American Projectiles and Explosives
20mm Projectiles
20mm A.A. H.E., H.E.I., and B.L. & P. Mk 3 Mods 1-64
Overall length w/ nose fuze: 3.275 inches
Overall length w/o nose fuze: 2.625 inches
Diameter of base: 0.74 inches
Distance base to band: 0.374 inches
Width of band: 0.16 inches
Diameter at bourrelet: 0.78 inches
Filling:
-H.E.: 0.0243 pounds Tetryl or Pentolite
-H.E.I.: 0.0072 pounds incendiary mix; 0.0171 pounds Tetryl of Pentolite
Weight of loaded projectile: 0.2714 pounds
Charge/Weight ratio: 8.9%
Cartridge case:
-H.E.: Mk 2
-H.E.I.: Mk 2, 3, or 4
Primer:
-H.E.: Mk 30
-H.E.I.: Mk 30 or 31
Tracer: N/A
Fuzes:
-Nose: Mk 26 Mods 0 and 1
The explosive filling of the H.E. projectile is press-loaded in three equal increments. The H.E.I. projectile is similarly loaded, but the first increment consists of an incendiary mixture, the other two of H.E., either Tetryl or Pentolite.
This round is also issued B.L. & P., with an inert filler and a dummy nose cap.
Identification and Markings
Type ---- Color
H.E. (Tetryl) ---- White
H.E. (Pentolite) ---- Yellow
H.E.I (Tetryl) ---- Red
H.E.I. (Pentolite) ---- Light Pink
B.L. & P. ---- Dark Gray Green
The many modification numbers are to distinguish between products from different contracts.
20mm A.A. H.E.T., and B.L. & P. Mk 4 Mods 1-28 and Mk 7
Overall length : 3.025 inches
Overall length w/o nose fuze: 2.525 inches
Diameter of base: 0.74 inches
Distance base to band: 0.397 inches
Width of band: 0.16 inches
Diameter at bourrelet: 0.78 inches
Filling:
-H.E.: 0.01 pounds
-Tracer: 0.0173 pounds
Weight of loaded projectile: 0.2621 pounds
Charge/Weight ratio: N/A
Cartridge case: Mk 2
Primer: Mk 30
Tracer: Integral
Fuzes:
-Nose: Mk 26 Mods 0 and 2 (Mk 4)
-Nose: Mk 26 Mods 0 and 1 (Mk 7)
Length of tracer cavity: 1.107 inches
Diameter of tracer cavity: 0.51 inches
To eliminate the blinding flash characteristic of standard 20mm tracers fired at night, a special Dark Ignition tracer has been developed which does not light up until about 100 yards from the gun muzzle. Rounds are designated "H.E.T.D.I." Overall burning time of this tracer is four seconds; during the "dark" period there is a faint streaking in the projectile's path.
The Mk 4 and Mk 7 rounds are identical except for the dimensions of the tracer cavity, which is slightly greater in diameter and length in the Mk 4 than in the Mk 7. This somewhat reduces the tracer filling of the Mk 7.
The Mk 7 round is also issued B.L. & T. with an inert filler in the H.E. cavity and a dummy nose plug. The tracer cavity contains the standard tracer mixture.
The burster charge of the 20mm is more sensitive than the usual projectile burster charge. Accordingly, greater caution should be observed in handling.
The tracer element in these projectiles is loaded in two increments. First increment is the tracer composition, which is pressed in the after compartment by hydraulic pressure; the second increment is the "starter" mixture, which is pressed in on top of the tracer composition and is more sensitive than the latter. When the projectile is fired, the heat from the propellent charge ignites the starter which, in turn, sets off the tracer composition.
Identification and Markings
Type ---- Color
H.E. (Tetryl) ---- Light Gray
H.E. (Pentolite) ---- Blue
B.L. & T. ---- Dark Gray Green, with 1/8 inch Yellow band
20mm A.P.T. Mk 9
Overall length w/ cap and windshield : 3.051 inches
Overall length w/o cap and windshield: 2.449 inches
Diameter of base: 0.742 inches
Distance base to band: 0.315 inches
Width of band: 0.154 inches
Diameter at bourrelet: 0.784 inches
Weight of loaded projectile: 0.2686 pounds
Charge/Weight ratio: N/A
Cartridge case: Mks 3 and 4
Primer: Mk 31
Tracer: Integral
20mm A/C A.P.T. M95 (New Series)
Overall length w/ cap and windshield : 3.27 inches
Overall length w/o cap and windshield: 2.4 inches
Diameter of base: 0.76 inches
Distance base to band: 0.39 inches
Width of band: 0.203 inches
Diameter at bourrelet: 0.78 inches
Weight of loaded projectile: 0.29 pounds
Charge/Weight ratio: N/A
Cartridge case: M21A1
Primer: M36A1
Tracer: Integral
The tracer is red in color and burns for a period of about 2.25 seconds, equivalent to a range of about 1,400 yards. This round is superseding the A.P.T. M75 round of the Old Series.
