Rifles > Semi-Auto

The Bushmaster ACR

Bushmaster’s ACR is a transformative firearm.

The Bushmaster ACR is a firearm both propelled and burdened by its legacy as the Magpul Masada. First unveiled at the 2007 SHOT Show in Orlando, Fla., the gun created quite a stir among the semi-automatic rifle aficionados in attendance. The Masada promised to deliver first-rate ergonomics and versatility in the form of its quick-change barrel capability and adaptability to alternate calibers.

Magpul had something good but it didn’t have the resources to produce the gun, so in 2008 it sold the design to Bushmaster, which re-named the firearm Adaptive Combat Rifle (ACR). Bringing a gun like the Masada to market would be a tough job, but Bushmaster and Remington, both members of the Freedom Group family of firearm companies, shared their resources and unique expertise to make the promise of the Masada a reality. Magpul may have sold its rights to the gun, but it remained heavily involved in the development of the ACR.

Bushmaster and Remington will both sell ACRs. Bushmaster will handle civilian and state and local law enforcement sales, while Remington will handle potential ACR sales to federal law enforcement and the military. Bushmaster will offer two models, the Basic and the Enhanced, with the only significant differences being the stock and the fore-end. The Basic will have a fixed stock and polymer fore-end and the Enhanced will have a folding stock and a quad-rail aluminum fore-end. I received an Enhanced ACR for examination and testing.

A Better Mousetrap
The ACR dispenses with the direct gas-impingement operating system of the M16 in favor of an AR-180-style indirect gas-impingement system. Gas tapped from a port in the barrel travels through the gas block and impinges on a tappet rod above the barrel. Energy from the expanding propellant gases drives the tappet rod back. The tappet rod in turn strikes the face of the bolt carrier to unlock the bolt.

The ACR has a short-stroke rotary bolt with eight equally spaced locking lugs that engage an extension on the breech end of the barrel. Seven of the lugs have the same height, width and depth, while a smaller eighth lug is part of the extractor. A plunger ejector can be found on the recessed bolt face. There are no gas rings on the bolt body, as it’s not a direct-gas gun, so it doesn’t need them. A coil spring wrapped around the steel firing pin reduces the chances of a slam fire. Rotation of the bolt is controlled by a cam pin that travels in a kidney shaped cut-out in the left side of the carrier.

The bolt carrier slides on a single action rod that controls the compression of the recoil spring. A white polymer buffer is fixed to the tail of the action rod. U-shaped steel guide rails anchored to the aluminum upper receiver by machine screws control the vertical and horizontal movement of the bolt carrier as it travels back and forth during the firing cycle.

The advantages of the ACR’s operating system are: It has no need for a separate buffer extension, so it is compatible with a folding stock; the travel of the blocky bolt carrier is less likely to be impeded by dirt or accumulated fouling in the upper receiver; and much less fouling and heat is vented into the bolt and action mechanism during firing. Most of the fouling is trapped in the gas block. Thankfully, the two-position gas regulator, along with the tappet rod and action spring, can be removed for cleaning. The two-position regulator can be rotated in either a clockwise or counter-clockwise direction. The “S” setting is for firing with an attached suppressor and “U” setting is for normal unsuppressed operation.

Quick-Change Barrel
The standard barrel length for both the Basic and Enhanced models is 16 1/2 inches. Remington representatives told me that their internal testing determined the barrel’s ideal thickness and stepped profile for maximum longevity. The 10 1/2- and 14 1/2-inch-barreled guns will be available to law enforcement customers and Bushmaster will offer 18-inch-heavy barreled guns as Designated Marksman-style rifles. Most of the shooters I know who are eager to buy an ACR will likely want to shoot it with 75- and 77-grain loads, so the 1:9-inch rifling twist of our test gun seems to be an odd choice. Bushmaster told me that 1:9 inches was the most popular choice among its distributors, but I was assured that guns with 1:7-inch barrels will be available, and separate 1:7-inch barrels will be available through a spare barrel program. Also 6.8x43 mm barrels with Spec. II chambers will be introduced in the same lengths. All ACR barrels in both chamberings are cold-hammer forged with six grooves in a right-hand twist.

