What type of magazine does the M17 handgun use?

The M17 handgun, which is the U.S. Army's Modular Handgun System, utilizes a magazine that can hold either 17 or 21 rounds. This design allows for flexibility in capacity depending on the specific type of magazine used. The standard magazine holds 17 rounds of 9mm ammunition, while an extended version is available that can hold 21 rounds. This is significant as it offers soldiers increased firepower without the need to frequently reload, improving their operational efficiency in various combat situations. The higher capacity also aligns with modern military needs for enhanced fire capability.

The other options do not accurately reflect the specifications of the M17's magazine, as none of them include the 17 or 21 round capacities that define its design.