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User Manual

ABOUT YOUR BUSHMASTER RIFLE…

This Operating Manual covers the Bushmaster ACR (“ACR”) which is chambered in 5.56mm NATO/223 Remington and 6.8mm Remington SPC ammunition. It is a gas piston, air-cooled shoulder fired, magazine-fed Firearm, that is Semi-Automatic in operation (i.e., a single round will fire each time the trigger is pulled).

  • The ACR Barrels are cold hammer forged and hold the tightest tolerance allowed. They are rifled with either a 1 turn in 7” for heavier grain weight bullets or 1 turn in 9” for lighter bullets with a right hand twist – 6 lands and grooves.
  • The ACR is operated by a regulated, short-stroke Gas Piston System which eliminates hot gas from being introduced into the Upper and Lower Receivers. The Regulator can be set for Unsuppressed or Suppressed fire.
  • The ACR is a multi-caliber platform and is capable of transitioning to a range of calibers simply by swapping the Barrel Assembly and Bolt, using the appropriate Magazine. Some calibers may require an alternate lower to accept different sized Magazines.
  • All ACR Upper and Lower Receivers are easily opened for cleaning and inspection.
  • The Upper Receiver is made of extruded Aluminum and the Lower Receiver is made of a proprietary composite polymer.
  • Most ACR models feature fully adjustable rear sights/elevation adjustable front sights.
  • The Bolt Group locks into the Barrel Extension with 7 locking lugs.
  • All models can be configured with either a Fixed Stock or 7 position Telescoping/Folding Stock.
  • All models feature vertical pistol grips and detachable magazines. Magazine capacity is 30 rounds standard (depending on State Regulations), but all AR-15/M-16 type magazines of capacities from 5 to 40 rounds will fit the ACR and function in it.

Firearm Features & Controls - Identification/Location…

ac-01-firearm-01.png

ac-02-firearm-02.png

NOTE: ATF Regulations require a minimum barrel length of 16" on commercially available rifles and carbines. This 16" length can be a combination of barrel and permanently fixed (pinned & welded over) muzzle brake/flash suppressor as long as total length equals 16".

CLEARING YOUR FIREARM…

ALWAYS FOLLOW THE RULES OF SAFE FIREARM HANDLING. First, assume the firearm you are handling is loaded, and then proceed - according to the following steps - to CLEAR YOUR FIREARM . . .

  1. Point Firearm in a SAFE DIRECTION! Place Safety Selector Lever on SAFE.
    ac-03-clearing-01.png
    NOTE: If the Firearm is not cocked, the Safety Selector Lever cannot be pointed toward SAFE.
  2. Press Magazine Release Button and pull Magazine down to remove.
  3. To lock Bolt open, pull Charging Handle rearward. Press upward on the Bolt Catch and allow Bolt to move forward until it engages the Bolt Catch. If you haven’t before, now place Safety Selector Lever on SAFE.
    ac-04-clearing-02.png
  4. Visually and physically check that the Chamber is clear.

PREVENTATIVE MAINTENANCE CHECKS & SERVICES…

CHECK BEFORE YOU FIRE!

ALWAYS FOLLOW THE RULES OF SAFE FIREARM HANDLING.

First, assume the Firearm you are handling is loaded, and then proceed - according to the following steps - to CLEAR YOUR FIREARM...

  1. Check to see that there is NO EXCESSIVE OIL in the Bore. If there is, swab it out with a patch and the cleaning rod. ALWAYS CLEAN A NEW FIREARM BEFORE FIRING.
    WARNING!
    If the Firearm is fired with oil - or water - in the barrel, excessive pressure will be created and the Firearm could malfunction causing personal injury, property damage or death.
  2. Retract the Bolt to ensure free movement of the Bolt Carrier.
    ac-05-preventative-01.png
  3. Perform Safety Function Check to ensure that Safety Selector Lever works properly.
  4. Ensure the Gas Regulator is set to “U” for unsupressed fire; if firing with a silencer mounted, set Gas Regulutor to “S” for suppressed fire.
    ac-06-preventative-02.png
    NOTE: Gas Regulator must be set correctly for either unsuppressed or suppressed fire; If not set correctly the Firearm could  malfunction causing personal injury, property damage or death.
    WARNING! Never operate Firearm with Gas Regulator set in between the “U” and “S” settings.

