"The United States Marine Corps (USMC) Designated Marksman Rifle (DMR) uses the new enhanced M14 rifle. The M14 rifle has recently seen action with the 26th Marine Expeditionary Unit in Kandahar, Afghanistan."
M14 Rifle and M14A1 Rifles
"Already field-tested in Afghanistan, the DMR version of the 7.62mm M14 is just one of the new tools being used in America's war on terrorism by the U.S. Marine Corps' 4th Marine Expeditionary Brigade Antiterrorism unit."
United States Marines Antiterrorism Force
Considering the type of firefights these guys are getting into (small skirmishes against slippery enemies) this seems to make sense- accuracy is probably more important than rate of fire.