20mm A/C Incendiary M96 (New Series)
Overall length w/ nose cap: 3.245 inches
Overall length w/o nose cap: 2.3 inches
Diameter of base: 0.76 inches
Distance base to band: 0.39 inches
Width of band: 0.203 inches
Diameter at bourrelet: 0.78 inches
Filling: Incendiary Mixture
Weight of filling: 0.02 pounds
Weight of loaded projectile: 0.27 pounds
Charge/Weight ratio: N/A
Cartridge case: M21A1
Primer: M36A1
Tracer: N/A
The incendiary mixture fills both the nose cap and the projectile body. No fuze is required, since the functioning is initiated by impact of the nose with the target.
20mm A/C H.E.I. M97 (New Series)
Overall length w/ nose fuze: 3.28 inches
Overall length w/o nose fuze: 2.44 inches
Diameter of base: 0.76 inches
Distance base to band: 0.39 inches
Width of band: 0.203 inches
Diameter at bourrelet: 0.78 inches
Filling: Tetryl and Incendiary Mixture
Weight of filling: 0.017 pounds
Weight of loaded projectile: 0.29 pounds
Charge/Weight ratio: N/A
Cartridge case: M21A1
Primer: M36A1
Tracer: N/A
Fuzes: Nose - M75
This round is superseding the H.E.I. Mk 1 round of the Old Series
20mm A/C Practice M99 (New Series)
Overall length w/ nose fuze: 3.27 inches
Overall length w/o nose fuze: 2.3 inches
Diameter of base: 0.76 inches
Distance base to band: 0.39 inches
Width of band: 0.203 inches
Diameter at bourrelet: 0.78 inches
Filling: None
Weight of filling: N/A
Weight of loaded projectile: 0.29 pounds
Charge/Weight ratio: N/A
Cartridge case: M21A1
Primer: M36A1
Tracer: N/A
This round is superseding the Ball Mk 1 round of the Old Series
20mm A/C H.E.I. Mk 1 (Old Series)
Overall length: 3.22 inches
Diameter of base: 0.77 inches
Distance base to band: 0.5 inches
Width of band: 0.203 inches
Diameter at bourrelet: 0.784 inches
Filling: Tetryl and Incendiary Mix
Weight of filling: 0.025 pounds
Weight of loaded projectile: 0.29 pounds
Charge/Weight ratio: N/A
Cartridge case: M21A1
Primer: M36
Tracer: N/A
Fuzes: No.253 Mk 1
This round is to be superseded by the H.E.I. M97 round of the new ballistically matched series. The H.E.I. Mk 1 round is to be classified unserviceable by Naval activities as soon as replacement allowances or stocks of the M97 round are received.
20mm A/C Ball Mk 1 (Old Series)
Overall length: 3.31 inches
Diameter of base: 0.77 inches
Distance base to band: 0.5 inches
Width of band: 0.203 inches
Diameter at bourrelet: 0.784 inches
Filling: None
Weight of filling: N/A
Weight of loaded projectile: 0.28 pounds
Charge/Weight ratio: N/A
Cartridge case: M21A1
Primer: M36
Tracer: N/A
This round is to be superseded by the practice round M99 of the new ballistically matched series. The Ball Mk 1 round is to be classified unserviceable by Naval activities as soon as replacement allowances or stocks of the M99 round are received.
20mm A/C A.P.T. M75 (Old Series)
Overall length: 3.25 inches
Diameter of base: 0.77 inches
Distance base to band: 0.5 inches
Width of band: 0.203 inches
Diameter at bourrelet: 0.784 inches
Filling: None
Weight of filling: N/A
Weight of loaded projectile: 0.37 pounds
Charge/Weight ratio: N/A
Cartridge case: M21A1
Primer: M36
Tracer: Integral
This round is to be superseded by the A.P.T. round M95 of the new ballistically matched series. The A.P.T. M75 round is to be classified unserviceable by Naval activities as soon as replacement allowances or stocks of the M95 round are received.
