There were several different types of machine guns in use. Most fell into the "medium" category, and had a bore typically ranging from 6.5 to 7.92mm. The heavy machine guns tended to have a bore in the vicinity of 12.7mm, but also includes the 14.5mm KPV machine gun. 20mm and larger are considered cannons.
Used extensively.
Yes. There were machine guns in WW1. There were Gatlin Guns, a type of machine gun, in the Civil War.Yes
Kill people
rifles and machine guns
All of the major players possessed machine guns by the outbreak of the war.
unknown
it affected it by gas.
They were not yet invented- did not exist.
machine guns, submarines and poisen gas
machine guns, mustard gas, tanks
machine guns, mustard gas, tanks
All of them. Very popular weapon.