Usaaf air gunnery training

That's what they thought at the time PNK but tracer was a mixed blessing where gunners thought that 'hosing' until the tracer was 'on' would give hits but it's deceptive!

A very interesting secret program (!) run by the USAAF during WW2 was 'Operation Pinball' in which specially armored (!) P39 aircraft were live-fired upon by trainee bomber crews using special frangible bullet ammunition.