 This anxiety among green pilots heightened through the use of the .50 calibre guns on American aircraft.They out-ranged the MG 151/20 cannon and MG 17 machine gun on German fighters, and in a slow-closing chase the German pilot often had to sit through several minutes of American gunfire before they got within effective firing range of their own armament.American gunners saturated the air with tracers to disrupt or ward of attacks.