Ruger AR-556

The Ruger AR-556 is a semiautomatic AR-15 style rifle manufactured by U.S. firearms company Sturm, Ruger & Co. Introduced in 2014 as an entry-level AR-15 using a direct impingement action, with variants since being released such as the upgraded AR-556 MPR (multi-purpose rifle) in 2017 and the AR-556 pistol in 2019.

Overview
The standard model makes use of a traditional direct impingement with a 7 in carbine length gas system and has a cold hammer forged 4140 chrome-moly steel barrel with 1:8 in twist rifling and a birdcage style flash hider. The bolt is machined from 9310 alloy steel, and the furniture included is a CAR-15 style handguard without aluminum heatshields, an M4 buttstock, and a Ruger designed pistol grip. The included sights are a fixed front sight post and a Ruger Rapid Deploy rear flip-up sight. The gas block and sight post design is proprietary to Ruger and includes a quick detach sling swivel socket and bayonet lug.

The MPR model uses a 9 in mid-length gas system and a radial port muzzle brake, and also includes a free-float handguard with M-LOK accessory slots and a continuous top picatinny rail, and either a Magpul or B5 Systems buttstock and pistol grip.

The AR-556 Pistol has a 10.5 in barrel with a free float handguard with M-LOK slots and an SB Tactical SBA3 Pistol Stabilizing Brace, and is also available in .300 AAC Blackout and .350 Legend.

All models include a standard 30 round Magpul PMAG in the box, except those sold in states with magazine capacity limits where a 10 round aluminum magazine is included.

Marketing lawsuit
In 2021, after the Boulder shooting, families of five of the victims have sued Sturm, Ruger & Co. for "marketing its AR-556 pistol, which resembles a rifle, in a 'reckless' and 'immoral' way that promoted its killing capability and glorified lone gunmen." The Protection of Lawful Commerce in Arms Act limits the legal liability of gun manufacturers. However, they can still be sued for their marketing practices.