SAFETY FUNCTION CHECK…

UNLOAD FIREARM - REMOVE MAGAZINE - CHECK CHAMBER

  1. Remove Magazine if installed. Pull Charging Handle assembly to rear. Check that Chamber is clear. Let the Bolt and Bolt Carrier close. Do not pull Trigger. Leave Hammer in cocked position.
    WARNING! If Firearm fails any of the following tests, continued use of the Firearm could cause a malfunction causing personal injury, property damage or death.
  2. Place Selector Lever in SAFE position, point rifle in a safe direction, and pull the Trigger. THE HAMMER SHOULD NOT FALL.
    ac-07-safety-01.png
  3. Place Selector Lever in FIRE position. Pull the Trigger.
    THE HAMMER SHOULD FALL.
    ac-08-safety-02.png
    NOTE: For purposes of the following check, “SLOW” is defined as one fourth to one half the normal rate of trigger release.
  4. Hold Trigger to the rear, pull Charging Handle to the rear and release Charging Handle. Then release pressure on the Trigger with a slow, smooth motion, without hesitations or stops, until the Trigger is fully forward.
    AN AUDIBLE CLICK SHOULD BE HEARD - THE HAMMER SHOULD NOT FALL.
  5. Repeat the FIRE position test FIVE TIMES. The Firearm must not malfunction during any of these five tests. Pull the Charging Handle to the rear one last time and release forward.
  6. Place the Selector Lever in SAFE position. Pull the Trigger.
    THE HAMMER SHOULD NOT FALL.
    If the Firearm malfunctions during any of these five tests, have the Firearm checked by a qualified gunsmith.

PREPARING TO FIRE - LOADING A MAGAZINE…

  1. Use only quality 5.56mm/223 Remington Ammunition in your Firearm (or 6.8mm Remington SPC if applicable). Examine each Cartridge - particularly around the primer. Look for dents, scratches, and other signs of damage.
    DO NOT LOAD DAMAGED AMMUNITION!
  2. With the Magazine facing forward, as shown in the illustration, place a Round between the Feed Lips of the Magazine with the Bullet Tip forward. Push the Round down until it is held by the Magazine Feed Lips.
  3. If necessary, give the Round a slight push backward to seat it against the inside back edge of the Magazine Feed Lips. Place next Round on top of the previous Round and repeat steps until desired number of Rounds are loaded into Magazine.
    CAUTION! Safe Firearms Handling dictates that you ONLY LOAD LIVE AMMUNITION INTO YOUR RIFLE WHEN YOU ARE ABOUT TO SHOOT.

OPERATION OF YOUR FIREARM… LOADING

CAUTION: ALWAYS POINT THE MUZZLE IN A SAFE DIRECTION!

  1. With the Hammer cocked, place Selector Lever on SAFE.
    ac-09-operation-01.png
  2. Open Bolt and check Firing Chamber. Make sure it is CLEAR!
    ac-10-operation-02.png

INSERTING A MAGAZINE…

  1. Return Charging Handle to forward, locked position. Push Magazine up into Magazine Well until Magazine Catch engages and holds the Magazine.
    ac-11-inserting-01.png
  2. Slap upwards on Magazine bottom to make sure it is seated correctly.
    ac-10-operation-02.png

CHAMBERING A ROUND FROM AN OPEN BOLT…

NOTE: The Magazine may be inserted into the Firearm with the Bolt Assembly Open or Closed.

  1. Press the Bolt Catch downward. Bolt should spring forward. This will chamber a round from the Magazine.
    ac-13-chambering-01.png
  2. TAP the Charging Handle forward with the heel of your hand to ensure that the Bolt is fully forward and locked.
    ac-14-chambering-02.png
    FIREARM IS NOW READY TO BE AIMED AND FIRED!

CHAMBERING A ROUND FROM A CLOSED BOLT…

  1. With a Magazine in the Firearm, pull the Charging Handle fully to Rear. Then release the Charging Handle – allowing the Bolt to spring forward – chambering the first round.
    NEVER “Ride” or push the Charging Handle forward. Let it move forward on its own.
    ac-15-chambering-03.png
  2. TAP the Charging Handle forward to ensure that the Bolt is fully forward and locked.
    ac-16-chambering-04.png
    FIREARM IS NOW READY TO BE AIMED AND FIRED!
    NOTE: If Firearm is not going to be fired immediately, make sure the Selector Lever is still on SAFE.

