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.

The MRP is the first monolithic upper receiver.  The upper receiver is machined from a single 7075 T6 aircraft aluminum forging.  There are four solid Mil-Std 1913 rails and permit complete zero retention for optics or any other accessory placed on the rails.  The upper receiver is equipped with a forward assist, fired cartridge case deflector as well as an ejection port dust cover.  All rails are numbered for easy replacement of optics to insure they are placed back in the same position from which they were removed.  Removable sling swivel mounts are placed on the end of the MRP at the 3, 6 and 12 o’clock positions.  Additionally, mounting points are located on the right and left side at the rear of the handguard area by the ejection port.  This permits any type of sling or desired location for the operator’s discretion.

The innovation does not stop with the development of the first one piece monolithic rail platform.  The barrel, held in by two bolts, is removable by the user.  When the bolts are removed the barrel/gas tube assembly is pulled straight out of the receiver.  This enables the 5.56mm caliber weapon to be configured for whatever mission it will be used.  If a close quarter combat environment is the mission, a 10.5 inch barrel may be used.  If the mission is urban or normal combat ranges, a 14.5 or 16 inch barrel may be used.  If longer range is required, an 18 or 20 inch barrel may be used.  It should be noted the 16 inch 5.56mm barrel uses a mid-length gas system and all others use a standard carbine gas system.  All is accomplished at the user level; no armorer is needed to change out the barrels.  The barrels are manufactured from machine gun barrel steel and button cut rifling.  They are cut with the Mil-Spec 1 turn in 7 inch twist allowing up to 80 grain projectiles to be stabilized.  The barrels have chrome plated bore and chambers and are equipped with an A2-style compensator.  With Lewis Machine & Tool being a U.S. government contractor for many different parts, they are familiar with what Mil-Spec means and what it takes to achieve it.  All barrels manufactured by Lewis Machine & Tool are proof tested with a 70,000 psi proof cartridge and then magnetic particle inspected to insure the barrels are free of stress fractures.  When the barrel is installed in the MRP, the barrel is completely free floating.  This increases accuracy as well as the air holes in the MRP circulate air to aid in cooling.  The removable barrels also enable another innovation: the MRP is a multi-caliber weapon as different caliber barrels can be used.  Complete changing of the barrel is accomplished in less than 5 minutes.

The MRP provided for this evaluation came with many enhancements that are all Karl Lewis.  Starting with the sights, the rifle was provided with the LMT BUIS (Back Up Iron Sight).  This is a fully adjustable rear sight that has been provided to the U.S. Navy and SOCCOM for the MK18 CQB 10.3 inch carbines.  The sight is identical to that of the standard M16A2 or M4.  The front sight is removable and held on by a nut.  It has the traditional triangular shape and square front sight post.  Of course, being a Mil-Std 1913 rail, any BUIS can be mounted.

The charging handle has an improved latch that is easier for one to grasp as it is made wider so it is easier to actuate.

The bolt and carrier are also a significant departure from the norm.  When Lewis looked at the new design, he looked at the specific operating dynamics of the carbine and how different it is from the rifle.  Given the different dynamics, Lewis designed the bolt and carrier to function with that in mind.  To begin with, the bolt carrier has had several modifications.  Due to the dynamics of the carbine, the bolt unlocks at a faster rate on a carbine length gas system than a full length rifle.  Owing to this quicker action, there is still residual pressure in the cartridge case and it is still somewhat expanded when the rifle starts to extract making the extractor and extractor spring work that much harder to extract that cartridge case.  It also causes extractor springs to wear quicker than that of the rifle.  SOCOM has added rubber O-rings to increase the extractor force to cope with the wear issue.  The standard GI M4 has a new and improved extractor spring (copper in color) that is designed specifically for the carbine to increase extractor force.  Lewis also redesigned the geometry of the cam track by increasing the dwell time upon unlocking and thus permitting additional time for the residual pressure to drop allowing much easier cartridge extraction.  He also added an additional gas relief port to get rid of unneeded gas.

All LMT lower receiver assemblies come with the LMT produced ambidextrous selector lever. These are made in both semi-auto only and selective fire models.

