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071-025-0001 (SL1) - Maintain an M240B Machine Gun

Standards: Cleaned and lubricated the M240B machine gun and components. Inspected all parts, components, and ammunition for serviceability; turned in unserviceable items to maintenance. Correctly assembled the gun and ensured it was operational.

Conditions: Given a cleared M240B machine gun; M122A1 tripod mount
assembly; linked 7.62-mm ammunition; and a
small-arms case with the following items:
cleaner, lubricant, and preservative (CLP),
lubricating oil arctic weather (LAW), rifle
bore cleaner (RBC), rags, pipe cleaners,
chamber and bore brushes, cleaning rod,
cleaning rags, small-arms swabs, and an
M240B scraper and reamer.

Cleaned and lubricated the M240B machine gun
and components. Inspected all parts,
components, and ammunition for
serviceability; turned in unserviceable
items to maintenance. Correctly assembled
the gun and ensured it was operational.

Performance Steps

1.   Check to ensure the weapon is clear.

Be sure to
clear weapon before disassembling,
cleaning, inspecting, transporting,
or storing.

Put safety to "F"

Pull cocking handle
assembly to the rear, locking the bolt
to the rear. Return cocking handle to
forward position.

Place safety to
"S" (SAFE).

Push in latches to open
cover assembly.

Remove ammunition belt, if

Raise feed tray.

Inspect chamber area.
Remove any ammunition, ammunition
casings, or links.

Check feed pawl assembly
and feed tray assembly.

Lift feed tray assembly and
inspect the chamber.

Check space between the
face of the bolt and the chamber.

Check space under the bolt
and operating rod assembly.

Lower feed tray.

Place safety to

Hold cocking handle
assembly to rear, depress trigger, and
ease bolt forward to close and lock.

Close cover assembly. Make
sure it locks shut.

Note. Be sure bolt is forward with safety in "F"
when gun is not in use.

2.   Disassemble the M240B.

A hot barrel
can burn you. If the barrel is hot,
use your heat resistant mittens

Note. The following steps do not have to be performed in

Remove barrel assembly.

Check to ensure bolt is

Depress barrel locking
latch and hold.

Turn barrel carrying handle
to upright position.

Push forward and lift
barrel out.

Remove heat shield assembly
from barrel. Lift rear of heat shield
assembly from barrel; pry front tabs
out of holes on gas hole bushing.

Remove trigger-housing

Depress spring pin and
remove it (this can usually be done
without tools).

Pull trigger-housing
assembly down and back, and remove it.

Remove butt stock and
buffer assembly. Depress backplate
latch and lift butt stock and buffer
assembly straight up.

Remove driving spring rod

Push driving spring rod
assembly forward and up to disengage
its retaining stud from the receiver.

Pull rearward on driving
spring rod and remove it from the

Remove bolt and operating
rod assembly.

Depress cover latches and
raise cover assembly.

Pull cocking handle
assembly back to move bolt and
operating rod assembly to the rear of

Reach into receiver and
push rearward on bolt until bolt and
operating rod assembly are slightly
out of rear end of receiver.

Grasp bolt and operating
rod assembly and remove it from the

Return cocking handle to
forward position.

Remove cover assembly.

Close cover.

Push out spring pin as far
as possible using backplate of the
butt stock or buffer assembly. Then
remove it with your fingers.

Depress cover latches, lift
up, and remove cover assembly.

Remove feed tray.

Remove hand guard.

Extend bipod legs to down
and locked position.

Pull hand guard straight
down and off gas cylinder.

gasoline, kerosene, hydraulic oil,
benzene, benzol, high pressure
water, steam, or air for cleaning is

3.   Clean the M240B parts, components, and ammunition.


1. Do not use
abrasives to clean the bore, piston,
gas cylinder, or gas regulator plug.

2. Do not
submerge buffer in any liquid. Wipe
with clean wiping rag only.

3. Avoid getting
CLP in the gas cylinder when
cleaning the bore.

Use cleaning patches, CLP,
and bore brush to clean bore.

Use CLP on receiver brush
bristles to clean the receiver.

Use rags and CLP to remove
powder fouling, corrosion, dirt, and
rust from all metal components and

Use only a clean rag to
clean the cover assembly.

Clean the gas cylinder.

Use a gas cylinder cleaning
brush dampened with CLP to clean gas
cylinder bore.

Use a combination tool to
clean front interior of gas cylinder.

