SIG Sauer SIG516
The SIG Sauer SIG516 is a rifle manufactured by SIG Sauer. It is an AR-15 style rifle chambered in 5.56×45mm NATO. Introduced in 2010, the SIG516 was discontinued as of 2019 after the introduction of the SIG MCX. A variant chambered in 7.62x51mm NATO, the SIG716i, remains in production.

History
The SIG Sauer SIG516 shares lineage to the Heckler & Koch HK416. The principal firearms engineers for the SIG516 were Robert Hirt and Chris Sirois. Engineer Hirt was instrumental in the development of the HK416. Following his time with Heckler & Koch, Hirt was recruited by SIG Sauer to work with then SIG engineer Chris Sirois  on an improved version of the HK416. whilst omitted many proprietary HK416 components that were exchanged for standard (M4 carbine mil spec conform) components: the SIG516. Other HK416 issues like the (at the time) high cyclic rate, which causes lower life cycle. a gas vent, which showed up in low light conditions, and safety issues (i.e. the need for a firing pin safety) were also addressed. Hirt and Sirois later designed the SIG716 and SIG MCX/SIG MPX. They were later recruited by Caracal to develop a new rifle iteration that was superior to both the HK416 and SIG516 series. the CAR 816 series.

Design details

Operating mechanism

The SIG516 is a semi-automatic or select fire multi-caliber rifle. It fires from a closed bolt, and has a short-stroke push rod piston system. The gas piston pushes the bolt carrier rearward, where it is returned to the forward and locked position by a spring. This process loads the next cartridge. The 516 has a four-position gas regulator, allowing the user to choose the amount of gas directed to the piston, to adjust the gas system to function reliably with various propellant, projectile, fouling, operating environment and configuration specific pressure behavior.

Features
The SIG516 is based on the AR-15 platform ergonomic architecture, but uses a short-stroke gas piston operating system (unlike the AR-15's piston-operated gas impingement system). The 516 uses a proprietary belt carrier and government (law enforcement and military contract select-fire) rifles a special tungsten granules containing buffer to manage bolt carrier bounce and soften recoil. The barrel is chrome lined. The amount of movement between the upper and lower receiver is minimized by a rubber wedge.

The SIG516 has a safety lever on the left side, to be used by the thumb of the shooting hand. The gas block integrates an adjustable gas regulator. The front gas block is railed to accept the front sight with a flip-up sight post. SIG516 models are equipped with an M16A2 style bird-cage flash hider.

All SIG516 models except the Marksman are equipped with  barrels shrouded by a free-floating M1913 Picatinny rail, as well as flip-up iron sights (BUIS) made by SIG Sauer.

The 5.56×45mm NATO SIG516 models accept AR-15 style box magazines. These magazines are constructed in 5-, 10-, 20-, and 30-round variants. SIG516 Russian rifles use a different magazine, as they are chambered in 7.62×39mm. The SIG516 Russian uses magazines designed for 7.62×39mm AR-15 style rifles. The rifle is hammer-fired and has a two-stage trigger mechanism in the SIG516 Marksman, while all others have a military specification single-stage trigger.

It is built to pass the NATO test protocol “Over the Beach”, meaning the SIG516 is designed to fire safely as quickly as possible after being submerged in water.

Variants

SIG516 Precision Marksman
The SIG516 Precision Marksman has a longer  barrel and an adjustable 'sniper' stock. It weighs  and has a length of . The barrel is chrome-lined. Ion and or optical sights are  installed on an integral MIL-STD-1913 Picatinny rail on the top of the receiver and additional accessories can be mounted on the fore end quad rails.

SIG716

The SIG716 is a battle rifle variant, which is based on the same design, but is chambered for the larger 7.62x51mm NATO round and uses SR-25 pattern magazines.

SIG716 G2
The SIG716 G2 (Generation 2) variant features a short-stroke pushrod gas system. This operating system reduces carbon fouling, excessive heat and unburned powder in the action, ensuring further improved reliability and function. The G2 Patrol model is chambered in 7.62×51mm NATO, while the G2 DMR model is chambered in 6.5mm Creedmoor.

SIG 716i
The 716i (impingement) variant features a gas-operated, rotating bolt (internal piston) system instead of short-stroke pushrod gas system. This Stoner bolt and carrier piston operating system has helped SIG Sauer to bring down the cost of manufacturing and pushing more sales of 716i, whilst also achieving a weight reduction. The 716i is chambered in 7.62×51mm NATO. Sig Sauer appears to have discontinued SIG716 and SIG716 G2 models, since the company stopped displaying these products in their website, while they continue to sell magazines and spare parts in their online store. The 716i has been recognized as the best AR-10 rifle for the year 2020, by readers' choice voting of Ballistic magazine.

Users

 : Used by law enforcement.
 : Used by Canadian Special Operations Forces Command.
 : Used by Navy El-Sa'ka Forces.
 : In use with the Georgian MIA and MOD special forces
 : Used by the Hong Kong Police Force including the Special Duties Unit and the Counter Terrorism Response Unit.
 : Order placed for 72,400 units of SIG 716 g2 model. In December 2019, the first lot of 10,000 rifles was delivered to the Indian Army’s Northern Command. Sig Sauer also confirmed that delivery of the first order has already been completed. Another batch of 70,000 rifles was cleared for order in December 2023.
 Indian Army: 66,400 units in service. 70,000 on order
 Indian Air Force: 4,000 in service.
 Indian Navy: 2,000 in service.
: Used by the Mobile Brigade of the Indonesian National Police, SIG716 G2 used by Indonesian National Armed Forces special forces unit.
 : Transitioning into the general service rifle of the Naval Infantry Force.
 : Used by PTJ (Counter-Terrorist Unit) of Serbian Police
 : SIG516 and SIG716 variants used by Subunidad de Acciones Tácticas of Peruvian Police.
 : Used by the Mobilen Einsatzpolizei of the Aargau Police.
 : Used by Police Special Operation Department and Police Counter Attack Teams
 : Used by the SBU and GUR.
 : Used by Metropolitan Police Counter Terrorist Specialist Firearms Officers (CTSFO) Surrey Police and West Midlands Police
 : Used by Florida Highway Patrol when purchased in 2019, Delaware State Police when purchased in 2012 and also by Cincinnati Police Department SWAT, as well as the Anderson County, South Carolina Sheriff's Office SWAT. San Diego Police Department SWAT, in which the rifles will replace out aging Vietnam era M16s.

See also
 List of semi-automatic rifles

References

External links
 716i TREAD at sigsauer.com
 SIG716G2 PATROL at sigsauer.com
 SIG-Sauer 516 at modernfirearms.net
 SIG-Sauer 716 at modernfirearms.net

5.56 mm assault rifles
7.62×39mm assault rifles
SIG Sauer rifles
Assault rifles of the United States
Semi-automatic rifles of the United States
ArmaLite AR-10 derivatives
Weapons and ammunition introduced in 2010
Short stroke piston firearms