CONDITION: Firearm is now Loaded, a Round is chambered, and Safety Selector should be on SAFE.

CAUTION: ALWAYS POINT THE MUZZLE IN A SAFE DIRECTION!

To FIRE the Firearm in SEMI-AUTOMATIC MODE (one Round fired with each pull of the Trigger), move the Safety Selector Lever from SAFE to FIRE.

ac-17-operation-01.png

Aim at Target – Pull Trigger – Release.

The Firearm will automatically eject the spent Cartridge and chamber another Round in preparation for the next shot. The cycle of pulling the Trigger to shoot, and the Firearm automatically reloading, can be continued until the Magazine is empty.

NOTE: After the last Round is fired, the Bolt Carrier will lock in the rear position. You can then push the Magazine Release Button to drop out the empty magazine, insert a fresh Magazine, release the Bolt Catch, and a new Round will be automatically chambered in
preparation for the next firing sequence.

WARNING… IF A NOTICEABLE DIFFERENCE IN SOUND OR RECOIL IS EXPERIENCED, STOP FIRING AND IMMEDIATELY CHECK THE FIREARM FOR OBSTRUCTIONS. AN OBSTRUCTION MAY CAUSE A MALFUNCTION CAUSING PROPERTY DAMAGE, PERSONAL INJURY OR DEATH.

Either condition could indicate an incomplete powder burn and/or a bullet stuck in the bore. Retract the Bolt slowly and remove the fired cartridge case. Clear the Firearm and check for unburned powder grains in the Receiver or Bore, and for a Bullet stuck in the Bore. Clean out any unburned powder before resuming firing. If a Bullet is stuck in the Bore, do not attempt to remove it.
Take the Firearm to a qualified Gunsmith.

STOCK ADJUSTMENTS

  1. To adjust the Cheek Piece height, slide the Cheek Piece rearward to unlock.
    ac-18-stock-01.png
  2. Lift Cheek Piece to the elevated position.
    ac-19-stock-02.png
  3. Slide Cheek Piece forward to lock into place.
  4. Reverse action in order to return Cheek Piece to the lower position.

OPTIONAL – FOLDING/TELESCOPING STOCK

  1. To adjust the length of pull, depress both (left and right) Stock Extension Buttons and slide stock forward or back.
    ac-20-stock-03.png
  2. To fold, depress the Stock Release Latch and fold the Stock forward on the right hand side.
    ac-21-stock-04.png
  3. To return the Stock, pull to the rear until the Stock locks into place.

NOTE: Stock is held open by detent but does not lock open.

NOTE: The Firearm can be fired with the stock in the folded position with clearance for ejecting cartridges.

IMMEDIATE ACTIONS — IN CASE OF TROUBLE!

IF YOUR FIREARM STOPS FIRING: Perform the following IMMEDIATE ACTIONS…

Remember the word “SPORTS

  1. Slap up on the Magazine to ensure a good lock up in the Lower Receiver.
  2. Pull the Charging Handle all the way back and hold.
  3. Observe the ejection of the Case or Cartridge, check Chamber for any obstruction.
  4. Release the Charging Handle and let the Bolt spring forward.
  5. Tap the Charging Handle to assist the Bolt forward to ensure the Bolt is locked.
  6. Squeeze the trigger to fire.

ac-22-sports-01.png

REMEDIAL ACTIONS…

WARNING: IF YOUR FIREARM STOPS FIRING WITH A LIVE ROUND IN THE CHAMBER OF A HOT BARREL, REMOVE THE ROUND IMMEDIATELY. However, if you cannot remove it within 10 seconds, remove the Magazine and wait 15 minutes with the Firearm pointing in a safe direction (always check that the “SAFE” direction remains safe during that time). This way you and those around you won’t get hurt by the possibility of a round “cooking off”.

ac-23-remedial-01.png

KEEP YOUR FACE AWAY FROM THE EJECTION PORT WHILE CLEARING A HOT CHAMBER.

