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Inspection, Cleaning, and Lubrication

INSPECTION — CLEANING — LUBRICATION…

AFTER FIRING YOUR FIREARM, clean it as soon as possible to make the job easier and to avoid allowing the development of any corrosion.

When your Firearm has not been fired you should clean it at least once or twice a year if you live in a temperate climate, or as often as once a week in a tropical climate.

If you get your Firearm wet, clean it as soon as possible to avoid the onset of corrosion or rust.

Use a high quality Firearm cleaning kit that includes a cleaning rod; swab holder; cotton flannel bore patches; pipe cleaners; a small toothbrush; brass wire bristle bore and chamber brushes and a Cleaner/Lubricant/Preservative (CLP in Army terminology).

After you have disassembled the Firearm, thoroughly clean, inspect and lubricate all parts according to the techniques described on following pages.

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THE BUSHMASTER ACR IS DESIGNED TO OPERATE WITHOUT LUBRICATION AND AFTER CLEANING, ALL ACTION PARTS SHOULD BE WIPED DRY.

DETAILED CLEANING TECHNIQUES…

NOTE: The procedures below describe cleaning with a standard military issue type multi-piece rod cleaning kit. Other commercial cleaning kits may include alternate cleaning instructions which may be just as effective.

CLEANING THE BORE: The bore of your ACR rifle has Lands and Grooves called rifling. Rifling makes the bullet spin very fast as it moves down the Bore and down range. It is difficult to push a new, stiff Bore Brush through the Bore. You will find it much easier, and more effective, to pull your Bore Brush through the Bore. Also, because the brush will clean better if the bristles follow the grooves (this is called tracking), you want the Bore Brush to be allowed to turn as you pull it through.

To make cleaning the Bore easier, you may remove the barrel from the Upper and replace once the Bore and Chamber are cleaned. The zero of the barrel will not be lost.

ALWAYS CLEAN FROM THE CHAMBER TOWARD THE MUZZLE. Follow these steps:

  1. Attach three Rod Sections together but leave each one about two turns short of being tight. Attach the Patch Holder but leave it two turns short of tight also.
  2. Point Muzzle down. Hold the Upper Receiver or Barrel Assembly in one hand while inserting the end of the Rod with Patch Holder attached into the Chamber. Guide the Rod carefully through the Bore.
    CAUTION: Do not let the Rod or its threaded end scratch the Lining of the Bore or Firing Chamber. About 2 - 3 inches of the Rod should protrude out of the Muzzle.
  3. Attach the Handle Section of the Cleaning Rod to the end of the Rod sticking out of the Muzzle, and swab out the Bore with a patch moistened with “CLP”.
    ac-55-detailed-01.png
  4. Remove Patch Holder and attach Bore Brush (leaving it two turns short of tight).
  5. Pull the Brush through the Bore and out the Muzzle. You should be able to see the Rod twisting as you pull it - this is the Brush “tracking” in the rifling.
    NEVER reverse the direction of the Bore Brush while it is in the Bore.
  6. After one pull, take off the handle section and repeat the process. After three or four pulls, the three rod sections and the Bore Brush may become screwed tightly together. Loosen them up and repeat the process.
  7. Send a patch through the Bore occasionally to help clean out the crud that the brush is getting loose. Just replace the Bore Brush with the Rod Tip (Patch Holder) and a wet patch. Pull it through. If you leave the rods loose again, the patch will “track” in the rifling as before. But remember, always have the Bore wet with cleaner before trying to pull a brush through.

CLEANING THE GAS REGULATOR AND PISTON SYSTEM:

  1. Use Chamber Brush soaked with CLP to clean the inside of the Gas Block.
  2. Remove carbon and clean top of barrel just forward of the Gas Block where hot gas is ported out of the Gas Regulator.
    ac-56-detailed-02.png
  3. Wipe down Piston Rod and Piston Spring.
  4. Lubricate all parts and wipe dry.

CLEANING THE UPPER RECEIVER…

  1. Using a “CLP“ type product, clean all areas (inside and out) of Powder Fouling, Corrosion and Dirt.
    Never use a wire brush or any type of abrasive to clean the Aluminum Upper Receiver or Bearing Rails - you’ll scratch and damage the finish. A Toothbrush is good for loosening any dirt buildup, and won’t scratch the Receiver.
  2. Wipe all components clean and dry, and inspect for excessive wear, corrosion or mechanical damage. Have a qualified Gunsmith replace any worn or defective parts before firing again (or contact Bushmaster at 1-800-998-7928 for parts needs.)

CLEANING THE BOLT, BOLT CARRIER & COMPONENTS...

