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Components of the M249 Machine Gun

Major Components, Sights and Safety with photos
1. Barrel
Houses cartridges
for firing, directs projectile, and supports the gas regulator.
2. Heat shield
protection for the gunner’s hand from a hot barrel.
3. Rear sight
Adjusts for both
windage and elevation.
4. Cover and feed
mechanism assembly
Feeds linked belt
ammunition, and positions and holds cartridges in position for stripping,
feeding, and chambering.
5. Feed tray
Positions belted
ammunition for firing.
6. Cocking handle
Pulls the moving
parts rearward. Moves in a guide rail fixed to the right side of the
7. Buttstock and
buffer assembly
Contains a
folding buttplate. Serves as a shoulder support for aiming and firing M249.
Contains a folding shoulder rest and a hydraulic buffer to absorb the
8. Bolt assembly Provides feeding,
stripping, chambering, firing, and extraction, using the projectile gases
for power.
9. Slide assembly Houses firing pin
and roller assembly.
10. Return rod
and transfer mechanism assembly
Absorbs recoil
for bolt and operating rod assembly at the end of recoil movement.
11. Receiver
Serves as a
support for all major components and houses action of weapon. Through a
series of cam ways, controls functioning of weapon.
12. Trigger
Controls the
firing of the weapon. Provides storage area for lubricant in grip portion.
13. Handguard
Provides thermal
insulation to protect the gunner’s hand from heat or extreme cold and houses
the cleaning equipment.
14. Sling and
snap hook assembly
Provides a means
of carrying the weapon.
15. Bipod Supports the M249
machine gun in the prone position. The telescopic legs can be individually
adjusted to three different lengths.
16. Gas cylinder assembly Locks bipod in
place and provides passageway for gases.
17. Piston assembly Holds the bolt
and slide assemblies and houses the return spring.
18. Return spring Returns bolt,
slide, and piston assemblies to locked position during counterrecoil cycle.
19. Tripod (M122) (Not shown) The tripod and T&E mechanism, with pintle, provides a stable
mount and permits a higher degree of accuracy and control.
20. M145 straight telescope
(Not shown)
Machine gun optic (MGO)
provides target acquisition and identification at greater ranges.

M249 Machine Gun Components

Sights.  The M249 machine gun has a hooded and semifixed front sight. 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 onehalf- 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-halfmil 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.

M249 Machine Gun Sights

Safety.  The
safety 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.

M249 Machine Gun Safety