|Type / action||gas operated, semi-automatic|
|Caliber(s)||.223 Remington / 5.56×45 mm|
|Weight unloaded||3.6 kg / 7.92 lbs|
|Length||832 – 914 mm / 32.75" – 36"|
|Barrel length||410 mm / 16.125"|
|Magazine capacity||30 rounds|
Ruger SR-556 semi-automatic rifle is the most recent product of the famous American arms-making company Sturm, Ruger & Co. Ruger company previously manufactured 5.56mm / .223 caliber semi-automatic Mini-14 rifles, which were known for excellent durability and reliability, but the SR-556 is the first step of this company into the one of most lucrative segments of American rifle market, the "Ar-15 niche". Following the general trend, Ruger, however, developed an improved version of the basic weapon that has many factory-standard features which, otherwise, are considered as expensive aftermarket options. Most important of these features are short-stroke piston-operated gas action (as opposed to original direct impingement gas action of the classic Ar-15 rifles), cold-hammer forged barrel with flash hider, as well as quad-rail forend, folding detachable iron sights and quality 30-round magazines. This rifle is obviously intended for civilian and law enforcement markets.
Ruger SR-556 semi-automatic rifle utilizes gas-operated action with short-stroke gas piston, located in the gas block above the barrel. The piston is linked to the bolt group through the separate push rod that runs inside the handguards and has its own return spring. Gas system features manual gas regulator with 4 positions, from "0" (gas system shut off for manual cycling) through "3" (for firing when rifle is heavily fouled up or when using relatively low-power ammunition). Normal gas regulator position is "2". Gas piston and gas regulator plug are chrome-lined. Bolt group is similar in design to the standard Ar-15 bolt group except that instead of the gas key it has a lug which interacts with the pusher rod. The bolt, bolt carrier ad barrel bore are chrome lined as well. Combined with gas-piston system that keeps powder residue out of the bolt group and receiver, this will result in enhanced reliability over prolonged firing sessions. The upper and lower receivers are made from aluminum alloy and connected via traditional cross-pins. All controls (manual safety, bolt stop release, magazine release, cocking handle, bolt forward assist) are of typical Ar-15 pattern. Feed is from standard M16 / Ar-15 type magazines, and as of now each rifle is shipped from factory with three 30-round polymer PMag magazines. Standard furniture includes quad-rail forend (supplied by Troy Industries), Hogue pistol grip and M4-type collapsible buttstock with 6 positions. Standard sights, as shipped by factory, include Troy industries iron sights on folding bases, with flip-up diopter type rear sight, adjustable for windage, and protected front sight, adjustable for height. Top of receiver features integral Picatinny rail, so any type of red-dot or telescopic sight can be fitted using appropriate mountings.