  1. Clean and inspect Bolt, Cam Pin, Firing Pin, Firing Pin Spring, Firing Pin Retaining Pin and Action Spring Assembly thoroughly.
    CHECK THE BOLT: Look for cracks or fractures, especially in the Cam Pin hole area. Inspect
    Bolt Face - Bolts with any pitting extending into the firing pin hole should be replaced.
    CHECK THE CAM PIN: If it is cracked, or chipped, it should be replaced. NOTE: Cam Pin can only be installed in Bolt from one  side - so Ejector will be positioned correctly.
    CHECK THE FIRING PIN: If it is bent, cracked, too blunted or too sharp, it should be replaced.
    CHECK THE FIRING PIN RETAINING PIN: If it is bent, or badly worn, it should be replaced. If O-ring is broken, worn or missing it should be replaced, though the Firearm will still function safely.
    ac-57-cleaning-01.png
    WIPE ALL PARTS DRY BEFORE REASSEMBLING BOLT CARRIER. WARNING: IF THE CAM PIN IS MISSING, DO NOT FIRE THE FIREARM – IT COULD MALFUNCTION CAUSING PROPERTY DAMAGE, PERSONAL INJURY OR DEATH.

CLEANING THE BOLT, BOLT CARRIER & COMPONENTS…

CHECK THE EXTRACTOR AND EXTRACTOR SPRING: If the Extractor is chipped, or has broken edges in the area of the lip that engages the cartridge rim, it should be replaced. Check that the rubber insert is inside the Extractor Spring. Clean off any Carbon buildup or powder residue.

CLEANING/LUBRICATING THE EJECTOR…

NOTE: The design of the Ejector makes its disassembly for cleaning somewhat impractical (i.e. we don’t recommend it). Make sure your Bushmaster ejects empty cases efficiently by following these steps on a monthly basis (more frequently if firing blanks).

  1. With the Bolt removed from the Bolt Carrier and the Extractor installed, hold it as shown, and dribble a few drops of CLP around the Ejector to form a puddle.
  2. Take a fired or dummy case and place it under the lip of the Extractor. With a rocking motion, press the case down against the Ejector. Since the Ejector is spring loaded, some resistance will be felt. Press on the case until it stops against the bolt face. Ease off with your thumb slightly and press down again. Repeat several times. Replace the CLP frequently. Once the spring action of the Ejector is smooth and strong, dry off any excess lubricant.
    ac-58-cleaning-02.png

CLEANING THE LOWER RECEIVER…

  1. Clean all areas of Powder Fouling, Corrosion, Dirt and Rust. Again, never use a wire brush or any type of abrasive to clean the proprietary composite polymer Lower Receiver.
    ac-59-cleaning-03.png
  2. Stocks may require cleaning as necessary and should be cleaned with mild detergent and water. Dry stock or let air dry after it has been cleaned.

REASSEMBLING YOUR FIREARM…

  1. Insert Piston Rod and Piston Spring through Gas Block and Piston Rod through Guide Block.
    ac-60-reassemble-01.png
  2. Insert Gas Regulator and rotate to either “U” or “S”
    ac-61-reassemble-02.png
  3. Attach the Barrel Assembly by guiding the Barrel Extension into the Trunnion. The piston will pass through an opening in the Trunnion.
    ac-62-reassemble-03.png
  4. Guide the Barrel Lock Handle to the right until it engages with the Trunnion. Once seated into the Trunnion, turn the barrel locking lever clockwise until there is a positive stop (you may have to depress the Barrel Plunger to start rotation). The Barrel Locking Ring will make audible clicks as the torque is being applied for proper installation.
    ac-63-reassemble-04.png
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  5. Install Hand Guard over the Barrel Assembly and push Hand Guard Retaining Pin closed to lock into place.
    ac-65-reassemble-06.png
  6. Insert Bolt into Bolt Carrier. Twist into position so Cam Pin can be inserted (remember Cam Pin can only be installed in Bolt from one side, so if it doesn’t fit right away, twist the Bolt 180° and try again).
    ac-66-reassemble-07.png
  7. Once Cam Pin is inserted, align the ridge on the head of the Cam Pin so it is parallel with the Bolt.
    WARNING: THE CAM PIN MUST BE INSTALLED IN THE BOLT GROUP. IF IT ISN’T, YOUR FIREARM CAN STILL FIRE AND COULD MALFUNCTION CAUSING PROPERTY DAMAGE, PERSONAL INJURY OR DEATH.
  8. Insert Firing Pin into Firing Pin Spring; Drop in and seat Firing Pin and Spring into Bolt Carrier.
    ac-67-reassemble-08.png
  9. Lightly press the Firing Pin into the Bolt Carrier; while holding, insert Firing Pin Retaining Pin.
    ac-68-reassemble-09.png
  10. Insert Action Spring Assembly into the Bolt Carrier by pressing inward (toward front of the Bolt) and twisting clockwise until the tabs on the front of the Action Spring Assembly Guide are in line with the Retaining Slot.
    ac-69-reassemble-10.png
    ac-70-reassemble-11.png
    ac-71-reassemble-12.png
    NOTE: The Recoil Lug at the back of the Action Spring Assembly should be pointing up toward the top of the Upper Receiver.
    NOTE: After inserting Firing Pin Retaining Pin, Firing Pin should not fall out when Bolt Carrier Assembly is turned upside down
    CAUTION: BUSHMASTER DOES NOT RECOMMEND THE PRACTICE OF SWAPPING BOLTS BETWEEN DIFFERENT FIREARMS. DOING SO COULD RESULT IN MALFUNCTION CAUSING PROPERTY DAMAGE, PERSONAL INJURY OR DEATH.
  11. Insert Bolt Carrier assembly into the Upper by aligning the notches on the Carrier with the Bearing Rails inside the Upper. Move forward until the locking lugs engage the Trunnion.
    ac-72-reassemble-13.png
  12. To join Upper and Lower Receivers, position Pivot Pin Lug of Upper Receiver into slot at front of Lower Receiver and push Pivot Pin into place.
    CAUTION: Always place the Safety Selector Lever on SAFE before pivoting the Upper Receiver to a closed position on the Lower Receiver.
  13. After Receivers are closed, push in Takedown Pin.
  14. To ensure proper reassembly, perform the safety function check prior to any attempt to fire the Rifle.