The bolt was also redesigned with durability on mind using proprietary material that is significantly stronger than standard bolt material.  Due to its hardness it is more expensive to procure and more expensive to machine than standard bolt steel.  The geometry of the locking lugs has been modified as well.  There are stress relief cuts that allow more flexing of the lugs to prevent breakage.  The extractor has been redesigned as well.  The improved “lobster tail” extractor uses two extractor springs instead of one that significantly enhances the reliability of the extractor in adverse conditions.  The extractor claw is considerably more aggressive and stronger as well.  Like the barrels and as per Mil-Spec, all LMT bolts are proof tested and them magnetic particle inspected.

The lower receiver has many enhancements as well.  The stock is the LMT SOPMOD stock and is the stock assembly purchased by USSOCOM and the U.S. Navy for the M4A1 carbines and the MK18 CQB weapons.  The stock is triangular in shape and very smooth.  There are two removable sling mounting points on the stock as well as a cut-out for a standard GI silent sling.  There are two battery compartments that are water resistant tubes placed inside of the stock and there is a removable rubber butt plate as well.  The receiver extension is also designed by LMT and has six positions as opposed to the standard M4 which has 4 positions.  The provided pistol grip is the Ergo Grip that is extremely comfortable and with the finger grooves is comfortable and makes the rifle stable in the shooting hand in adverse conditions.  Also provided on the lower receiver is the Ergo Grip Gapper.  This little spacer covers the gap in-between the front of the pistol grip and the trigger guard.  LMT’s proprietary ambidextrous selector lever is also provided.  This is not just good for left handed shooters but can be just as useful to right handed shooters as well given the tactical situation.  Tangodown rail covers were provided on the rails.

The rifle was outfitted with the new EOTech XPS2-2 two dot reticle holographic sight.  Extremely compact, this sight uses a single 123 battery and has a battery life is 500 to 600 hours.  This sight only requires 2.75 inches of rail space.  Along with the sight is the EOTech Generation II 3X magnifier.  This comes with a Samson Quickflip tilting mount attached to an A.R.M.S. throw lever mount.  When disengaged, the magnifier sits to the right side of the rifle: when engaged for long range shooting it flips back.

Also provided was the LMT Rebar cutter. Due to troops in the Middle East blasting walls and rebar getting n their way of going through, Lewis designed this rebar cutter that mounts over the flash suppressor. The cutter is placed over the rebar, a round is fired and it cuts through the rebar.

Also attached to the rifle was the Insight Tech M3X tactical light with pressure pad activation that was mounted in a Tangodown vertical foregrip.  By just removing a spacer, the pressure pad sits in the grip.  The grip also is hollow allowing for additional storage.

The magazines chosen for the rifle are the Magpul PMag, one of the finest magazines available anywhere in the world for the Black Rifle.  This magazine is a significant reliability enhancement to any member of this family of weapons.  The constant curve design allows the shot column to sit in its natural shape and increase feed reliability.

The ammunition for this test was provided by Silver State Armory (SSA).  SSA is known for manufacturing some of the highest quality duty and match ammunition in the industry at competitive pricing.  Silver State Armory just moved to a state-of-the-art facility in Packwood, Washington where they have a 100 meter underground range and the facility meets United States Department of Defense requirements to manufacture military contract ammunition.  They manufacture their own brass.  All SSA ammunition is loaded with custom blends of powder geared towards the specific loading.  They offer several loadings in 5.56mm, 7.62mm NATO, 6.8SPC and .499 LWRC.  They are also one of the only ammunition manufacturers in the United States to manufacture armor piercing rifle ammunition in 5.56mm, 7.62mm NATO and 6.8SPC.

More than 300 rounds of SSA 5.56mm 55gr FMJ rounds were fired through the MRP for function testing and no malfunctions were encountered.  There were 200 rounds of SSA 5.56mm 77 grain OTM cartridges fired as well.  Groups at 100 yards kept around 1.75 inch groups consistently with the FMJ rounds.  All in all, this barrel has had more than 500 rounds through it and as it has broken in the groups had tightened up.  First groups fired with the SSA 5.56mm 77 grain OTM were consistent at 1.75 inches.  The last groups fired with this ammunition were printing consistently at 1 MOA.