short stroke push rod gas system. The regulator is removed from the front of the gas block by depressing a plunger and rotating the regulator and pulling it out. The regulator has four positions which are normal fire, adverse conditions, suppressed and gas shut off. The adverse condition setting should only be used when necessary and switched as soon as the weapon is cleaned. The operating rod contains the piston as well as the return spring.
The barrel is hammer forged and chrome lined giving an 8- to 10,000-round barrel life. The rifling is a 1 turn in 10 inch right hand twist. There are extended feed ramps both on the barrel extension as well as the upper receiver. The rifle comes standard with a M16A2/M4 compensator with the bottom remaining solid.
The cycle of operation for the SIG 716 is as follows: When the trigger is pressed the hammer strikes the firing pin that strikes the primer. The spark is created that ignites the propellant in the cartridge. As the propellant burns high pressure gas expands forcing the bullet down the barrel. When the bullet passes by the gas port, high pressure gas is bled into the gas port. Gas expands between the back of the gas regulator and the face of the piston. The gas pushes the piston/operating rod rearward making the operating rod move rearward and strike the bolt carrier sending the bolt carrier rearward. As the carrier moves rearward the return spring returns the operating rod/piston to its former position. As the bolt carrier moves rearward the bolt unlocks, extracts and ejects the fired cartridge case. When the carrier reaches it rear most position, the buffer spring returns the carrier forward where the bolt picks up a round from the magazine, chambers and the bolt locks in place ready for the next shot. The cycle rate of fire of the SIG 716 is 550 to 650 rounds per minute, which is relatively slow making this rifle very controllable on automatic fire. This also increases reliability enabling more time for the cartridge case to contract before extraction takes place.
For test firing the AimPoint Comp 4s was chosen for the optic. The Original Comp 4 was standard issue for the U.S. Army for many years. A few years back there was an upgrade. By request, the AA battery compartment/power knob was changed from the top of the right side to the bottom of the right side and hence the 4s. The battery life is up to 80,000 hours with 16 different brightness settings. The dot is 2 MOA in diameter. There are 7 different night vision devise settings with no eye relief. The 30mm optic is submersible in up to 25 meters of water. The Comp 4s came with some very nice lens caps. The rear is just a standard flip up lens cap. The front has a two piece flip cover. The primary is to protect the lens. That is lifted and the next cover has the anti reflective honey comb cover. You can snap the outer cover back on to the anti reflective lens cover and lift both and you have the bare optic. Many options are available. Many optics are powered by the CR123 as well as the CR2032 batteries. The problem is that they are not readily available. The AA battery is common everywhere in the world so it only makes sense that the AA is the better way to go.
The rifle was function tested with 500 rounds of Silver State Armory 7.62x51mm 147 grain FMJ (SSA10084-147FMJ). There were no malfunctions noted during any of the function testing proving the rifle to be accurate and reliable. All three types of magazines were used extensively. The rifle was not cleaned or lubricated during function testing. For Accuracy testing Silver State Armory 7.62x51mm 168 (SSA10084-OTM) and 175 (SSA10084-M118LR) grain OTM ammunition was used. The rifle shot consistent 1 to 1.5 inch groups at 100 yards.
Overall, this author thinks SIG has a winner. This rifle will compete with the LWRC REPR, H&K 417 as well as the POF piston operated rifles. Also the Colt CM901 if it ever sees production. There are relatively few companies who make this rifle so competition is minimal. SIG has the most competitive prices for a rifle of this type. As the debate will continue over direct gas or piston operated systems, there are companies who will provide the customer with what they want for whatever side of the fence you are on. The SIG 716 will serve any application asked of it whether it be service rifle, law enforcement rifle, hunting, personal protection or target shooting.