The Special Operations Forces Combat Assault Rifle - also known as SCAR - is intended redress the shortcomings of the M-4, an updated version of the M-16 which has been in service since the mid-1960s.
The U.S. military's workhorse rifle did well in Iraq, where much of the fighting was in urban settings. But its light rounds have underperformed in Afghanistan, where the Taliban tend to rely on deadly long-range fire.
An Army study found that the M-4s 5.56mm bullets don't retain enough velocity beyond 1,000 feet (300 meters) to kill an adversary. NATO commanders say U.S. firepower cannot always respond adequately to Taliban sharpshooters firing from 2,000 to 2,500 feet (600-800 meters).
The SCAR, manufactured by Belgian gunmaker FN Herstal, fulfills a specific special operations forces requirement for an easily modifiable rifle that to be used for both urban combat and for extended-distance shooting.
This called for a unique modular system accommodating not just the two main Western rifle calibers - the L-model for the light 5.56mm rounds and H-model for the heavier-hitting 7.62mm rounds - but also barrels of lengths in both calibers.
Many of the components can be interchanged between the two models. Both versions also allow soldiers to quickly replace their barrels to deal with a changing tactical situation.
Martin Fackler, a U.S. ballistics expert, said the SCAR-H round enjoys a clear advantage at long distances because the lighter 5.56mm bullets slow down significantly after about 400 meters (yards), sharply reducing their ability to inflict serious damage to the target.
"(In contrast) at 1,000 yards the 7.62 bullet is still traveling at over the speed of sound," Fackler said.
The U.S. Special Operations Command based in Tampa, Florida, first tested the SCAR in Afghanistan in 2009.
Last April, FN was awarded an initial contract for both versions of the SCAR and a separate grenade launcher. On Wednesday, FN announced that its U.S. plant in Colombia, South Carolina, has been authorized to start full-rate production.
Command spokesman Maj. Wesley Ticer said the command was still in the process of determining the exact quantities needed.
To date, Ticer said, the Special Operations Command has bought an initial batch of 850 lighter and 750 heavier rifles. Approximately $19 million has been spent so far on research, development, and procurement of the SCAR variants.
Analysts predict that more than 10,000 new rifles may be acquired over the next several years.
FN, which has been supplying weapons to the U.S. military for the past century, also hopes to enter the SCAR in a future U.S. Army contest to replace the M-4, a program potentially many times bigger than the existing one.
"We feel the SCAR is a solution that could meet that requirement," said Gab Bailey, FN's marketing director in the United States. He added that FN also has plans to export the rifle to other allied armies.
"While SCAR is initially meant for the U.S. special forces, we've built it to sell to the rest of the world," he said.
The production announcement comes as coalition commanders in Afghanistan have been placing much greater emphasis on small, maneuverable special operations units to hunt down al-Qaida militants and Taliban guerrillas rather than large, heavily armed formations.
The SCAR suits this strategy, analysts say.
"It's obviously good to have a multi-configuration weapon that you can tailor to any specific mission," said Jean-Claude Amiot, a retired French special forces colonel and firearms expert.
FN - the Fabrique Nationale des Armes D'Guerre - generally maintains a low public profile in Belgium, a country with strong pacifist policies which opposed the U.S. invasion of Iraq and keeps defense spending well below NATO's minimum.
The firm has an interesting historical association with the United States. John Browning, one of America's foremost firearms designers, worked closely with FN to create a range of weapons. Some of them, like the ubiquitous .50 caliber heavy machine gun developed in the 1920s, remain in wide use.
FN's most infamous product was the M1910 Browning pistol used by Serbian nationalist Gavrilo Princip in 1914 to assassinate Archduke Franz Ferdinand of Austria - an act that triggered World War I.