Which controversial product decision led to widespread M16 rifle failures during the Vietnam War, resulting in an emergency military product recall in 1967?

During the Vietnam War, a major product failure threatened American troops' lives and led to congressional investigations. The early M16 rifle, touted as revolutionary military technology, suffered catastrophic malfunctions in combat conditions. This product recall crisis represents one of military history's most significant procurement and marketing failures, where misleading claims about the rifle's self-cleaning properties and hasty deployment decisions had deadly consequences.

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Switching from the originally specified IMR powder to cheaper ball propellant without adjusting the rifle's operating system
Using aluminum instead of steel for the rifle barrel to reduce weight
Removing the forward assist mechanism to simplify production
Changing from wooden to plastic furniture to improve durability in jungle conditions