What type of ammunition is typically used in machine guns for optimal performance?

High-velocity rounds are typically used in machine guns for optimal performance due to their ability to deliver greater kinetic energy on target, which enhances stopping power and effectiveness. These rounds are designed to maintain accuracy over longer distances and ensure that the rounds can effectively penetrate various types of materials, such as body armor, making them ideal for military and defense scenarios. Additionally, the higher velocity provides a flatter trajectory, reducing the needed elevation adjustments over distance and improving overall user accuracy during rapid fire.

In contrast, low-caliber rounds may not provide the necessary impact force required for effective engagement of hardened targets, while low-velocity projectiles might result in decreased accuracy and effectiveness over longer ranges. Mechanically loaded shells, while useful in certain contexts, do not reflect the automated firing mechanisms that are standard in modern machine guns which operate more efficiently with high-velocity ammunition. Therefore, high-velocity rounds are recognized as the optimal choice for achieving the desired performance characteristics in machine gun applications.