20 x 110mm HS United States
Details
| Type | TP |
|---|---|
| Projectile | steel, aluminum windscreen, black, 1 copper driving band Driving Band Markings: GMI-1-1-129--53-20MM M99 |
| Case | brass |
| Primer | percussion, flat, brass, 5-stake crimp |
| Headstamp | G.M.S. 1943 20MM M21A1. |
| Notes | This may be a reload since the projectile isn't crimped, although it is very secure in the case. |