B-17 models were modified as the war progressed to take into account combat lessons learned. The B-17F models lacked sufficient forward facing firepower. The Germans exploited this vulnerability by usually attacking head on. A temporary solution was to incorporated and field modified nose flexible mounted .50 caliber machine gun. This was replaced with the Bendix chin turret at the end of 1943. Most 100th bomb group bomber should have chin turrets by episode 7. None of the bombers shown in episode 7, 8, or incorporated chin turrets.