  1. If your Firearm still fails to fire after performing Immediate Action Steps 1 through 5, check again for a jammed cartridge case.
  2. If a cartridge case is in the chamber, open the receivers, remove the bolt carrier, and try to tap out the case with a cleaning rod.
    ac-24-remedial-02.png

IF FIREARM STILL FAILS TO FIRE CHECK THE TROUBLESHOOTING SECTION IN THIS MANUAL OR TAKE THE FIREARM TO A QUALIFIED GUNSMITH.

BULLET STUCK IN THE BORE…

WARNING: IF AN AUDIBLE “POP” OR REDUCED RECOIL IS EXPERIENCED DURING FIRING, IMMEDIATELY CEASE FIRE: Then,

  1. Remove the Magazine.
    ac-25-bullet-01.png
  2. Lock the Bolt to the rear.
    ac-26-bullet-02.png
  3. Place the Selector Lever on SAFE.
    ac-27-bullet-03.png
  4. Visually inspect and/or insert a Cleaning Rod into the Bore to ensure there is not a Bullet stuck in the Bore.
    ac-28-bullet-04.png

DO NOT APPLY THE “IMMEDIATE ACTIONS” DESCRIBED ABOVE. IF A BULLET IS STUCK IN THE BARREL OF THE FIREARM, DO NOT TRY TO REMOVE IT. TAKE THE FIREARM TO A QUALIFIED GUNSMITH.

BACK UP SIGHTS

The Front Sight Post is threaded - allowing it to be moved up or down for Elevation Adjustments when “Zeroing” the Rear Sight (see “Zeroing Your Sights”). Once the Rear Sight is Zeroed, the Front Sight Post should not be moved.

ac-29-sights-01.png

REAR BACK UP SIGHT

The Rear Back Up Sight features two apertures and when not used can be folded down flat. To return to the up position press either the side tabs.

ac-30-sights-02.pngac-31-sights-03.png

NORMAL RANGE APERTURE:

The smaller Aperture is the default setting and is used for most firing situations, optimized for 100-300 meters.

SHORT RANGE APERTURE:

Rotate the Normal Range Aperture forward and down to reveal the Short Range Aperture. This aperture  is used for ranges of 0 - 100 meters, allowing a larger field of view.

When not in use the Front and Rear Sights can be folded down flat. To return elevate sights press down either the side tabs or down on the forward portion of either sight to engage the spring loaded release. To remove the sights, loosen and remove the Locking Bolt and guide the sights forward off the end of the MIL-STD-1913 Picatinny Top Rail.

ZEROING YOUR SIGHTS…

Follow the steps below to establish a Zero at 25 meters. Your MBUS Type Rifle Sights will then be set with a 300-meter battlesight zero. With this procedure, only the Front Sight Post and Rear Sight Windage Knob are adjusted so that you can hit your Point of Aim at 300 meters.

25 METER ZEROING PROCEDURES…

  1. Place an appropriate 25 Meter Paper Sighting Target 25 meters downrange and follow the steps below to establish a “battlesight” zero. Do not move the Front Sight Post at this time. It was set at the factory and should be very close to “Zero”.
    (Bushmaster Sighting-In Targets, Part# QP-015K - see Bushmaster Catalog or Website)
  2. The smaller (unmarked) Rear Sight Aperture should be in the UP position. Center the Rear Sight by turning the Windage Knob left or right. This creates what is called “Mechanical Zero Windage”.
  3. Check that your field of fire is clear, and that it is safe to shoot. Carefully aim and fire a group of three shots at the center of the target bullseye.
  4. Inspect your target - if your shot group is not in the center of the bullseye, the squares on the target sheet will help you calculate the required “clicks” necessary to move your next shot group toward the bullseye.
    (Remember! - any changes in elevation are to be made by moving the front sight post)
  5. If you need to raise your next shot group to get closer to the bullseye, rotate the Front Sight Post clockwise one click. A Front Sight Adjustment Tool (Part# RAY-005 - see Bushmaster Catalog or Website) is recommended for this but not necessary – the sight can be adjusted with the tip of a Bullet as shown at right. One click will move the bullet strike point one vertical square on the target sheet.
    ac-32-zeroing-01.png
    Elevation Adjustment Table
    1. Sight Radius: 14.1 in.
    2. Bullet Strike Adjustment
      Impact Distance
      0.485 in./click 25m
      1.939in./ click 100m
      5.817 in./click 300m
  6. If you need to lower your next shot group, rotate the Front Sight Post counterclockwise. (One click - as before – equals one square.) Changes in Windage are made with the Windage Knob on the Rear Sight. To move the shot group to the left, turn the Windage Knob counterclockwise. To move the shot group to the right, turn the Windage Knob clockwise
    ac-33-zeroing-02.png
    Windage Adjustment Table
    1. Sight Radius: 14.1 in.
    2. Bullet Strike Adjustments
      Impact Distance
      .323 in./click 25m
      1.293 in./click 100m
      3.878 in./click 300m
  7. Carefully aim and fire another group at the center of the target bullseye. Repeat Steps 5 and 6 as required to get your shot groups into the bullseye.
  8. Once your shot group is on target, your Sights are zeroed, or “calibrated”.

