CHAPTER 1
DESCRIPTION AND COMPONENTS
This chapter describes the weapon and the types of ammunition in detail
and provides a table of general data.
1-1. DESCRIPTION
The M249 AR is a gas-operated, air-cooled, belt-and magazine-fed,
automatic weapon that fires from the open-bolt position ( Figure 1-1). It has
a maximum rate of fire of 850 rounds per minute. Primarily, ammunition is
fed into the weapon from a 200-round ammunition box containing a
disintegrating metallic split-link belt. As an emergency means of feeding,
the M249 AR can use a 20- or 30-round M16 rifle magazine, but this will
increase the chance of stoppages. Although the M249 AR is primarily used as
an automatic rifle, it is also used as a light machine gun. It can be fired
from the shoulder, hip, or underarm position; or from the bipod-steadied
position. When employed as a machine gun, it has a tripod with a T&E
mechanism and a spare barrel; however, barrels must not be interchanged with
those from other M249s unless the headspace has been set for that weapon by
direct support personnel.
Figure 1-1. M249 automatic rifle.
1-2. COMPONENTS
The major components of the M249 AR and their purposes are shown in
Table 1-1, and Figure 1-2. The sights and safety button
are discussed in paragraphs a and b and shown in Figures 1-3 and 1-4,
respectively. See Table 1-2, for general data.
Table 1-1. Components and purposes.
Figure 1-2. M249 AR components.
Table 1-2. General data.
a. Sights. The M249 AR has a hooded and semi-fixed 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 AR 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 equals 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.
Figure 1-4. M249 AR safety.
1-3. AMMUNITION
The M249 AR 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.
Figure 1-5. Cartridges for the M249.
- Type and Characteristics. The specific type ammunition ( Figure 1-5)
and its characteristics are as follows.
- Cartridge, 5.56-mm ball M855 (A059). The M855 cartridge has a
gilding, metal-jacketed, lead alloy core bullet with a steel penetrator. The
primer and case are waterproof. The ammunition is linked by a disintegrating
metallic split-linked belt for firing from the ammunition box (Figure 1-6).
In an emergency, the M855 round can also be loaded and fired from the M16
20or 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.
- Cartridge, 5.56-mm tracer, M856 (A064). This cartridge has a 63.7
grain bullet without a steel penetrator. It is identified by an orange tip.
The tracer is used for adjustments after observation, incendiary effects, and
signalling. 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.
- Cartridge, 5.56-mm dummy Ml99 (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 may 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.
- 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. An M15A2
blank-firing attachment must be used to fire this ammunition. (See
paragraph 1-4).
DANGER
Do not fire blank ammunition at any person within 20 feet, because
fragments of a closure wad or particles of unburned propellant can cause
injury.
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- Storage. Ammunition is stored under cover. If ammunition is in the
open, it must be kept at least 6 inches above the ground and covered with a
double thickness of tarpaulin. The cover must be placed so that it protects
the ammunition yet allows ventilation. Trenches are dug to divert water from
flowing under the ammunition.
- Care, Handling, and Preservation. Ammunition should not be removed
from the airtight containers until ready for use. Ammunition removed from the
airtight containers, particularly in damp climates, may corrode.
- Ammunition must be protected from mud, dirt, and moisture. If it
gets wet or dirty, the ammunition must be wiped off before using. Lightly
corroded cartridges are wiped off as soon as the corrosion is discovered.
Heavily corroded, dented, or loose projectiles should not be fired.
- Ammunition must be protected from the direct rays of the sun.
Excessive pressure from the heat may cause premature detonation.
- Oil should never be used on ammunition. Oil collects dust and other
abrasives that may possibly damage the operating parts of the weapon.
- Packaging. The ammunition can contains two plastic ammunition
boxes. Each box contains 200 rounds and weighs 6.92 pounds. Dummy
ammunition (M199) is packed in boxes of 20 rounds each.
1-4. BLANK FIRING AITACHMENT
The M15A2 BFA is the same attachment used for the M16 rifle.
a. Installation. The BFA is attached to the M249 AR by using the three
steps in Figure 1-7.
b. Care of the M249 While Using the BFA. A buildup of carbon inside
the weapon causes friction between the moving parts. Carbon deposits build
rapidly when blanks are fired. When these deposits become excessive,
stoppages occur. Therefore, keeping the weapon clean, especially the gas
system and chamber, during blank firing is very important. To get the best
performance with the BFA, the automatic rifleman performs the following:
- Inspects the weapon for damaged parts, excessive wear, cleanliness,
and proper lubrication before firing.
- When feasible, test fires the weapon using ball ammunition before
attaching the BFA.
- Adjusts the BFA to fit the weapon.
- Applies immediate action when stoppages occur.
- Cleans the gas system after firing 500 rounds.
- Cleans and lubricates the entire weapon after firing 1,000 rounds.
Figure 1-7. M15A2 BFA.
