"This 1942 manual is published for the information and guidance of personnel using the 20mm aircraft gun materiel M1 and M2 and contains technical information requried in the identification, use, and care of the materiel."
This manual is intended to prescribe the duties to be performed by the personnel manning antiaircraft machine guns, and to explain the mechanical action of the gun and the workings of related materiel so that antiaircraft machine-gun equipment.
This sub-course is designed to train the skills necessary for performing tasks related to setting up and march ordering an aiming circle; measuring angles with an aiming circle...