20mm A.A. H.E., H.E.I., and B.L. & P. Mk 3 Mods 1-64
Overall length w/o nose fuze: 2.625 inches
Diameter of base: 0.74 inches
Distance base to band: 0.374 inches
Width of band: 0.16 inches
Diameter at bourrelet: 0.78 inches
Filling:
-H.E.: 0.0243 pounds Tetryl or Pentolite
-H.E.I.: 0.0072 pounds incendiary mix; 0.0171 pounds Tetryl of Pentolite
Weight of loaded projectile: 0.2714 pounds
Charge/Weight ratio: 8.9%
Cartridge case:
-H.E.: Mk 2
-H.E.I.: Mk 2, 3, or 4
Primer:
-H.E.: Mk 30
-H.E.I.: Mk 30 or 31
Tracer: N/A
Fuzes:
-Nose: Mk 26 Mods 0 and 1
The explosive filling of the H.E. projectile is press-loaded in three equal increments. The H.E.I. projectile is similarly loaded, but the first increment consists of an incendiary mixture, the other two of H.E., either Tetryl or Pentolite.
This round is also issued B.L. & P., with an inert filler and a dummy nose cap.
Identification and Markings
Type ---- Color
H.E. (Tetryl) ---- White
H.E. (Pentolite) ---- Yellow
H.E.I (Tetryl) ---- Red
H.E.I. (Pentolite) ---- Light Pink
B.L. & P. ---- Dark Gray Green
The many modification numbers are to distinguish between products from different contracts.
20mm A.A. H.E.T., and B.L. & P. Mk 4 Mods 1-28 and Mk 7
Overall length w/o nose fuze: 2.525 inches
Diameter of base: 0.74 inches
Distance base to band: 0.397 inches
Width of band: 0.16 inches
Diameter at bourrelet: 0.78 inches
Filling:
-H.E.: 0.01 pounds
-Tracer: 0.0173 pounds
Weight of loaded projectile: 0.2621 pounds
Charge/Weight ratio: N/A
Cartridge case: Mk 2
Primer: Mk 30
Tracer: Integral
Fuzes:
-Nose: Mk 26 Mods 0 and 2 (Mk 4)
-Nose: Mk 26 Mods 0 and 1 (Mk 7)
Length of tracer cavity: 1.107 inches
Diameter of tracer cavity: 0.51 inches
To eliminate the blinding flash characteristic of standard 20mm tracers fired at night, a special Dark Ignition tracer has been developed which does not light up until about 100 yards from the gun muzzle. Rounds are designated "H.E.T.D.I." Overall burning time of this tracer is four seconds; during the "dark" period there is a faint streaking in the projectile's path.
The Mk 4 and Mk 7 rounds are identical except for the dimensions of the tracer cavity, which is slightly greater in diameter and length in the Mk 4 than in the Mk 7. This somewhat reduces the tracer filling of the Mk 7.
The Mk 7 round is also issued B.L. & T. with an inert filler in the H.E. cavity and a dummy nose plug. The tracer cavity contains the standard tracer mixture.
The burster charge of the 20mm is more sensitive than the usual projectile burster charge. Accordingly, greater caution should be observed in handling.
The tracer element in these projectiles is loaded in two increments. First increment is the tracer composition, which is pressed in the after compartment by hydraulic pressure; the second increment is the "starter" mixture, which is pressed in on top of the tracer composition and is more sensitive than the latter. When the projectile is fired, the heat from the propellent charge ignites the starter which, in turn, sets off the tracer composition.
Identification and Markings
Type ---- Color
H.E. (Tetryl) ---- Light Gray
H.E. (Pentolite) ---- Blue
B.L. & T. ---- Dark Gray Green, with 1/8 inch Yellow band
20mm A.P.T. Mk 9
Overall length w/o cap and windshield: 2.449 inches
Diameter of base: 0.742 inches
Distance base to band: 0.315 inches
Width of band: 0.154 inches
Diameter at bourrelet: 0.784 inches
Weight of loaded projectile: 0.2686 pounds
Charge/Weight ratio: N/A
Cartridge case: Mks 3 and 4
Primer: Mk 31
Tracer: Integral
20mm A/C A.P.T. M95 (New Series)
Overall length w/o cap and windshield: 2.4 inches
Diameter of base: 0.76 inches
Distance base to band: 0.39 inches
Width of band: 0.203 inches
Diameter at bourrelet: 0.78 inches
Weight of loaded projectile: 0.29 pounds
Charge/Weight ratio: N/A
Cartridge case: M21A1
Primer: M36A1
Tracer: Integral
The tracer is red in color and burns for a period of about 2.25 seconds, equivalent to a range of about 1,400 yards. This round is superseding the A.P.T. M75 round of the Old Series.
