M254 DUMMY CARTRIDGE

The M254 cartridge is made of plastic. It is an alternate to the M51A1B1/M51A2 steel dummy 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.

Table 7-1.-M50 Configuration Ammunition Characteristics

M54A1 HIGH-PRESSURE TEST CARTRIDGE

The M544A1 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 projectile, except it incorporates a tracer in the base of the projectile.

M242 HIGH-EXPLOSIVE INCENDIARY-TRACER CARTRIDGE

The M242 projectile is used with the M242 cartridge. The projectile has a tracer in the base and aluminized composition A-4 in the forward section. It has a combined effect of a high-explosive charge plus a fire-starting ability. The projectile is assembled with the M505A3 PD fuze, the M103 case, and the M52A3B1 electric primer.

Figure 7-4.-Example of color coding and marking for M50 configuration ammunition.

IDENTIFICATION Lettering

Ammunition is identified by the color the projectile The lettering (fig. 7-4) is stenciled in waterproof is painted and by the lettering on the body of the marking ink around the body of the projectile. The first projectile. line of lettering identifies the caliber and type of

Table 7-2.-Co1or Coding and Marking for M50 Configuration Ammunition

cartridge; for example, 20MM HEI, 20MM TP, or 20MM HEI-T. The second line gives the cartridge designation; for example, M254, M55A2, or M220. The last line consists of a code number that identifies the manufacturer, interfix number, lot serial number, and year of manufacture. The color of the letters has no meaning.

Color Coding

The color codes for the M50-configured 20-mm ammunition are listed in table 7-2. You can see exactly where colors are located on the projectile. The projectile (fig. 7-4) is divided into sections marked A, B, C, and D. The sections on the projectile match the color code to columns in the figure.

By looking at table 7-2, you can identify high-explosive incendiary-tracer round M242. First, find the projectile and its color code in column A. Then, look at section A of the projectile. This section of the projectile isn't painted; therefore, section A of the projectile remains the natural color of the metal (copper). Look at column B and find the color for section B. Refer to section B of the projectile. This area is painted yellow (high explosives), and section B1 is painted red (incendiary). Use the same procedures for sections C and D. Also note the red T markings in the section B area just outside of the B1 section. The red T, and in some cases orange T, shows the presence of an incendiary explosive (tracer).