This website is not affiliated with the U.S. government or military.

071-100-0004 (SL1) - Maintain an M4 or M4A1 Carbine

Standards: Cleaned, inspected, and lubricated the carbine and magazine so they functioned correctly. Cleaned and inspected the ammunition. Turned in any unserviceable ammunition.

Conditions: Given an M4 or M4A1 carbine, magazine, 5.56-mm ammunition, and small-arms accessory case with the following cleaning materials: clean wiping rags, bore brush, chamber brush, toothbrush, cleaning rod, small-arms swabs, pipe cleaners, cleaner lubricant and preservative (CLP), lubricating oil arctic weather (LAW), and carbine bore cleaner.

Standards: Cleaned, inspected, and lubricated the carbine and magazine so they functioned correctly. Cleaned and inspected the ammunition.  Turned in any unserviceable ammunition.

Performance Steps

1.   Clear the carbine.

a. Remove the magazine from the carbine, if there is one present.

b. Cock the carbine.

c. Turn the selector to SAFE.

Note. The selector cannot be turned to SAFE unless the carbine is cocked.

d. Lock the bolt open.

(1)  Pull the charging handle rearward.

(2)  Press the bottom of the bolt catch.

(3)  Allow the bolt to move forward until it engages the bolt catch.

(4)  Return the charging handle to the forward position.

(5)  Ensure the selector is on SAFE.

e. Check the receiver and chamber to ensure they do not contain ammunition.

2.   Disassemble the carbine.

CAUTION: Do not use a screwdriver or any other tool when removing the handguards. Doing so may damage the handguards, slip ring, or both.

WARNING: Use care not to bend or dent the gas tube while removing handguards

a. Remove the sling.

b. Remove the handguards if you can see dirt or corrosion through the vent holes. Handguards are interchangeable because they are identical.

CAUTION: Use only hand pressure to disengage the pivot and takedown pins. Force other than hand pressure may cause damage to the weapon so replacement of the weapon is required. Push the pivot and takedown pins only far enough to disengage the upper receiver from the lower receiver.

c. Push the takedown pin as far as it will go and pivot the upper receiver from the lower receiver.

d. Push the receiver pivot pin.

e. Separate the upper and lower receivers.

f.  Pull back the charging handle.

g. Remove the bolt carrier and bolt.

h. Remove the charging handle.

CAUTION: Do not fully remove the round nuts from the threaded studs. The threaded studs are flared on the end to prohibit removal. However, if the nuts are inadvertently removed, they may be reinstalled.

i.   Remove carrying handle assembly. Loosen the round nuts on the left side of the carrying handle approximately four turns. Loosen the clamping bar from the left side of the upper receiver and lift off the carrying handle.

j.   Remove the firing pin retaining pin.

k. Put the bolt assembly in the locked position by pushing in the bolt.

l.   Remove the firing pin by allowing it to drop out of the rear of the bolt carrier into your hand.

m.   Remove the bolt cam pin by turning it one-quarter turn and lifting it out.

n. Pull the bolt assembly from the carrier.

Note. Perform steps o through q only when the parts are dirty or damaged.

o. Press the rear of the extractor pin to check spring function. Report any weak springs to unit armorer for replacement.

p. Remove the extractor pin by pushing it out with the firing pin (use care not to damage the firing pin).

q. Lift out the extractor and spring, taking care that the spring does not separate from the extractor.

r.  Release the buffer by pressing the buffer and depressing the retainer.

s. Remove the buffer and action spring separating the buffer from the spring.

t.  Extend the buttstock assembly to full open. The M4/M4A1 has a four-position buttstock: closed, 1/2 open, 3/4 open, and full open.

u. Grasp the lock lever in the area of the retaining nut, pull downward, and slide the buttstock to the rear to separate the buttstock assembly from the lower receiver extension.

3.   Clean the carbine.

a. Upper receiver group.

(1)  Use small-arms swabs, CLP, and bore brush to clean bore.

(2)  Use rags, cleaning brush, and CLP to remove powder fouling, corrosion, dirt, and rust from other areas.

(3)  Clean bolt lugs with CLP and chamber brush.

(4)  Use CLP and bore brush to clean barrel locking lugs and gas tube.

b. Lower receiver group.

(1)  Remove powder fouling, corrosion, and dirt with rags, cleaning brush, and CLP.

(2)  Clean buffer tube and buttstock tube with rag attached to holder.

(3)  Clean buffer action spring and inside lower receiver extension with brush and rags.

c. Bolt carrier group.

(1)  Clean outer and inner surfaces of bolt carrier with rags and CLP.

(2)  Clean carrier key (use worn bore brush).

(3)  Clean firing pin recess and firing pin with brush and CLP.

(4)  Clean firing pin hole with pipe cleaner and CLP.

(5)  Clean carbon deposits and dirt from locking lugs with cleaning brush and CLP.

(6)  Clean areas behind bolt ring and under lip of extractor with brush and CLP.

4.   Inspect carbine for serviceability.

a. Upper receiver group.

(1)  Check for free movement of the forward assist assembly.

(2)  Check for broken or damaged ejection port cover.

(3)  Check rear sight windage and elevation knob for damage and looseness.

(4)  Check carrying handle assembly for missing or damaged parts and ensure the handle assembly will mount to the upper receiver.

(5)  Check front sight assembly for damage.

(6)  Inspect bore and chamber for pitting or obstructions.

(7)  Inspect bolt lugs for cracks and burrs.

(8)  Check for free movement of slip ring.

(9)  Check the compensator for proper alignment.

Note. The compensator has five slots. The third or middle slot should line up with the front sight post. If not, turn the compensator in for maintenance.

(10) Check the bolt guide rails for chips and burrs.

b. Lower receiver.

(1)  Check trigger mechanism for missing or damaged parts.