A barrel nut with interrupted threads locks the barrel assembly into a steel trunnion fixed to the upper receiver by way of two roll pins and two machine screws. A hinged barrel wrench attached to the barrel nut makes it easy to dismount the barrel for cleaning or swapping calibers. It should be noted that a caliber change will also require replacing the bolt and magazine.

To change the barrel, simply lock the bolt to the rear. Knock out the captured ferule pin at the bottom rear of the aluminum fore-end. Pull the U-shaped fore-end forward and off of the gun. Pull down on the hinged barrel wrench and rotate the barrel wrench/barrel nut lever one-quarter turn to the left. Then unseat the barrel nut from the trunnion by pulling forward on the barrel wrench. The barrel assembly and the attached gas system assembly can then be removed.


The upper receiver is a U-shaped, one-piece assembly of extruded aluminum that extends from the wrist of the stock to the gas block. An integral M1913 Picatinny rail runs the full length of its roof. A shell deflector is mounted behind its large ejection port. The upper receiver also serves as a housing for the reversible charging handle, the bolt, and the steel trunnion that provides a common joint for the ACR’s upper and lower receivers and its detachable barrel.

Magpul specializes in polymer accessories for the AR-15/M16 platform, and the ACR’s polymer lower receiver is a legacy of its Magpul origins. The lower receiver consists of an integral pistol grip, trigger well and magazine well. All of the fire and function controls including the trigger, ambidextrous safety lever, ambidextrous magazine release and bolt stop buttons are contained in the ACR’s lower receiver. It also serves as a mounting point for the buttstock, which is held in place by both a tongue-and-groove joint and a captured steel ferule pin at the rear of the assembly. Like the M16, the upper and lower receivers are hinged on a captured pivot pin in front of the magazine well. Unlike the M16, the rear take-down pin is housed in the upper rather than the lower receiver.

The skeletonized polymer stock of the ACR Basic is fixed with a 12-inch length of pull that can be extended with compatible inserts from Magpul. In contrast, the stock of the Enhanced is adjustable in every way imaginable. The comb can be raised a 1/2 inch and the user can choose one of seven settings for length of pull, ranging from 11 to 14 inches in 1/2-inch increments. A push-button release on the left side of the stock near the wrist allows the stock to fold over the right side of the receiver. When folded, it is held in position by tension but doesn’t really lock. This is something of a compromise that allows it to lock back in its extended firing position without pushing any buttons. When folded, the stock does not block the ejection port, but shooters may find that it impairs access to some of the left-handed controls on the right side of the receiver including the safety lever and magazine release button. Battery storage compartments are included in the stock and pistol grip. They are compatible with most of the Magpul MIAD Grip Core inserts.

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26 Responses to The Bushmaster ACR

Ranger144 wrote:
August 16, 2013

Bigpimin117, the .223 and 5.56 are not the same round contrary to popular belief. The 5.56 produces a higher chamber pressure and the should angle on the 5.56 is a bit steeper. The rounds are very similar but not exactly the same and therefore a gun/barrel that is only rated for .223 ammo should not fire 5.56 ammo. If you have an m4 check the barrel. It will be stamped either '.223' or '.223/5.56'.

Cory wrote:
June 12, 2013

I have owned a Bushmaster ACR for about 3 months now i have close to 2000 rounds threw mine and i have not had one failure i use the rifle as i would my duty rifle i train with my ACR in CQB and in almost every other environment you could expect in a real world situation and it has never failed me. People complain about the weight i do not see a weight issue if your a real world operator you can expect to be carrying a 8 pound weapon with the right optics and weapon light you can keep the weapon pretty light as far as weight goes if you do it right. As for some screws coming loose thats why they make lock tight nothing is perfect even if you do spend 2800 on a rifle.

bigpimpin117 wrote:
May 10, 2013

.223 and 5.56 is the same round how can you have hang ups with the same round

john wrote:
December 31, 2012

I purchased an enhanced ACR 2 weeks ago. I fire mine with an AWC systems suppressor. I have fired around 300 rounds through it so far with no issues. Its a little heavy but its made well. The trigger is the same as a standard army m-4. It does much better with the suppressor due to the piston than my ar-15. Overall very pleased. As for FN...... I have fired many of their AR series rifles and would never pay money for one.

