US Cartridge, 20mm Ball
The Cartridge, Ball, was designed to simulate the HEI Mk. 1 for practice firing purposes. Since the projectile is cheap and easy to manufacture, its use for practice firing is economical.
The entire projectile except for the rotating band is painted black. The cut-off nose and the lack of any identifying marking on the projectile body serves to differentiate between the ball and the AP round.
Collaborative Ordnance Data Repository