
| Type | Dummy |
|---|---|
| Projectile | steel, aluminum windscreen, black, 1 copper driving band Projectile Markings: (white ink) PROJ. PRAC. 20 MM. M 99 INERT LOADED Driving Band Markings: LOT AMP-1-19-1945 20MM M99 |
| Case | brass, knurled choke crimp, 2 holes |
| Primer | percussion (fired), flat, brass, 5-stake crimp, orange annulus |
| Headstamp | AGM-1945 20MM-M21A1 |
| Notes | There is a wooden rod in the case which prevents projectile setback. |