U.S. special operations forces this summer will begin testing a new assault rifle, which is expected to be more accurate and less cumbersome than current weapons.

Known as the special operations combat assault rifle, or SCAR, the weapon comes in 5.56 mm light and 7.62 mm heavy versions that are designated the Mk 16 SCAR-L and Mk 17 SCAR-H. Variants include standard, close quarters combat and sniper.

The SCAR-L is intended for close combat while the SCAR-H is meant for longer ranges. The initial production plan also includes an Mk 18 enhanced grenade launcher. More variants are expected to evolve from the core design.

Troops will be able to fire a variety of ammunition from the same rifle, and the entire SCAR family will have interchangeable parts, said Army Lt. Col. Deac Heilig, systems acquisition manager at the U.S. Special Operations Command.

The manufacturer of the rifle, FN Herstal, is testing different interchangeable barrels, he said in an interview.

Commonality of parts between SCAR versions is meant to reduce the training, supply and maintenance burdens. “Currently our special operations folks have a golf bag filled with guns,” said Paul Evancoe, director of military operations at FN Manufacturing. “We’ve given them a truly modular weapon … That eliminates the requirement for all the other clubs in the bag.”

The SCAR-L will replace the M4A1 close-quarters battle rifle and Mk 12 weapons now used by special operators. The SCAR-H will replace the M14 and Mk 11. All six variants of the two main versions share the same control arrangement, handling and maintenance procedures. “Once you’re trained on the gun, it’s the same for any variant,” said Evancoe.

Common parts also help cut costs, Evancoe noted. “They engineered it with a concept of keeping the cost of manufacturing down for both heavy and light by using just about the same stuff for everything.” The one-piece rail and frame of the new rifle enables the operator to change and level barrels quickly, which permits tailoring the gun to different situations.

All SCAR versions also use the same accessories, including sights and scopes. They will accommodate the accessory kit known as “special operations peculiar modification,” now under development for the current M4 rifle. SCAR can also be fitted with M4-style grips and other aftermarket items. “Special ops guys love to customize their personal weapons,” said Evancoe.

SOCOM launched the program in September 2003, and touted SCAR as the first assault-rifle competition since 1941. Fourteen operators tested competing weapons at the Naval Surface Warfare Center in Crane, Ind.

After it was selected to make the rifle, FN Herstal continued to modify the design based on input from users. Operators, for example, asked for a folding sight. FN engineers at the company’s rapid-prototyping facility in Belgium fabricated one overnight. A pushbutton lock for the sight was added in hours. “To duplicate that capability [in the United States] would require a heck of a capital investment,” said Evancoe.

A SOCOM team continues to visit the Herstal facility to review engineering changes to the weapon. “This is a very efficient way to do it because the contracting officer who has to approve the changes is sitting right there with the operators,” he added.

Relying on anthropometric analysis, SCAR designers sized the pistol grip to accommodate most hands. Ambidextrous safety mechanisms, magazine and bolt releases, and charging handles can be used by southpaws and even by operators wounded in combat. A telescoping, folding stock adjusts the length of the weapon to individual body size and firing positions, and makes the SCAR easier to hide under clothing or in small bags. The folding stock is also an advantage for operators parachuting from aircraft, fast-roping from helicopters or simply entering or leaving ground vehicles, explained Evancoe.

FN engineers gave the SCAR-L and SCAR-H a relatively low rate of fire of 600 to 650 rounds per minute on automatic. Most weapons like the M16 and M14 fire around 800 rounds per minute but make it difficult to hold the weapon on target for the full burst. “A high cyclic rate doesn’t buy you anything,” said Evancoe. “If you’re more accurate with a lower rate of fire, you’ll use less ammunition because you can put your first, second and third rounds on target.”

SOCOM wants the rifle to fire both existing and yet-to-be-developed rounds, said Heilig. “The exact caliber and ammunition will be determined based on optimum accuracy and lethality in each of the intended operational scenarios as well as availability.” A gas port selector was engineered into the SCAR to accommodate new types of ammunition.

Another SOCOM priority was reliability in harsh operating environments. Special coatings make the rifle suitable for Navy SEALs, who may have to fire weapons that were submerged for long periods.

The manufacturer claims that the weapon will fire 90,000 rounds without overhauls. The intended barrel life is 35,000 to 40,000 rounds—twice that of M16-family weapons. Barrels can be changed in the field, which cuts back on depot maintenance, said Evancoe.

SCAR prototypes will be distributed to operators for testing on an undisclosed schedule. “What they’re going to do is tweak that gun and come back with engineering change proposals,” said Evancoe. FN Herstal will produce the rifles at its South Carolina manufacturing line. The company has made M16A-2s and A-4s for U.S. military for the last five years and will use the same production machinery and workers for SCAR.

The original SCAR solicitation specified production quantities of 84,000 SCAR-L standard, 28,000 SCAR-L for close-quarters combat, 12,000 SCAR-L sniper, 15,000 SCAR-H standard, 7,000 SCAR-H close-quarter combat and, 12,000 SCAR-H sniper variants.