U.S. Army Staff Sgt. Ruben Romero, from Fort Benning, Ga., demonstrates a magnifying video camera and thermal imaging on the M4 rifle during a demonstration in Riga, Latvia, in this Nov. 27, 2006, file photo. Troops in Afghanistan and Iraq have complained that the standard-issue M4 rifles need too much maintenance and jam at the worst possible times.

Washington ? It was chaos during the early morning assault last year on a remote U.S. outpost in Afghanistan, and Staff Sgt. Erich Phillips’ M4 carbine had quit firing as militant forces surrounded the base. The machine gun he grabbed after tossing the rifle aside didn’t work either.

When the battle in the small village of Wanat ended, nine U.S. soldiers lay dead and 27 more were wounded. A detailed study of the attack by a military historian at Fort Leavenworth, Kan., found that weapons failed repeatedly at a “critical moment” during the firefight on July 13, 2008, putting the outnumbered American troops at risk of being overrun by nearly 200 insurgents.

Which raises the question: Eight years into the war against the Taliban in Afghanistan, do U.S. armed forces have the best guns money can buy?

Despite the military’s insistence that they do, a small but vocal number of troops in Afghanistan and Iraq has complained that the standard-issue M4 rifles need too much maintenance and jam at the worst possible times.

A week ago, eight U.S. troops were killed at a base near Kamdesh, a town near Wanat. There’s no immediate evidence of weapons failures at Kamdesh on Oct. 3, but the circumstances were eerily similar to the Wanat battle: insurgents stormed an isolated stronghold manned by American forces stretched thin by the demands of war.

Army Col. Wayne Shanks, a military spokesman in Afghanistan, said a review of the battle at Kamdesh is under way.

“It is too early to make any assumptions regarding what did or didn’t work correctly,” he said.

Complaints about the weapons the troops carry, especially the M4, aren’t new. Army officials say that when properly cleaned and maintained, the M4 is a quality weapon that can pump out more than 3,000 rounds before any failures occur.

The M4 is a shorter, lighter version of the M16, which made its debut during the Vietnam War. Roughly 500,000 M4s are in service, making it the rifle troops on the front lines trust with their lives.

Sen. Tom Coburn, R-Okla., a leading critic of the M4, said Thursday the Army needs to move quickly to acquire a combat rifle suited for the extreme conditions U.S. troops are fighting in.

U.S. special operations forces, with their own acquisition budget and the latitude to buy gear the other military branches can’t, already are replacing their M4s with a new rifle.

“The M4 has served us well but it’s not as good as it needs to be,” Coburn said.

Battlefield surveys show that nearly 90 percent of soldiers are satisfied with their M4s, according to Brig. Gen. Peter Fuller, head of the Army office that buys soldier gear. Still, the rifle is continually being improved to make it even more reliable and lethal.

Fuller said he’s received no official reports of flawed weapons performance at Wanat. “Until it showed up in the news, I was surprised to hear about all this,” he said.

The study by Douglas Cubbison of the Army Combat Studies Institute at Fort Leavenworth, Kan., hasn’t been publicly released. Copies of the study have been leaked to news organizations and are circulating on the Internet.