There are two basic models of the weapon. The 5.56mm SCAR-L weighs 7.7 pounds (empty), while the 7.62mm SCAR-H weighs 8.5 pounds (empty). A 30 round 5.56mm magazine weighs a little under a pound, while a 20 round magazine of 7.62mm ammo weighs a little over a pound. Special sights can weigh a pound or two, so a fully loaded SCAR won't weigh much more than ten pounds. FN also came up with a grenade launcher for SCAR.
Both models operate the same way, and have many interchangeable parts. SCAR-L is basically a replacement for the M4, which was designed (with a shorter barrel) as a close combat version of the M16. The SCAR-H will replace the M14, a 1950s era 7.62mm weapon (a replacement for the World War II M1) that is still favored for long range and sniper work.
The current SCAR design is the result of much feedback from the field. For example, the rate of fire was lowered to 600 RPM (rounds per minute) from the 800 typical with the M14 and M16. This makes SCAR easier to hold on target when firing full auto.
SCAR-H can be quickly converted to fire AK-47 ammo (the 7.62x39 round) with a changeout of the barrel and receiver. This also makes it easy for SOCOM to adopt the new 6.8mm round. Both models can be fitted with a longer and heavier sniper barrel. SCAR is built to be more rugged than the M-16. The barrel is good for some 36,000 rounds, twice as many as the M-16. Barrels may be switched by users without special tools. Both models of SCAR take all the special sights and other accessories SOCOM troops favor. SCAR is meant to be easily modified and personalized for each user. Its expected that SOCOM experience with SCAR will influence the next generation of U.S. Army and Marine Corps small arms.
SCAR (Special operations forces Combat Assault Rifle) has begun field testing with American commandoes. SOCOM (Special Operations Command) did not want to wait for the U.S. Army to finish work on their similar XM-8 rifle. SOCOM has the money, and authority to develop their own weapons. In this case, SOCOM wanted a weapon that did everything the XM-8 did, and a little more. Some 22 months ago, SOCOM asked rifle manufacturers to submit proposals, and FN (a Belgian firm) came up with the best ideas. One advantage FN has was its ability to quickly implement requests for design changes. FNs rapid prototyping shop was often able to turn out a new part in hours. This, and FNs long history of good weapons design, gave them the edge.