What type of magazine is specified for use in the M9 service pistol?

The M9 service pistol is designed to utilize a staggered-stacked magazine, which allows for a higher capacity while maintaining a compact size. This design features rows of cartridges stacked in an alternating pattern, enabling the magazine to hold more rounds within a smaller width. This is particularly beneficial for military and law enforcement applications, where the ability to carry extra ammunition is crucial without significantly increasing the firearm's size.

Other magazine types, such as single-stack magazines, would limit the number of rounds that could be carried, making them less practical for the M9's intended use. Drum magazines are larger and bulkier, typically used in different contexts where high-capacity ammunition is needed but are not standard for the M9. Clip-fed magazines, on the other hand, are designed to hold cartridges together for easier loading into a firearm but are not a specific feature of the M9, which relies on its proprietary staggered-stacked magazine for optimal performance and reliability.