Which part of a machine gun is critical for the cooling process during sustained firing?

The cooling jacket is critical for the cooling process during sustained firing because it is specifically designed to manage the temperature of the weapon. Machine guns generate significant heat when fired continuously, which can lead to overheating, malfunctions, and even damage to the weapon. The cooling jacket surrounds the barrel and circulates coolant, often air or water, to dissipate heat away from the barrel. This design helps maintain optimal operating temperatures, ensuring the machine gun remains functional and effective during extended use.

In contrast, the muzzle brake primarily serves to reduce recoil and muzzle rise, aiding in control during firing but does not contribute to cooling. The trigger assembly functions as the mechanism for firing the weapon, and while it is essential for operation, it is not involved in managing heat. The feed tray is responsible for holding and feeding ammunition into the chamber and does not play a role in the cooling process either. Thus, the cooling jacket is fundamental in preventing overheating and ensuring reliable performance during sustained firing.