Which of the following is essential for maintaining accuracy in machine gunnery?

Adequate training and practice are fundamental for maintaining accuracy in machine gunnery because they ensure that the operator can effectively and consistently control the weapon system. Mastery of various shooting techniques, such as proper stance, aiming, and trigger control, contributes significantly to performance under diverse conditions. Regular training allows gunners to develop muscle memory and situational awareness, which are critical for engaging targets accurately, especially in dynamic environments.

While other factors, such as regular calibration of optics, can help maintain accuracy, they are secondary to the proficiency gained through consistent practice and experience. Replacing parts frequently might address mechanical issues but does not directly influence a gunner's skill level. Similarly, using only factory ammunition ensures standardization and performance consistency, but it doesn't replace the need for the operator to develop the necessary skills through repeated practice and training. Thus, the emphasis on training and practice is paramount to achieving and maintaining high levels of accuracy in machine gunnery.