Warren C Knight wrote:
September 27, 2012

Great article! Very concise and detailed evaluation with relevant info only. I've been racking my brain for weeks weighing the pro's and con's and cost/benefits in an attempt to come to a regret-free decision whether or not to buy this beautiful gun. One of the biggest factors in the pro category is that I also am a left handed shooter. Having read this thorough article authored by a fellow lefty, I feel almost like I evaluated the gun myself. All my concerns are addressed here, as well as the features that interest me. Great work!

Bill wrote:
August 12, 2012

Just bought one three days ago. I am surprised that after firing 500 rounds through it the screws on the upper are flying off. Bushmaster is sending replacements but really, good luck with that as a military weapon. I could not recommend the ACR. Those screws are either a shoddy design, they should not be popping off.

Zac wrote:
April 04, 2012

Amazing weapon fires great a little expensive but definently worth it. First day shot about close to thousand rounds through no stoppages at all barley any recoil easy to zero shoots like a AR/M4 with the durability of a AK truely an epic must have

Ernest wrote:
March 06, 2012

I've had mine for awhile. The first thing I did was change the trigger, 8.5-9# was too much. Haven't shot it a lot. Looking for suggestions on an accurate load.

Someone wrote:
March 06, 2012

people just Complain about the weight. Dealt with it people!!! the guns just way to much for me to buy but. i would love to own one.

eric wrote:
February 13, 2012

I just looked at one of these rifles yesterday at a gander mountain store and I wasn't as impressed as I thought I would be, especially for the $2050 price. I figured for that price the rifle would at least come with would decent trigger. It felt like the same old factory trigger that came in my ar15. i also noticed that the upper and lower halves of the rifle bad a little wobble to them. And like others said, the gun is definitely way too heavy. I think money would be much better spent on a Robinson armament xcr rifle.

Chad wrote:
December 21, 2011

looking for some more up-to-date reviews i know the gun has been out for awhile now and im looking at buying one myself.. just curious what the final verdict is on this gun..

Robert wrote:
December 15, 2011

Any updates to how your guys' ACRs are treating you?

Rick wrote:
November 29, 2011

I've noticed problems firing the .223 also...the bolt won't lock back after firing the last round of a magazine. No problems firing the 62 grain 5.56 though.

Cary wrote:
September 20, 2011

Just ordered my basic ACR after some debate. Articles like this helped me make my final choice. Am ex-CANSOF and am looking forward to some great shooting opportunities with what sounds like a very well thought out rifle.

gewamser wrote:
August 06, 2011

Great rifle! But at 8.3 lbs TOO HEAVY!

Dean J Vandall wrote:
July 17, 2011

I can't say enough about the ACR. Having waited so long for this rifle to hit the market, I can say without a doubt it was worth the wait. Magpul designers, using the AR-180's bolt and piston basic design was a smart move (one that had the army made back in the day, would have set a new standard for rifles (and I can only think of the lack of reliability issues coming from SE Asia)I have the enhanced model, but puchased the original forend because I am a huge fan of the original lines of the Masada. I can't say I have found the stock when folded in the way of the controls at all really. I'm a left handed rifle, and right handed pistol shooter, but practice strong and weak side often, and this rifle is a blessing in that regards. The only thing I can say is that this rifle, when fitted with a solid tac-light, fore grip, etc, can feel a little heavy. The added weight works well though for absorbing an already mild recoil. When the 6.8SPC conversion kits hit the market, I think this attribute will be even more appreciated. I have fired both light 50grn up to 72grn projectiles, using the standard 25 meter zero we use in the army. I have noticed zero impact on accuracy. With my EOTech I have used the same range of rounds to dispatch clay pigons at 100 meters with ease. Some have expressed disapointment with Magpul for selling the design to Bushmaster and Remington, but I applaud them. It's a smart move to take a brilliant idea and make it a reality through outsourcing. Good thing is that the polymer parts are well marked with Magpuls micro logo for the stippling and if you fold the buttstock, you'll see the logo inside the receiver as well. When compaired with other rifles on the market, this is one of the only rifles that affords the operator a truly tooless barrle change. You could change barrels and calibers in under 60 seconds with a little practice. So my hats off to Magpul for the disign, and Bushmaster/ Remington for making it a reality for us all.

