SIG SG 516

The SIG516 is a firearm manufactured by SIG SAUER. The rifle is based on the earlier 5.56mm AR-15 and M16.

Operating mechanism
The SIG516 is a semi-automatic firearm multi caliber rifle, intended for civilian and law enforcement markets. The same family also includes selective-fired "assault rifles", strictly intended for law enforcement and military use. 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. This is used to maintain reliability in all environmental and adverse conditions, or with suppressors and 40mm applications

Features
Ergonomically, the SG 516 is patterned after the AR15 type rifle. It 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. 516 models are equipped with an M16-A2 style bird-cage flash hider.

All SG 516 models except the Marksman are equipped with 16 inch barrels shrouded by a free-floating M1913 Picatinny rail, as well as flip up iron sights (BUIS) made by SIG Sauer.

The 5.56x45 NATO SG 516 models accept AR15 style box magazines. These magazines are constructed in 5, 10, 20, and 30 round variants. SG 516 Russian rifles must use a different magazine, as they are chambered in 7.62x39. The SG 516 Russian uses magazines designed for 7.62x39 AR15 rifles. The rifle is hammer-fired and has a 2-stage trigger mechanism in the SG 516 Marksman, while all others have a military spec single stage trigger.

A bolt hold-open device locks the bolt carrier assembly open after expending the last cartridge from the magazine and is released by pushing the bolt catch lever located on the left side of the receiver. Alternatively, a left-handed shooter may release the bolt by pulling the charging handle to rear a short distance.

The SG 516 has a telescoping skeletonized buttstock. The ACE-style stock moves forward and rearward in 6 positions. A spring loaded release underneath the buffer tube area locks into each position automatically. The upper receiver, lower receiver and handguards are made from aluminum. The 516 Patrol comes in black, while the 516 Patrol FDE and SG 516 OD Green are Cerakoted in their respective colors.