This catastrophic failure was said to be the result of an Eldest Son round. Project Eldest Son was originally performed during the Vietnam War in order to generate distrust in amongst the North Vietnamese forces against their Chinese suppliers. 7.62x39mm ammunition was specially designed to hold a small explosive charge, which would detonate when the user attempted to fire the cartridge, injuring or killing the user. This ammo was distributed by SOG troops into NVA ammo caches, with single rounds of explosive ammo placed into large quantities of “good” ammo to keep the enemy unaware of the true cause of explosion.
While there is no official record of similar unconventional warfare tactics being used in Iraq and Afghanistan, it’s entirely possible that modern SF may still be employing this tactic, or that the ammo shown in this .gif is a leftover round from that era.