Insert the combination tool
with handle upward into the front end
of the gas cylinder of the receiver
body. Ensure the tool is fully
inserted and seated against the gas

Apply slight pressure to
the handles and turn clockwise to
remove carbon.

Clean gas regulator using
the scraper and reamer.

Insert the scraper into the
central hole of the gas regulator
plug. Remove carbon by twisting the
scraper clockwise until it is fully
seated against gas regulator plug.

Clean regulator plug
grooves by inserting the scraper tool
into the grooves and turning regulator
plug clockwise.

Insert the small reamer
into each gas inlet hole and twist
back and forth to remove carbon (use
hand pressure only).

Scrape carbon from surface
of gas regulator plug using tip of

Insert large reamer through
hole in gas port bushing into gas port
hole in barrel; remove carbon by
twisting reamer back and forth until
it enters bore of barrel.

Clean M122A1 tripod

T&E mechanism. Use a
clean dry wiping rag to remove foreign
matter. Use small arms cleaning brush
to clean numbers on the scale.

Tripod assembly and flex
mount. Use a cleaning rag saturated
with carbon-removing compound to clean
them with clean wiping rags to wipe
all parts dry.

Clean Ammunition. Use a
clean dry wiping rag to remove foreign

4.   Inspect the M240B parts, components, and

Barrel assembly.

Check barrel for bulges,
bends, burrs, or pits in the chamber
or bore.

Check to ensure flash
suppressor is not loose.

Check front sight for
damage and looseness.

Check barrel carrying
handle assembly for damaged or missing
parts. Move the barrel release slowly
to the right and count the clicks.
Fewer than two, or more than seven
clicks indicate defective parts.

Check to ensure heat shield
is present, securely attached to
barrel, and undamaged.

Butt stock and buffer

Check for burrs and rough
edges on the mating grooves and

Check the backplate latch
to ensure it locks the buffer assembly

Check the buffer plug and
ensure it sticks out through the
backplate and is flush or higher than
the protrusion below it.

Check the buffer for
rattling sounds by shaking; ensure
that the plug cannot rotate by finger

Check the butt stock for

Driving spring rod

Check the spring for broken

Check the rod assembly for

Bolt and operating rod

Inspect the bolt and
operating rod assembly for bent,
broken, cracked or missing parts.
Check for burrs or pits on the

Check for cracks or wear on
the tip of the firing pin.

Ensure you cannot move
extractor with your fingers.

Trigger-housing assembly

Check for broken, missing,
or damaged parts.

Inspect the tripping lever
and sear for burrs on edges.

Check cocking action by
pushing back on the tripping lever
(sear will rise). Pull the trigger
(sear will lower).

Check safety. Place on
"S" (SAFE) and pull the
trigger. The sear should not drop down
far enough to lock in the downward
position. Place the safety on
"F" (FIRE) and pull the
trigger. The sear should drop down and
lock in the downward position.

Cover assembly.

Pivot the feed lever back
and forth to ensure it operates
smoothly without binding.

Push in on the cover
latches to make sure the retaining
clip is present, secure, and does not
bind in the housing.

Push down on the cartridge
guides and feed pawls to make sure the
springs are present and secure.

Inspect accessory-mounting
rail for nicks or burrs.

Feed tray. Check for
cracks, deformation, broken welds, and
loose rivets.

Hand guard. Check for
cracks and broken or missing parts.

Receiver assembly.

Check that the rear sight
is securely mounted and operates

Check that the cocking
handle operates properly.

Check for damaged or
missing ejection port cover, spring,
and pin. Check for proper operation of
ejection port cover.

Lower and raise the bipod
legs to ensure they move freely
without binding.

Check accessory-mounting
rail for nicks or burrs that may
prevent proper attachment of optional
sighting devices.

Check barrel locking latch
and cover detent for proper spring


T&E mechanism.

Inspect hand wheels for
smooth operation or rust.

Check threads for burrs and

Check traversing slide lock
for spring action. Ensure elevating
mechanism sleeve fits on traversing
bar and clamps firmly.

Check traversing and
elevating scales for legibility.

Inspect quick release pin
and chain for burrs and rust. Check
for missing spring-loaded balls.

Tripod assembly.

Check for completeness of
tripod. Ensure that all nuts and bolts
are tightly secured.

Inspect for cracks on the
legs and tripod head.

Check for missing, broken,
or inoperative lock latch.

