cartridge. You can tell the difference between the M254
and live ammunition by its appearance and by the feel
of its nylon composition. M50 configuration
characteristics are shown in table 7-1.
M54A1 HIGH-PRESSURE TEST CARTRIDGE
The M54A1 cartridge is used only for proof firing
of the gun at the place of manufacture. The projectile is
made from a solid steel bar. It has a standard rotating
band. The M103 or M103B1 cartridge case is used with
the M52A3B1 electric primer.
M55A2 TARGET PRACTICE CARTRIDGE
The M55A2 cartridge has no explosive filler in the
projectile. The solid nose is made of aluminum alloy.
The projectile shape and ballistic properties are similar
to those of the other M50-configured ammunition. The
cartridge is used for practice firing, boresighting
weapons, and testing new guns. The M103 cartridge
case and M52A3B1 electric primer make up this
cartridge.
M56A3 HIGH-EXPLOSIVE INCENDIARY
CARTRIDGE
The M56A3 or M56A4 projectile is used in the
M56A3 cartridge. The projectile is loaded with an
incendiary and explosive composition, giving the
combined effect of the blast of a high-explosive charge
plus a fire-starting ability.
Both the M56A3 and M56A4 are loaded with
aluminized composition A-4. The major difference
between the projectiles is their construction. The
M56A3 has a baseplate to prevent ignition of the HEI
charge by the propellant. The M56A4 does not have the
baseplate, and it has approximately 10 more grains of
A-4. Both cartridges use the M103 case, M52A3B1
electric primer, and the M505A3 PD fuze.
M220 TARGET PRACTICE-TRACER
CARTRIDGE
The M221 projectile is used with the M220
cartridge. The M221 projectile is similar to the M55A2
7-3
Cartridge
Approximate Unit Weight (grains)
Total wt.
(grains)
(approx.)
Designation
Type
M103 case
M52A3B1
Electric
primer
Propellant
Projectile
Remarks
M51A1B1/
M51A2
M54A1
M55A2
M56A3
M220
M242
M254
Dummy
HPT
TP
HEI
TP-T
HEI-T
Dummy
1,775
1,855
1,855
1,855
1,855
1,855
n/a
None
22
22
22
22
22
None
635
(inert)
590
590
590
590
590
None
1,520
1,965
1,521
1,565
1,470
1,535
n/a
3,850
(min)
4,392
3,935
3,965
3,935
3,865
4,005
M103A1
Steel case
M505A3 fuze
required
M505A3 fuze
required
Plastic
Table 7-1.—M50 Configuration Ammunition Characteristics