20mm A/C Incendiary M96 (New Series)
Overall length w/o nose cap: 2.3 inches
Diameter of base: 0.76 inches
Distance base to band: 0.39 inches
Width of band: 0.203 inches
Diameter at bourrelet: 0.78 inches
Filling: Incendiary Mixture
Weight of filling: 0.02 pounds
Weight of loaded projectile: 0.27 pounds
Charge/Weight ratio: N/A
Cartridge case: M21A1
Primer: M36A1
Tracer: N/A
The incendiary mixture fills both the nose cap and the projectile body. No fuze is required, since the functioning is initiated by impact of the nose with the target.
20mm A/C H.E.I. M97 (New Series)
Overall length w/o nose fuze: 2.44 inches
Diameter of base: 0.76 inches
Distance base to band: 0.39 inches
Width of band: 0.203 inches
Diameter at bourrelet: 0.78 inches
Filling: Tetryl and Incendiary Mixture
Weight of filling: 0.017 pounds
Weight of loaded projectile: 0.29 pounds
Charge/Weight ratio: N/A
Cartridge case: M21A1
Primer: M36A1
Tracer: N/A
Fuzes: Nose - M75
This round is superseding the H.E.I. Mk 1 round of the Old Series
20mm A/C Practice M99 (New Series)
Overall length w/o nose fuze: 2.3 inches
Diameter of base: 0.76 inches
Distance base to band: 0.39 inches
Width of band: 0.203 inches
Diameter at bourrelet: 0.78 inches
Filling: None
Weight of filling: N/A
Weight of loaded projectile: 0.29 pounds
Charge/Weight ratio: N/A
Cartridge case: M21A1
Primer: M36A1
Tracer: N/A
This round is superseding the Ball Mk 1 round of the Old Series
20mm A/C H.E.I. Mk 1 (Old Series)
Diameter of base: 0.77 inches
Distance base to band: 0.5 inches
Width of band: 0.203 inches
Diameter at bourrelet: 0.784 inches
Filling: Tetryl and Incendiary Mix
Weight of filling: 0.025 pounds
Weight of loaded projectile: 0.29 pounds
Charge/Weight ratio: N/A
Cartridge case: M21A1
Primer: M36
Tracer: N/A
Fuzes: No.253 Mk 1
This round is to be superseded by the H.E.I. M97 round of the new ballistically matched series. The H.E.I. Mk 1 round is to be classified unserviceable by Naval activities as soon as replacement allowances or stocks of the M97 round are received.
20mm A/C Ball Mk 1 (Old Series)
Diameter of base: 0.77 inches
Distance base to band: 0.5 inches
Width of band: 0.203 inches
Diameter at bourrelet: 0.784 inches
Filling: None
Weight of filling: N/A
Weight of loaded projectile: 0.28 pounds
Charge/Weight ratio: N/A
Cartridge case: M21A1
Primer: M36
Tracer: N/A
This round is to be superseded by the practice round M99 of the new ballistically matched series. The Ball Mk 1 round is to be classified unserviceable by Naval activities as soon as replacement allowances or stocks of the M99 round are received.
20mm A/C A.P.T. M75 (Old Series)
Diameter of base: 0.77 inches
Distance base to band: 0.5 inches
Width of band: 0.203 inches
Diameter at bourrelet: 0.784 inches
Filling: None
Weight of filling: N/A
Weight of loaded projectile: 0.37 pounds
Charge/Weight ratio: N/A
Cartridge case: M21A1
Primer: M36
Tracer: Integral
This round is to be superseded by the A.P.T. round M95 of the new ballistically matched series. The A.P.T. M75 round is to be classified unserviceable by Naval activities as soon as replacement allowances or stocks of the M95 round are received.
Next Time: 40mm Projectiles
