Last year, the U.S. Army, noting the success of U.S. Navy SEALs with rebuilt M-14 rifles (the EBR, or Enhanced Battle Rifle), converted 5,000 7.62mm M-14s to the EBR standard. This costs $3,000 per rifle, and involved using a high quality aluminum chassis, an adjustable stock, pistol grip, and standard rail for mounting scopes, plus other tweaks. The resulting EBR comes with a ten power scope, but any other can be mounted.
Designed for sharpshooters and snipers, the EBR weighs six pounds more (unloaded) than the standard M-14, and 8.5 pounds more than the M-4 assault rifle. But the EBR is much more accurate than either of those weapons, and since last year, each army infantry squad in Afghanistan has been issued two EBRs. Thus the nine man squad in Afghanistan has two 5.56mm machine-guns, five 5.56mm assault rifles (some with 40mm grenade launcher attachments) and two M-14 EBRs. The hitting power and accuracy of the 5.56mm round rapidly declines beyond 300 meters, while the EBR is still accurate and effective at 800 meters, and beyond (depending on the skill of the shooter.)
Previously, many snipers have had success using tuned up M-14s as sniper rifles. While semi-automatic and rugged, the M14 wasn't designed to be a sniper rifle. But the M-21 version of the M-14 (with a heavier barrel and other tweaks) served as the standard sniper rifle from the 1960s until 1988.
The M-14 itself was an effort to produce an improved M-1 Garand rifle. The M-1 was developed in the 1930s, and it wasn't until 1959 that the M-14 entered service. By then, the concept of the 5.56mm assault rifle was gaining momentum, and the M-14 was replaced by the M-16 by the late 1960s. But despite the success of the M-16, there was still a need for a longer range, larger caliber, rifle, especially in places like Afghanistan. The M-14, despite failing to fill the role as standard infantry role, continued, and continues, to serve as an excellent "sharpshooters" rifle.
Equipping 22 percent of American infantry in Afghanistan with the M-14 EBR simply recognizes the special characteristics of combat there. British infantry squads in Afghanistan, for example, have made similar adjustments. For example, when the troops will not be travelling long distances, over rough terrain, and expect to encounter armed resistance, they will carry more firepower, including more long range weapons. Thus an eight man squad will go out with two men armed with L85 5.56mm assault rifles (one equipped with a 40mm grenade launcher), two with 5.56mm LSW automatic rifles (an L85 with a longer and heavier barrel), two with 5.56mm FN Minimi machine-guns and two with 7.62mm L129A1 semi-automatic sharpshooter rifles. Most squads already have one man armed with a 7.62mm sharpshooter rifle.
American squads will sometimes scrounge up other weapons as well. Wise commanders will let this go on, trusting experienced troops to know what works best for them.