How many rounds are in a burst during the sustained rate of fire for the M249?

The sustained rate of fire for the M249 is characterized by maintaining accuracy and minimizing barrel overheating during prolonged engagements. A burst of 3-5 rounds is optimal as it allows the user to deliver effective fire while managing control and ensuring the weapon does not overheat. This burst size provides a balance between volume and accuracy, which is crucial in sustained fire scenarios.

Smaller bursts help maintain accuracy, as each round fired has less impact on the shooter's ability to keep the weapon on target, particularly during longer shooting periods. The choice of 3-5 rounds reflects the operational requirements of the Marine Corps to efficiently engage targets without risking overuse of the weapon, thus ensuring reliability and effectiveness in various combat situations.