What type of magazine is used in the M16A3 service rifle?

The M16A3 service rifle utilizes a double-stacked box magazine. This design allows the magazine to hold a higher capacity of ammunition while maintaining a relatively compact and manageable size. The double-stacked configuration enables two columns of cartridges to be stored side by side, which enhances the overall capacity of the magazine and facilitates faster reloading compared to single-stacked designs.

The double-stacked magazine is essential for the M16A3 in combat situations, as it offers a balance between weight and capability, providing soldiers with a sufficient number of rounds to engage targets effectively without needing frequent reloads. This design is a standard for many modern military rifles, attributing to its reliability and efficiency during operations.

In contrast, the other options do not accurately represent the magazine type used in the M16A3. Single-stacked box magazines, while simpler and compact, are not suited for the high-capacity needs of military engagements. Drum magazines can hold more ammunition but are bulkier and can be less reliable in certain conditions. A detachable tube, while being a different design concept, does not apply to magazines used in rifles like the M16A3, which specifically require a box magazine for optimal function.