http://atwar.blogs.nytimes.com/2010/01/12/m4-and-m4a1-guns/
"The M-4 carbine, one of the primary rifles used by the United States military, appears destined for a change. After concerns surfaced about rifles overheating in a sustained firefight in 2008 in Afghanistan, the manufacturer and the United States Army are close to agreeing on a modification to the weapon’s barrel that makes the carbine more resistant to the stresses of extended firing."
A test with a fluted barrel would be interesting...
"The M-4 carbine, one of the primary rifles used by the United States military, appears destined for a change. After concerns surfaced about rifles overheating in a sustained firefight in 2008 in Afghanistan, the manufacturer and the United States Army are close to agreeing on a modification to the weapon’s barrel that makes the carbine more resistant to the stresses of extended firing."
A test with a fluted barrel would be interesting...