Check pintle lock release
cam for correct operation.

Check locking action of
front leg clamping assembly.

Check that the rear legs
lock in the open position. Ensure
sleeve latch notch and right leg slide
notch engages completely. Ensure latch
spring has good tension.

Check telescoping,
indexing, and locking action of rear
legs and front leg locking assemblies.

Flexible mount assembly.

Check for missing or
damaged parts. Check for rust, cracks,
and burrs.

Inspect pintle lock
assembly for nut, bolt, and cotter
pin. Check pintle surface for burrs
and rust.

Inspect or check ammunition
for damage and corrosion. Turn in any
unserviceable ammunition.

5.   Lubricate M240B parts and components.

Generously lube the
following parts:

Barrel assembly-on the
camming surfaces of the bolt-locking

Operating rod-on the
rollers, camming recess, and those
surfaces immediately below the yoke
that ride within the receiver rails.

Cover-in the feed cam

Bolt-on the bolt-locking
lugs and actuator cam roller.

Lightly lube the following

Driving spring.

Bolt and operating rod
assembly moving parts, polished areas,
firing pin, and roller.

Do not lubricate the
following parts:

Butt stock.

Face of bolt.


Gas regulator and gas

Rear sight.

Composite or rubber

Lightly lubricate all
components and wipe with oily rag to
remove excess oil.

6.   Assemble the M240B.

Replace barrel assembly.

Insert gas regulator plug
into the gas hole bushing with the
number 1 gas setting facing the

Place gas collar over the
front end of the gas regulator plug.
Rotate collar until it slips onto gas
regulator plug. Press in and rotate
counterclockwise to lock in place
(pull collar to be sure it is in the
locked position).

Install heat shield on
barrel. Insert the front metal tabs of
the heat shield into the holes located
on the sides of the gas hole bushing.
Push down on the heat shield so it
snaps onto the barrel.

With gas regulator downward
and the carrying handle in the
vertical position, insert barrel fully
into the receiver socket and push
barrel carrying handle to the right as
far as it will go to lock (fewer than
two or more than seven clicks indicate
defective parts). Do not force. If
barrel binds in socket or if barrel
carrying handle will not rotate when
pushed, do not pound on barrel
carrying handle. Take machine gun to
unit maintenance.

Replace cover assembly and
feed tray.

Align the feed tray guides
with receiver brackets.

Place cover assembly onto
the receiver with its mounting holes
aligned with mounting brackets on the

Close cover assembly. To
secure the cover and feed tray to the
receiver; insert the spring pin in the
mounting holes from the right side
only. Open cover assembly. Check to
ensure cover detent holds cover
assembly open. If cover assembly does
not remain open in two positions,
notify unit maintenance.

Replace trigger-housing

Insert the holding notch on
the trigger-housing into the forward
recess on the bottom of the receiver.

Lift the trigger-housing up
and align holes of trigger-housing
with the mounting holes of the

Hold the trigger-housing in
place and insert the spring pin.

Replace bolt and operating
rod assembly.

Insert the bolt and
operating rod assembly into the rear
of the receiver. Ensure bolt is on top
of receiver rails.

Push the assembly into the
receiver as far as possible. Pull the
trigger and hold it while pushing the
assembly all the way into the

Close cover assembly.

Replace the driving spring
rod assembly.

Insert driving rod spring
assembly all the way into the

Push in and lower driving
rod spring assembly to seat the
retaining stud in the hole on the
bottom of the receiver.

Replace butt stock and
buffer assembly.

Position the bottom recess
grooves of the butt stock onto the top
of the receiver recess grooves.

Slide the butt stock down
until it locks on the receiver. Top of
buffer should be flush with top of

7.   Perform a function check to ensure the M240B is
assembled correctly.

Evaluation Preparation: 

Setup: At the test site, provide all the equipment and materials
listed in task conditions. Use only dummy
ammunition for training purposes.

Soldier: Tell soldier to perform
maintenance on the M240B and linked 7.62-mm




1.   Checked to ensure the weapon was clear.

2.   Disassembled the M240B.

3.   Cleaned the M240B parts, components, and

4.   Inspected the M240B parts, components, and

5.   Lubricated M240B parts and components.

Score the soldier GO if all
performance measures are passed. Score the
soldier NO GO if any performance measure is
failed. If the soldier scores NO GO, show
him what was done wrong and how to do it