Washington (AP) A military historian has found that U.S.

soldiers' weapons failed repeatedly during a firefight in Afghanistan last year that left nine Americans dead.

The unreleased study is by Douglas Cubbison of the Army Combat Studies Institute at Fort Leavenworth, Kan. It's based on an Army investigation and interviews with soldiers who survived the July 2008 attack.

Soldiers said their weapons were meticulously cared for and routinely inspected by commanders, but still had breakdowns.

The failures put the outnumbered U.S. troops at risk of being overrun by nearly 200 insurgents. And that raises the question of whether the U.S. armed forces have the best guns available.

The military insists that they do. But some critics say the standard-issue M4 rifles need too much maintenance and jam at the worst possible times.

One critic is Sen. Tom Coburn. The Oklahoma Republican says the Army needs a combat rifle suited for the extreme conditions faced by U.S. troops.

U.S. SPECIAL operations forces are already replacing their M4s with a new rifle.

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