(2)  Check bolt catch for free movement.

(3)  Check magazine release button for free movement.

(4)  Check buttstock assembly for dents and rust and ensure proper operation of retaining nut and lock-release lever.

(5)  Check action spring and buffer for damage.

c. Bolt carrier group.

(1)  Check bolt carrier for chips, burrs, and cracks.

(2)  Check bolt for cracks or fractures, especially in the cam pin hole area. Bolts that contain pits in the firing pin hole need replacing.

(3)  Check firing pin retaining pin for bends and excessive wear.

(4)  Check firing pin for bends, cracks, and blunted or sharp end.

(5)  Check cam pin for cracks and chips.

(6)  Check extractor for chipped or broken edges in the area of the lip that engages the cartridge rim. Check to ensure the rubber insert is inside the extractor spring.

d. Report and turn in unserviceable parts for maintenance.

5.   Lubricate the carbine.

Note.   Under all but the coldest arctic conditions, CLP is the lubricant to use on the carbine. Between +10 degrees Fahrenheit and -10 degrees Fahrenheit, either CLP or LAW can be used. For -35 degrees Fahrenheit or lower, use LAW only.

Note.   Lightly lube means apply a film of lubricant barely visible to the eye.

Note.   Generously lube means apply the lubricant heavily enough so it can be spread with the finger.

a. Upper receiver and carrying handle.

(1)  Upper receiver. Lightly lube inside of receiver, bore, chamber, locking lugs, outer surfaces of barrel and front sight, and mating surface for carrying handle.

(2)  Carrying handle. Apply a drop or two of lubricant to both threaded studs. Lightly lube the clamping bar and both round nuts. Lightly lube the mating surface.

(3)  Front sight detent. Depress and apply two or three drops of CLP to front sight detent. Depress several times to work lube into the spring.

(4)  Adjustable rear sights. Use one or two drops of CLP. Rotate the following parts to ensure lubricant is spread evenly above and below:

(a) Elevation screw shaft.

(b) Elevation knob.

(c) Windage knob.

(d) Windage screw.

b. Lower receiver group.

(1)  Lightly lube inside and outside lower receiver extension, buffer, and action spring. Lightly lube inside buttstock assembly. Generously lube buttstock lock-release lever and retaining pin.

(2)  Generously lube takedown pin, pivot pin, detents, and all other moving parts and their pins.

c. Bolt carrier group.

(1)  Lightly lube charging handle and inner and outer surfaces of bolt carrier.

(2)  Place one drop of CLP in the carrier key.

(3)  Apply a light coat of CLP on firing pin and firing pin recess in bolt.

(4)  Generously lube outside the bolt body, bolt rings, and cam pin area.

(5)  Apply a light coat of CLP on extractor and pin.

6.   Assemble the carbine.

a. Install buttstock assembly. Align the buttstock assembly with lower receiver extension; pull downward on the lock release lever near the retaining pin, and slide the buttstock assembly onto the lower receiver extension.

b. Insert action spring and buffer.

c. Insert extractor and spring.

d. Push in extractor pin.

e. Slide bolt into carrier.

WARNING: Be sure the cam pin is installed in the bolt group. If it is not, the carbine can still fire and will explode.

f.  Replace bolt cam pin.

g. Drop in and seat firing pin.

h. Pull bolt back.

i.   Replace retaining pin.

j.   Engage, then push charging handle in part of the way.

WARNING: Do not exchange or switch bolt assemblies from one M4 or M4A1 to another.

k. Slide in bolt carrier group.

l.   Push in charging handle and bolt carrier group together.

m.   Join upper and lower receivers.

n. Engage receiver pivot pin.

o. Close upper and lower receiver groups. Push in takedown pin.

p. Replace handguards.

q. Replace sling.

7.   Perform a function check on the M4 or M4A1 carbine to determine correct functioning according to Task 071-100-0005.

8.   Maintain M16/M4 magazine and ammunition.

a. Maintain magazine.

(1)  Disassemble magazine.

  • Insert the nose of a cartridge into the hole in the base of the magazine and raise the rear of the magazine until the indentation on the base is clear of the magazine.
  • Slide the base forward until free of the tabs.
  • Remove the magazine spring and follower (do not separate).

(2)  Clean all parts using a rag soaked with CLP. Dry all parts.

(3)  Inspect parts for damage such as dents and corrosion. If any damage is found, turn in to maintenance.

(4)  Lubricate the magazine. Lightly lube the spring only.

(5)  Assemble the magazine.

  • Insert the follower and spring in the magazine tube and jiggle the spring to seat them in the magazine.
  • Slide the base under all four tabs until it is fully seated. Make sure the printing is on the outside.

b. Maintain ammunition.

(1)  Clean ammunition with a clean dry rag.

(2)  Inspect  and turn in any ammunition with the following defects: corrosion, dented cartridges, cartridges with loose bullets, and cartridges with the bullet pushed in.

Evaluation Preparation: 

Setup: Have soldiers use their own weapons and magazines. Provide swabs, cleaner, lubricant, preservative (CLP), pipe cleaners, lubricating oil, and rifle bore cleaner (the soldier should not select rifle bore cleaner for use). Also provide several rounds of dummy ammunition, if available.

Brief Soldier: Tell the soldier to clean, inspect, and lubricate the weapon and magazine following normal safety practices.

Performance Measures



1.   Cleared the carbine.



2.   Disassembled the carbine.



3.   Cleaned the weapon using the correct materials.



4.   Inspected for unserviceable parts.



5.   Assembled the carbine.



6.   Performed a function check.



7.   Disassembled the magazine.



8.   Cleaned the magazine.



9.   Assembled the magazine



10. Cleaned the ammunition.



Evaluation Guidance:  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 correctly.







TM 9-1005-319-10