SLING REATTACHMENT…

If the Sling, or any other Accessories were removed for cleaning or maintenance, they should be reattached now.

MAGAZINE DISASSEMBLY/REASSEMBLY

  1. Unload Magazine fully.
  2. Turn Magazine base up. Push down and forward on Floorplate with a bullet head or other appropriate device.
    ac-73-reassemble-14.pngac-74-reassemble-15.png
    CAUTION: Floorplate is under pressure, so ensure care upon removal. Always wear eye protection.
  3. Pull gently on Magazine Spring and Follower to separate from Magazine body.
    ac-75-reassemble-16.png
  4. Wipe dirt from Body, Magazine Spring and Follower; then lightly lubricate Spring.
  5. Orient Follower and Magazine Spring to Magazine Body and carefully insert through bottom of Magazine Body.
  6. Slide Floorplate over lip on bottom of Magazine Body and continue sliding Floorplate over tabs until rear of Floorplate catches on Magazine Body.
    ac-76-reassemble-17.png

STOCK CHANGE

  1. Push the Rear Takedown Pin (a Bullet tip can help) as far as it will go. Pivot Upper Receiver from Lower Receiver.
    ac-77-stock-01.png
  2. Push the Stock Retaining Pin out.
    ac-78-stock-02.png
  3. Slide stock upward to separate from lower receiver.
    ac-79-stock-03.png
  4. Replace or insert new stock downward into cavity.
    ac-80-stock-04.png
  5. Push Stock Retaining Pin closed.
  6. Pivot Upper Receiver and Lower Receiver together and push Rear Takedown Pin closed.

HAND GUARD CHANGE

  1. Remove Hand Guard by pushing the Hand Guard Retaining Pin through as far as it will go and slide the Hand Guard forward.
    ac-81-hand-01.png
  2. Install alternate Hand Guard over the Barrel Assembly and push Hand Guard Retaining Pin closed to lock into place.
    ac-82-hand-02.png

CHARGING HANDLE

  1. Locate Charging Handle Release Button.
    ac-83-charging-01.png
  2. While using a punch or bullet tip, depress Release Button and slide to the rear while pulling the Charging Handle away from the Upper Receiver.
    ac-84-charging-02.png
  3. Still holding the Release Button to the rear, swap Charging Handle to the opposite side and re-insert or insert alternate Charging Handle.

CALIBER CONVERSION

  1. Remove Magazine.
  2. Unload and clear Firearm.
  3. Remove Hand Guard by pushing the Hand Guard Retaining Pin through as far as it will go and slide the Hand Guard forward.
  4. Lower the Barrel Locking Lever and depress the Barrel Plunger.
  5. With the Barrel Plunger depressed, turn the Barrel Locking Lever counter-clockwise until it stops.
  6. Pull the Barrel Assembly forward until it releases from the Trunnion.
  7. Remove the Bolt Carrier and disassemble (See Disassembling your Firearm).
  8. Select proper bolt head for caliber Firearm is being converted to.
  9. Install Bolt into Bolt Carrier.
  10. Reassemble Bolt Carrier.
  11. Ensure Bolt Carrier is removed from action or is locked to the rear.
  12. Select the proper barrel for the caliber rifle is being converted to.
  13. Guide the Barrel Extension into the Trunnion. The piston will pass through an opening in the Trunnion.
  14. Guide the Barrel Lock Handle to the right until it engages with the Trunnion. Once seated into the Trunnion, turn the barrel locking lever clockwise until there is a positive stop (you may have to depress the Barrel Plunger to start rotation). The Barrel Locking Ring will make audible clicks as the torque is being applied for proper installation.
  15. Install Hand Guard over the Barrel Assembly and push Hand Guard Retaining Pin closed to lock into place.
  16. Insert Bolt Carrier into the Upper by aligning the notches on the Bolt Carrier with the Bearing Rails inside the Upper. Move forward until the Locking Lugs engage the Barrel Extension.
  17. Select the proper Magazine and follow instructions for operating the Firearm (See Operation of Your Firearm).
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