A history of the Briggs Sperry Model 13 ball turret which was integrated into the design of the B-17 and B-24 aircraft during WW2, including specifications for two of the models.
Aviation and Military History
A history of the Briggs Sperry Model 13 ball turret which was integrated into the design of the B-17 and B-24 aircraft during WW2, including specifications for two of the models.