DISASSEMBLING YOUR FIREARM…

  1. CLEAR YOUR FIREARM! (as described above). Disconnect the Sling for convenience.
  2. Push the Rear Takedown Pin (a Bullet Tip can help) as far as it will go. Pivot Upper Receiver from Lower Receiver.
    ac-34-disassembling-01.png
  3. Push in Pivot Pin (a Bullet Tip can help).
    ac-35-disassembling-02.png
  4. Separate Upper and Lower Receivers.
    ac-36-disassembling-03.png
  5. Push the Charging Handle fully forward to disconnect the Actuator from the Bolt Carrier. Remove Bolt Carrier to the rear.
    ac-37-disassembling-04.png
    NOTE: Pivot Pin in the Lower Receiver and Takedown Pin in the Upper Receiver are “captivated” - meaning that they are held in by their Detents and Springs so they cannot fall out and get lost.
  6. Remove the Action Spring Assembly from the Bolt Carrier by pressing inward (toward front of the Bolt) and twisting counter-clockwise until the slots on the carrier are in-line with the prongs on the front of the Action Spring Assembly Guide and then remove the Action Spring Assembly.
    ac-38-disassembling-05.png
  7. Remove Firing Pin Retaining Pin. A Bullet Tip can help push it out of the Bolt Carrier.
    ac-39-disassembling-06.png
  8. Remove Firing Pin and Firing Pin Spring out of rear of Bolt Carrier.
    ac-40-disassembling-07.png
  9. Remove Cam Pin by turning Bolt Carrier on the side and tapping opposite side of Bolt Carrier. Cam Pin should fall out.
    ac-41-disassembling-08.png
  10. Remove Bolt Assembly from Bolt Carrier by pulling straight out.
    ac-42-disassembling-09.png

DISASSEMBLE USING STEPS 11 AND 12 ONLY WHEN DIRTY OR DAMAGED

  1. Remove Extractor Pin by pushing out with a punch or the tip of a Bullet.
    ac-43-disassembling-10.png
  2. Remove Extractor with Spring.
    ac-44-disassembling-11.png
    NOTE: Press rear of Extractor to check Spring function.
    CAUTION: Extractor Spring may pop out and get lost!

REMOVING THE BARREL ASSEMBLY

  1. Pull Charging Handle and lock to the rear.
    ac-45-disassembling-12.png
  2. Remove Hand Guard by pushing the Hand Guard Retaining Pin through as far as it will go and slide the Hand Guard forward.
    ac-46-disassembling-13.png
  3. Lower the Barrel Locking Lever and depress the Barrel Plunger.
    ac-47-disassembling-14.png
  4. With the Barrel Plunger depressed, turn the Barrel Locking Lever counter-clockwise until it stops.
    ac-48-disassembling-15.png
  5. Pull the Barrel Assembly forward until it releases from the Trunnion.
    ac-49-disassembling-16.png

DISASSEMBLING THE GAS PISTON SYSTEM

  1. Depress Regulator Plunger and rotate until it is facing toward the barrel.
    ac-50-disassembling-17.png
  2. Pull Gas Regulator straight out to remove.
    ac-51-disassembling-18.png
  3. Remove Piston Rod and Piston Spring through the front of the Gas Block.
    ac-52-disassembling-19.png
    NOTE: The Gas Piston System can be disassembled with the Barrel attached or removed from the Upper Receiver.

ac-53-stop-sign.pngBUSHMASTER DOES NOT RECOMMEND ANY FURTHER DISASSEMBLY. ANY FURTHER DISASSEMBLY MUST BE PERFORMED BY A QUALIFIED GUNSMITH.

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