Cover, Spare Barrel M8 Canvas Cover

This is a canvas cover for a machine gun barrel from WWII. Many other examples have 1943 on them although this one is missing the date. Anyway it is clear it is from WWII. It fit a barrel 36" long. From what I have seen this is for a M2 .50 cal machine gun for the aircraft mounted machine guns although I am not 100% sure. No one seems to have actually put the barrel that matches into the case.
Let's see if we can show all the military forums that we can put this question to rest and see exactly which barrel went into it. The case is for a WWII US weapon.
Fully automatic belt fed weapons not only needed to be reloaded often unlike as seen on TV and movies but the barrel also needed to be replaced. They tend to melt if not replaced often. By often that means every few minutes. Probably not easy in combat conditions and the gun fired until it quit working.