What triggers a double-feed malfunction in firearms?

A double-feed malfunction occurs when two cartridges attempt to enter the chamber of a firearm at the same time. This situation generally arises when a round that is already partially seated in the chamber fails to fully eject, while another round is fed from the magazine. As a result, this overlap creates a blockage, preventing the firearm from cycling properly.

It's important to understand that this type of malfunction is specifically characterized by the conflict of two rounds in the chamber area, leading to operational failure. Other factors, such as magazine issues or cleaning habits, can cause different types of malfunctions but do not typically result in a double feed. For instance, overfilling a magazine may cause feeding issues, while improper cleaning might lead to jams or malfunctions related to dirt or debris—distinct from the double feed scenario.