OP 1664 - U.S. Explosive Ordnance (Vol. 1); Part 1 - Projectiles, Propellants, and Projectiles; Chapter 1 - Projectiles; Section 1

U.S. EXPLOSIVE ORDNANCE

PART 1 - PROJECTILES, PROPELLANT,
AND PROECTILE FUZES

Chapter 1 - Projectiles

Section 1 - Introduction

Minot Caliber projectiles

20-mm ammunition: Two types of 20-mm weapons are at present in service use in the Navy: Oerlikon antiaircraft gun and the Hispano-Suiza aircraft gun. These types dif-fer widely in construction and functioning; and it is emphasized that the ammunition, though somewhat similar in external appearance, is not interchangeable.

Ammunition for Oerlikon gun: The Oerlikon gun and its ammunition are of naval manu-facture and design. The ammunition may be distinguished from that designed for the His-pano-Suiza gun by the reduced diameter of the extractor lip at the base of the cartridge case. For identification of individual types of rounds, the body of the projectile is painted a distanctive color, as follow:

Type	Filling	Color
H.E. Mk 3	Tetryl	White
H.E. Mk 3	Pentolite	Yellow
H.E.-I. Mk 3	Tetryl and incendiary mix.	Red
H.E.-I. Mk 3	Pentolite and incendiary mix.	Light pink
H.E.-T. Mks 4 and 7*	Tetryl and tracer	Light gray
H.E.-T. Mks 4 and 7*	Pentolite and tracer	Blue
A.P.-T. Mk 9	Tracer	Black
B.L. and P. Mk 3	Inert loaded	Dark green
B.L. and T. Mk 7	Inert load and tracer	Dark green with yellow stripe
Drill	Empty	Seal brown
H.E.-I.-T.		Bright green

The Mark and Mod, manufacturer's initials or symbol, and lot number are stamped a-round the body of the projectile.

Abbreviations in Minor Calibers

H.E.	– High Explosive
I.	– Incendiary
T.	– Tracer
B.L.	– Blind Loaded
P.	– Plugged
S.D.	– Self Destructive
D.I.	– Dark Ignition

Ammunition for Hispano-Suiza Gun: This gun and its ammunition are Army-designed but have been daopted as Naval equipment with the installation of the gun on Naval pla-nes. The ammunition is distinguished from that designed for the Oerlikon gun by the ex-tractor lip on the base of the cartridge, which is the same diameter as the rest of the case. Two series of ammunition for this gun are in use. The "Old Series" consists of un-matched rounds, some adapted from British prototypes, others designed by the Army. The "New Series" is a set of ballistically matched rounds designed by the Army to super-sede those of the "Old Series". For identifiaction of specific color, as follwos:

Type	Series	Filling	Color
H.E.-I. Mk 1	Old	Tetryl and Incendiary	Body – red Bourrelet – yellow Fuze – brass Marking in black
A.P.-T. M75	Old	Tracer and inert load	Black over all Marking in white
Ball, Mk 1	Old	Inert loaded	Black over all
Dummy Drill	Old	Empty	Zinc coated
H.E.-I. M97	New	Tetryl and incendiary mix	Body – red Bourrelet – yellow Fuze – brass Marking in black
Incendiary, M96	New	Incendiary mix	Body – blue gray Nose – light blue Marking in black
A.P.-T. M95	New	Tracer	Black over all Marking in white
Practice, M99	New	Empty	Black over all Marking in white

1.1"/75 ammunition: The body of these projectiles, now obsolete items, were un-painted except for two dots below the fuze, indicating as follows:

Explosive D – Yellow dot

Tracer – Red dot

A newer color marking was proposed for the 1.1-inch ammunition. Some projectiles may be found painted as shown in column 2:

Type	Color
H.E.-T.	Light gray with white band
H.E.-T./S.D.	Dark green with white band
B.L. and P.	Red over all
B.L. and T.	Red over all with white band

40-mm ammunition: These projectiles are identified by distinctively colored bodies, as follows:

Type	Body	Band	Tip	Remarks
A.P.	Black	Black	Black	Plug in tracer
A.P.-T.	Black	White	Black
H.E.-P.	Green	Green	Green	Plug in base
H.E.-T-/S.D.	Green	White	Green
H.E./S.D.	Green	Black	Green	Dark tracer
H.E.-I.-T./S.D.	Green	White	Red
H.E.-I.-P.	Green	Red	Red	Plug in base
H.E.-I./S.D.	Green	Black	Red	Dark tracer
H.E.-I.-T.	Green with Black Band	White	Red	S.D. relay not loaded
B.L. and T.	Red	White	Red	Dummy fuze
B.L. and P.	Red	Red	Red	Dummy Fuze and plug in place
H.E.-I.-T. (D.I.)-S.D.	Green	White	Red	Dark ignition tracer

The tracer composition is either a red burning mixture in the tracer – "T" rounds – or a non-luminous burning compound in the "Self Destructive" rounds.

"Dark" and "Dark Ignition Tracer": To eliminate the blinding effect on 40-mm and 20-mm gunners from tracer fire at night and also to make the origing of tracer fire less dist-inct, these tracers were developed toward the close of the war. The dark iginition tracer is invisible until the projectile is 100 to 400 yards from the gun's muzzle, and then it is vi-sible for the rest of its time of flight. Details of these tracers are described with their ap-proproate projectile and tracer housing.