Figure M machine gun components

a. Sights. The M249 machine gun has a hooded and semifixed front sight (Figure 1-3). The rear sight assembly mounts on the top of the cover and feed mechanism assembly. The elevation knob drum has range settings from 300 meters to 1,000 meters. Range changes are made on the M249 machine gun sight by rotating the elevation knob to the desired range setting. Rotation of the rear sight aperture (peep sight) is used for fine changes in elevation or range adjustments, such as during zeroing. Each click of the peep sight. One click moves the sight 180 degrees, or one-half turn. This equals a one-half-mil change in elevation, which is .5 cm at 10 meters. The sight adjusts for windage by rotating the windage knob. Each click of windage adjustment also equals a one-half-mil change, which is .5 cm at 10 meters. There is also a windage sliding scale marked with index lines for centering the rear sight aperture.

Figure 1-3. Sights.

b. Safety. The safety (Figure 1-4) is in the trigger housing. The safety is pushed from left to right (red ring not visible) to render the weapon safe, and the bolt cannot be released to go forward. The safety is pushed from right to left (red ring visible) to render the weapon ready to fire. The cocking handle on the right side of the weapon is used to pull the bolt to the rear.

RED RING VISIBLE RED RING NOT VISIBLE

READY TO FIRE ON SAFE

RED RING VISIBLE RED RING NOT VISIBLE

READY TO FIRE ON SAFE

Figure 1-4. M249 machine gun safety.

1-3. AMMUNITION

The M249 machine gun uses several different types of 5.56-mm standard military ammunition. Soldiers should use only authorized ammunition that is manufactured to US and NATO specifications. The 5.56-mm NATO cartridge is identified by its appearance, the painted projectile tips, the stamped manufacturer's initials and year of manufacture on the base of the cartridge case, and the markings on the packing containers. When removed from the original packing container, the cartridge can be identified by its physical characteristics. The M193 and M196 cartridge for the M16 can be fired with the M249, but accuracy is degraded; therefore, it should only be used in emergency situations when M855 or M856 ammunition is not available.

a. Type and Characteristics. The specific types of ammunition (Figure 1-5) and its characteristics are as follows.

A059 Ammunition
Figure 1-5. Cartridges for the M249.

(1) Cartridge, 5.56-mm ballM855 (A059). The M855 cartridge has a gilding, metal-jacketed, lead alloy core bullet with a steel penetrator. The primer and case are waterproof. This ammunition is linked by a disintegrating metallic split-linked belt so that the ammunition can feed from the ammunition box (Figure 1-6). In an emergency, the M855 round can also be fired from the M16A2, A3, or A4 when loaded in a 20- or 30-round magazine. It is identified by a green tip, has a projectile weight of 62 grains, and is 2.3 cm long. This is the NATO standard round. It is effective against personnel and light materials, not vehicles.

Figure 1-6. M855 cartridges in metallic belt.

(2) Cartridge, 5.56-mm tracer, M856 (A064). This cartridge has a projectile weight of 63.7 grains and lacks a steel penetrator. It is identified by an orange tip. The tracer is used for adjustments after observation, incendiary effects, and signaling. When tracer rounds are fired, they are mixed with ball ammunition in a ratio of four ball rounds to one tracer round. The DODAC for ball and tracer mix is A064.

(3) Cartridge, 5.56-mm dummy M199 (A060). This cartridge can be identified by the six grooves along the side of the case beginning about one-half inch from its head. It contains no propellant or primer. The primer well is open to prevent damage to the firing pin. The dummy round is used during mechanical training, dry-fire exercises, and function checks.

NOTE: The 5.56-mm NATO cartridge may be identified by its appearance, the painting of projectile tips, the stamping of the manufacturer's initials and year of manufacture on the base of the cartridge case, and the markings on the packing containers. When removed from the original packing container, the cartridge can be identified by its physical characteristics. The M193 and M196 cartridge for the M16 can be fired with the M249, but accuracy is degraded; therefore, it should only be used in emergency situations when M855 or M856 ammunition is not available.

(4) Cartridge, 5.56-mm blank M200 (M2 link, A075). The blank cartridge has no projectile. The case mouth is closed with a seven-petal rosette crimp and has a violet tip. The original M200 blank cartridge had a white tip. Field use of this cartridge resulted in residue buildup, which caused malfunctions. Only the violet-tipped M200 cartridge should be used. The blank round is used during training when simulated live fire is desired. The M249 blank-firing attachment (NSN 1005-21-912-8997) must be used to fire this ammunition. (See paragraph 1-4.)

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