The Special Operations Forces (SOF) Combat Assault Rifle, or SCAR, is a modular rifle made by FN Herstal (FNH) for the United States Special Operations Command (SOCOM) to satisfy the requirements of the SCAR competition. This family of rifles consist of two main types. The SCAR-L, for light, is chambered in the 5.56×45mm NATO cartridge and the SCAR-H, for heavy, fires 7.62×51mm NATO. Both are available in Long Barrel and Close Quarters Combat variants.

The FN SCAR systems completed low rate initial production testing in June 2007. After some delays, the first rifles began being issued to operational units in April 2009, and a battalion of the US 75th Ranger Regiment was the first large unit deployed into combat with 600 of the rifles in 2009. The US Special Operations Command has currently cancelled their purchase of the Mk 16 SCAR-L and are planning to remove the rifle from their inventory by 2013. However, they plan to purchase 5.56 mm conversion kits for the Mk 17, supplanting the loss of the Mk 16. The SCAR is now one of the competing weapons in the Individual Carbine competition which aims to find a replacement for the M4 Carbine.

The SCAR is manufactured in two main versions; Light (SCAR-L, Mk 16 Mod 0) and Heavy (SCAR-H, Mk 17 Mod 0). The L version fires 5.56×45mm NATO using improved STANAG (M16) magazines. The H fires the more powerful 7.62×51mm NATO from a newly designed 20-round magazine. Different length barrels will be available for close quarters battle and for longer-range engagements. The initial solicitation indicated that the SCAR-H would also be chambered for the 7.62×39mm M43 Kalashnikov cartridge and 6.8×43mm Remington SPC cartridge. However, FN is not currently offering other calibers.

The Mk 20 Sniper Support Rifle is based on the 7.62mm Mk 17 rifle. It includes a longer receiver, a beefed up barrel extension and barrel profile to reduce whip and improve accuracy and an enhanced modular trigger that can be configured for single-stage or two-stage operation together with a non folding precision stock.

The Mk 16 Mod 0 was intended to replace the M4A1, the Mk 18 CQBR and the Mk 12 SPR currently in SOCOM service, before SOCOM decided to cancel the order for the Mk 16 Mod 0. The Mk 17 Mod 0 will replace the M14 and Mk 11 sniper rifles. However the weapon will only supplement other weapons while issuing remains at the operators decision.

The SCAR features an integral, uninterrupted Picatinny rail on the top of the aluminum receiver, two removable side rails and a bottom one that can mount any MIL-STD-1913 compliant accessories. It has a polymer lower receiver with an M16 compatible pistol grip, flared magazine well, and raised area around magazine and bolt release buttons. The front sight flips down for unobstructed use of optics and accessories. The rifle uses a 'tappet' type of closed gas system much like the M1 Carbine while the bolt carrier otherwise resembles the Stoner 63 or Heckler & Koch G36.