Bushmaster ACR Adaptive Combat Weapon System

The sample rifle was extremely accurate with Silver State Armory 69grain OTM ammunition. Groups hovered between 1” to 1.5” @ 100 yards.

At the 2007 SHOT Show, Magpul introduced their Masada Adaptive Combat Weapon System.  There was quite a buzz around the booth from both the introduction of the Masada as well as their revolutionary new PMag polymer magazine.  The Masada is, of the entire current available piston operated 5.56mm weapon systems, the most advanced and conceptionaly new weapon system out.  Unlike the POF, Heckler & Koch and LWRC models, the Masada is not based off of an existing M4 weapons platform.  Like the Heckler & Koch XM8/G36 weapon systems and the British SA80 weapon systems, the Masada uses technology borrowed from the Eugene Stoner designed AR-18/AR-180 weapon systems of the early 1960s.  The Masada however, takes it to the next level.

The Masada name comes from the battle of Masada where the Roman X Legion laid siege to the Jews in 72 AD.  The fortress stood on top of a plateau and had a secure source of fresh water.  Due to this, the Romans were forced to build a ramp to permit their formations to attack the fortress without breaking ranks.  With the ramp being nearly complete, the Jewish defenders decided to end their existence rather than come under Roman rule.  The citizens of Masada left their food out in plain view so the Romans could see they were in no danger of starving and through this act of defiance, the citizens of Masada decided they would kill themselves rather than have their women and children raped and enslaved by the Romans.  The entire town perished by their own hand.  They controlled their own destiny.  Magpul found the story of Masada a bold example of defiance.  Most weapon systems bear the name of their designer; the Masada name is more of a symbol of defiance.

The Masada is the first weapon system to be developed by Magpul.  Magpul had thought of a firearm design for several years; however it was not until 2006 when pen went to paper.  Magpul’s Mike Mayberry headed the Masada design team and was designed in only 4 months time.  Like many other firms, their initial goal was to take the current successful M16/M4 weapon systems and incorporate those desirable traits into their weapon system.  Due to the excellent human engineering characteristics of the M16 weapons platform, this is a good starting point and it would offer potential users an easier transition.  During the developmental stages, many weapon systems were looked at.  Upon examination of different systems, Magpul was able to extract what they felt were the benefits of each design and would incorporate those into their final design.  Magpul was, however, able to keep some parts commonality with AR-15/M16 components.  These parts are the barrel and barrel extension, trigger, disconnector, hammer assembly, hammer/trigger pins, trigger spring, front sight assembly, extractor pin/spring/plunger, ejector/spring and retaining pin.

Magpul found that to retrofit the standard M16/M4 weapon system with their improvements would be quite difficult and costly.  In March of 2006 the decision was made to abandon the retrofit design and start from a clean sheet of paper and in the fall of 2006 the project commenced from scratch.  As previously stated, they would model the mechanics of the operating system of the AR-18/AR-180 though they had to make many modifications from that design.  The AR-18/AR-180 was not a combat proven design by any means.  The ArmaLite rifles were never manufactured in quantity for military sales – only for commercial sales.  The first military production of this system was the British SA80 which was, and is still, a disaster.  The H&K XM8 was never fielded and the G36 has seen limited use.

The author putting the Bushmaster ACR through its paces. Notice the AimPoint Com4 reflex sight and the Magpul PMag.

The Masada was covered in extensive detail in a previous SADJ exclusive (Vol. 1, No. 1, 2009).  However, that was with the Masada prototype.  Like ArmaLite in the 1950s, Magpul saw itself as a design firm and not a firearms manufacturer; so they would team up with a company that was geared towards manufacturing: Bushmaster firearms.  In January 2008, Bushmaster entered into a licensing agreement with Magpul where they would take on manufacturing and all further development of the ACR.  However, Magpul remained heavily involved with the development.  Bushmaster initially announced product release in second quarter 2008 but for various reasons it would not actually be released for production until 2009 – but not in major numbers until 2010.  Also the ACR was shown at Industry Day as a potential candidate to replace the M4 carbine as the next U.S. service rifle.  That has yet to be seen and it will likely compete in the trials in the summer of 2011.

Bushmaster realized early on that as received the Masada was not designed for mass production and several changes needed to be made.  The barrel assembly changes incorporated a different locking mechanism, barrel profile, and the ability to access the operating system from the front for ease of maintenance.  They also increased the reliability, durability, and maintainability of the system through design changes, coatings, and alternate materials.  Changes were also made in the brass deflector, hand guards, and lower (alternate material) to comply with military specifications.

The ACR is a truly modular weapon.  Everything including the stock, trigger group, barrel, bolt and handguard can be replaced to meet any requirement a small arm could have.  Starting in the rear of the rifle, the stock assembly is removed from the trigger group by pulling out on a captive pin and lifting it out of the receiver.  The stock strongly resembles the Magpul UBR stock.  The length has 7 adjustable settings and the cheek piece can be raised.  Additionally the stock can fold to the right side.  With the stock folded the weapon can still be fired.  The ejection port is clear and there is enough play in the stock in the closed position where a left handed shooter can manipulate the ambidextrous selector.  Additionally, the Magpul PRS precision stock has been adapted to work on the ACR lower receiver.

The lower receiver is manufactured from a super strong polymer.  It contains the pistol grip, fire control group and magazine well.  The pistol grip is based on the Magpul MIAD which has the stowaway core that takes various inserts.  The one provided with the T&E rifle accepted two of the CR123 batteries.  The trigger guard has the familiar Magpul enhanced trigger guard shape and the checkering on the pistol grip is the Magpul symbol.  The selector lever is ambidextrous and very easy to manipulate as is the ambidextrous magazine catch.  The bolt catch is ambidextrous and is located in front of the bottom of the trigger guard.  When the magazine is empty, the follower lifts the arm locking the bolt to the rear.  To close the bolt one only has to push down on either side of the lever.  The front of the magazine well has a gripping area identical to that of the pistol grip, the Magpul symbol.

The upper receiver is the serialized component.  The upper is manufactured from extruded aluminum and is marked for caliber as multi-caliber.  The upper was designed as a piston gun.  Rails inside of the receiver keep the bolt in proper alignment in the receiver.  The top rail is a continuous Mil-Std 1913 rail providing zero retention of optics.  Provided behind the ejection port cover is a fired cartridge case deflector.  To aid in the ambidexterity, the fired cartridge case ejects at a constant 1 o’clock direction insuring a left handed shooter would not be struck with a hot cartridge case.  The charging handle may be placed on the right or left side as the receiver is cut to accept it either way.

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