Malfunction has the Army inspecting M4s and M16s
he Army is investigating after an unintentional firing of an M4A1 carbine while its selector switch was moved between “semi” and “auto.”

The problem has affected at least 881 carbines, and it requires adding a function check on all converted M4A1s and modifying shooter immediate action drills.

The U.S. Army Tank-automotive and Armaments Command sent out its first safety message on March 26, noting the selector switch firing.

“The M4A1 was charged and the weapon’s selector was positioned between ‘semi’ and ‘auto.’ When the weapon’s trigger was pulled, the weapon did not fire. When the selector was then moved into either ’semi’ or ’auto,’ the weapon fired without a trigger pull.”

The malfunction was found on three weapons during on-site testing at Fort Knox, Kentucky.
 
Then, a second message, sent out on April 16, noted that the malfunction issue “is now believed to go beyond just the M4A1 PIP [product improvement program] weapons.

The new order expanded weapons testing to M16 series rifles.

The second message also noted that 881 M4A1 carbines exhibited the unintended discharge problem.