By World War I, all of the major powers were experimenting with aircraft mounted cannon; however their low rate of fire and great size and weight precluded any of them from being anything other than experimental.
All of the major powers were experimenting with aircraft mounted cannon. This was by World War I. All of the major powers were experimenting with however their low rate of fire. This was by World War I. All of the major powers were experimenting with great size and weight precluded any of them from being anything other than experimental. This was by World War I.