The BOLO Report posted a good article on repeated cycling of individual rounds of ammunition causing a failure to fire. The issue came to light after a Georgia-based officer had a failure to fire malfunction during a use of force incident. It was determined that the chambered round failed to fire due to the primer mix being knocked out of the primer during repeated cycling of the same round at night when he unloaded his weapon after work.
While it came to light during an LE incident, the situation is even more likely to occur with military ammo as troops are required to regularly unload their weapons. Oftentimes, that round goes right back into the top of the magazine it was removed from and this is accomplished over and over throughout the course of a tour.
It is important for personnel that do not regularly expend their ammo to rotate their cycled rounds.
Read it here.