All of them.
Every country
Yes, machine guns were used in WW2.
All of the major players possessed machine guns by the outbreak of the war.
machine guns and rifles
Did you want to know what calibers were used in machine guns or perhaps what cartridges are for machine guns only.
Efficiency
it used machine guns
Used extensively.
machine guns and planes the guns were ak47
it depends on country but around 7.5-8mm for infantry but some machine guns used 12.7mm .5 inch
The weapons that were used in Kokoda were rifles, revolvers and Lewis Machine guns by the Australians and Heavy machine guns, mortars and mountain guns by the Japanese
Machine guns have a higer rate of fire and so they shoot bulets faster