Which malfunction occurs if there is a projectile lodged in the barrel of the M249 AR?

A projectile lodged in the barrel of the M249 AR is characteristic of a squib load malfunction. A squib load occurs when a cartridge produces insufficient pressure to propel the projectile through the entire length of the barrel, resulting in a bullet becoming stuck within the barrel. If another round is fired after the projectile has become lodged, this can create a very dangerous situation known as a “barrel obstruction,” which can potentially lead to serious damage to the firearm or injury to the shooter.

In contrast, other types of malfunctions like failure to eject, double feed, and failure to chamber involve different mechanisms within the firearm's operation and do not specifically relate to a projectile being stuck in the barrel. A failure to eject occurs when a spent cartridge case does not exit the chamber, while a double feed refers to a situation where two rounds are attempting to be fed into the chamber simultaneously. Failure to chamber happens when a round does not seat properly in the chamber, which is also unrelated to a lodged projectile. Thus, recognizing a squib load as the correct answer is critical for safe firearm handling and maintenance.