20-mm A/C Practice M99 (New Series)20-mm A/C Ball Mk 1 (Old Series)
U.S. EXPLOSIVE ORDNANCE
PART 1 - PROJECTILES, PROPELLANT,
AND PROECTILE FUZES
Chapter 1 - Projectiles
Section 11 - 20-mm PROJECTILES
20-mm A/C H.E.-I. Mk 1 (Old Series)

Over-all length, inches

3.22

Diameter of base, inches

0.770

Distance base to band, inches

0.50

Width of band, inch

0.203

Diameter at bourrelet, inch

0.784

Filling

Tetryl and Incendiary Mix

Weight of filling, pound

0.025

Weight of loaded projectile, pound

0.290

Cartridge Case

M21A1

Primer

M36

Fuzes

No. 253 Mk 1

This round is to be superseded by the H.E.-I. M97 round of the new ballistically mat-ched series. The H.E.-I. Mk 1 round is to be classified unserviceably by Naval activities as soon as replacement allowances or stocks of the M97 round are received.

Figure 75 (Part 2). 20-mm Projectiles.

20-mm A/C Practice M99 (New Series)20-mm A/C Ball Mk 1 (Old Series)