Caleb Roy wrote:
May 18, 2011

I love the ACR soooooooooooooooooooo much!! !!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!

Ryan wrote:
April 02, 2011

Would just like to clarify/add, Bushmaster was bought out by remington/cerberus corporation. The bushmaster name lies under remington and will be servicing both public and federal sales.

Vincent wrote:
January 11, 2011

Recently purchased the enhanced ACR (1/7/2011). I was set on a Ruger SR556, looked at Sig, and REC7, and gave up on HK. After handling the ACR the choice was easy. Also looked at POF, and S&W. Don't regret the money spent. Very well made and versatile weapon. It is a little heavy, and for the money they could have dispensed with the rifle case and provided a smaller tactical case and some spare mags. The identical case can be purchased at K-Mart for $39 without the bushmaster name. Still to early to tell how well the ACR wears, but thus far don't see any problems (1,000 rds). Once magpul sights zeroed accuracy is good. At first the polymer construct of the magpul sights turned me off, however they are pretty robust. Only thing I liked about the Ruger was the troy sights. The stock sucked, as did balance. Did like the sight picture better than the magpuls, however the weapon looks better on the web then in reality. Can't wait to buy another barrel of different caliber. If you are used to an AR bolt carrier, this is another animal. My wife who knows nothing of firearms could take down, clean. In my opinion this is a rifle to pass on to the next generation. The price is a little prohibitive, however doubt anyone will have buyer remorse post purchase.

Michael P wrote:
December 02, 2010

I bought an ACR basic model in Flat dark Earth. I like it very much. I was not happy the recall, but that is old news. They gave me 2 mags for the trouble. I never had any slam fire or muliple rounds firing, I also only use 5.56. The 1in9 twist does not bother me either because I use 55 grain bullets. When the 6.8 comes out i plan to pick it up. That was my main reason for picking the ACR.

AJ wrote:
November 25, 2010

Nice article, I've been following this rifle from its begining. I was hoping for a 6.5 grendel one as well but i see that may not happen at all. So to me this rifle is loosing its appeal as time goes on.

Justin wrote:
October 26, 2010

I just received my ACR. before taking it to the range I thoroughly cleaned it and lightly oiled it like you would an AR. I put 200 rounds through it and it worked flawlessly. The only grip that I have with it is that the bolt's 'coating' had already begun to chip off around the teeth. I just hope the same thing isn't happening in the barrel. Also I had to send my ACR back to Bushmaster do to their slamfiring recall. guess all the testing wasnt enough...

Dale wrote:
September 20, 2010

purchased an ACR. I like the rifle. However, I did find that recoil was more than my LMT CQB MRP and Noveske N4. I plan to install a PWS FSC556 and see if it reduces muzzle flip. I am still happy with my purchase. I like the easy change barrel and the versatility to be able to change calibers. The LMT gives me that ability as well but requires the use of a torque wrench. If the PWS FSC556 works well, the ACR will become my go to rifle.

Tobin Roos wrote:
September 09, 2010

I bought an ACR Enhanced. It fires 5.56 ammo just fine, but it slam fires .223 rounds on a regular basis. Google it, some one shot off their big toe during a slam fire.

Boss man wrote:
September 05, 2010

When talking about the "Remington's proprietary coating", the article says twice that it "dispenses with the need for any additional lubrication", i believe this is a typo and meant to say {without}. By the way I recently purchased an ACR and I love it. Great article and very informative.

Dan Boldo wrote:
September 01, 2010

Well written article. I liked the attention to detail and clear style. As a left handed shooter, I especially appreciated the extra information that most other folks ignore. It's a very good review of what appears to be a very good rifle. Thank you and well done, Cheers, Dan