Forget about AK, Bushmaster ACR is the assault rifle of the future soldier

PANAGYURISHTE, (BM) – The semi-automatic rifle, which will be discussed in this review, was born as a result of Magpul’s persistent attempts to improve the main weapon of the American infantryman – the M4 carbine. Whether these attempts were successful or not, we tried to figure it out on our own.

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Any weapon becomes obsolete sooner or later. Aging is, however, relative; in some places they still fight with rifles and machine guns more than 100 years ago, and in other countries even well-proven weapon designs and schemes are constantly subject to improvements and revisions – in search of the ideal small arms for their soldiers

The Bushmaster ACR rifle has a complicated history, and its path to the civilian market for hunting rifles was tortuous and thorny. Initially, ACR saw the light of day as Magpul Masada – a modular weapon with the ability to quickly change barrels and calibers. However, Magpul did not have the necessary capacity for a full production cycle of weapons and therefore sold the rights to produce and further improve the Bushmaster rifle. So Magpul Masada became the Bushmaster ACR.

But her adventures did not end there. Bushmaster bought the investment company Freedom Group, in the portfolio of which by then were already Remington Arms and DPMS. Therefore, the military knows this rifle under the name Remington ACR, and civilian shooters – like Bushmaster ACR.

The military purpose of the rifle is even indicated by its name – Adaptive Combat Rifle, that is, “adaptive combat rifle”. And it was also created as a military weapon, which is worth dwelling on in more detail.

The Russian-language myth that American soldiers are unhappy with their full-time small arms and try to change it to a trophy “Kalash” at the earliest opportunity has no basis. Since the Vietnam War, American gunsmiths have not been idle, and the Eugene Stoner scheme, embodied in the family of M16 rifles and M4 carbines, is now almost perfect. According to surveys conducted immediately after the completion of military operations, more than 80% of US troops returning from the theater of operations are fully satisfied with the capabilities of the M4 personal carbine and the M855A1 cartridge (recall that this cartridge is the lead-free version of the M855).

This is an accurate, reliable and battle-tested weapon, which, according to the statistics of army tests, without intermediate cleaning can produce an average of 1691 shots between delays during firing – and this number of cartridges shot at a time obviously means a lot of scalps.

The fact that Americans are confident in the M4 is evidenced by the following fact: in 2007, the US Marine Corps ordered the officers (up to lieutenant colonel) to carry an M4 carbine instead of an M9 pistol by special order. In accordance with the doctrine of the ILC, each marine is first and foremost a marksman, so firepower training and the training of accurate shooting from standard small arms in the ILC pay great attention. As of 2013, only 80,000 M4 carbines were used in the United States Marine Corps, and over 500,000 were used in the ground forces. These carbines almost completely replaced submachine guns from military use, since the widespread use of personal protective equipment makes them ineffective on the modern battlefield.

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There is no weapon in the world that could not be improved in any way.

At the same time, there is no weapon in the world that could not be improved, and the Americans are constantly working in this direction. The Pentagon traditionally went in two ways: on the one hand, together with the M4 manufacturers they created and adopted the M4A1 variant; and on the other, they began to look for a replacement carbine M4, which could significantly surpass it. In 2010, the US Army announced an open competition “Individual Carabiner”, during which it was supposed to consider all promising developments and choose one that would show the most significant tactical and technical advantages compared to the M4.

Such government initiatives are perceived ambiguously, not only in our area. Evil tongues say that the competition, which was held for three years, was initially biased, and the requirements for the weapons participating in it were formulated in favor of M4A1. Be that as it may, its conditions are as follows: the carbine should have fully two-way control and the ability to semi-automatic and automatic firing, work with 5.56 NATO or 7.62 NATO calibers (other calibers were also allowed, but the costs of re-equipping cartridge production would be borne by carabiner developers shoulders). And, of course, have decent accuracy when firing single shots and bursts at ranges from 25 to 300 yards, and also show guaranteed high reliability.

Detailed inspection

Thanks to its legendary halo, “live” Bushmaster ACR does not leave anyone indifferent. Any shooter who at least briefly holds this rifle in his hands tries to kiss, cock, and idle. And after a few minutes, everyone begins to share their impressions – someone violently, someone more restrained. One thing is for sure: there haven’t been any ACR returnees in silence or with the words “uninteresting”.

In black Bushmaster ACR looks quite aggressive, as befits the heiress of the title of Black Evil Rifle in the new century. In the sand – rather smartly. Arrows familiar with the ergonomics of the M4 / AR-15 carbines immediately mark the double-sided fuses and eject buttons of the stores, the layout of which is familiar and familiar. But the shutter delay key has moved down to the trigger guard. It is also double-sided and allows you to control the shutter with the finger of a shooting hand – not only to remove it from the delay, but also to force it on if necessary. The original AR-15 had to use additional devices for this – like Magpul B.A.D. Lever.

But the most important improvement in the ergonomics of weapons is the cocking handle. Unlike not everyone has a convenient rear location for the M16 / M4 / AR-15, here it is brought forward, on the forend. At the same time, the handle itself can easily be rearranged to the other side (it was initially installed on the left). And, most importantly, when shooting the handle is stationary – unlike, for example, the FN SCAR. Many SCAR shooters remembered very well that it is better not to hold a hand on the forearm in this place. In the case of Bushmaster ACR, there are no such problems.

The upper receiver of the rifle, aka “apper”, is made in ACR as a single unit with the upper part of the forend. This made it possible to place a monolithic Picatinny rail on top – for the entire combined length of the forend and receiver. As for the lower forend, there are several varieties for ACR – plastic MOE or metal with Picatinny rails in the Enhanced version. The first is a little easier, the second is more universal. The lower forend is fixed with a single pin, after removing which access to the trunk and its fixing unit in the receiver is opened. The barrel of the rifle along with the gas system is hung out and does not touch the forearm.

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To remove the barrel, you need to open the bracket of the barrel nut, squeeze the locking button in the receiver and turn the nut counterclockwise. After that, the assembly of the barrel with a gas piston is quite easily removed from the receiver (although the first time you may need the help of a mallet). Do not forget to just take the shutter – with the shutter closed, of course, the barrel “does not want to be removed.” In general, for such manipulations it is better to first disassemble the rifle.

Someone will ask: why do you need to remove the trunk? The fact is that the Bushmaster ACR rifle was originally conceived as a multi-caliber system in which, with the help of a simple barrel and shutter larva replacement, it would be possible to quickly switch from 5.56×45 caliber to 6.8 Remington SPC, or even 7.62×39 in general. However, the reality is that currently the civilian shooters are offered the only version of the barrel for ACR – light heavy profile, with a groove, caliber 5.56×45 (.223 Remington) and a length of 16.5 ″.

As a result, those who would like to have a shorter weapon on the basis of ACR, turn to the services of gunsmiths – to cut the standard barrel to the required length (shorter than 10.5 ″ still will not work – the gas block will interfere). Well, in our conditions, a removable barrel makes it possible to greatly simplify its cleaning. Yes, and in the case of a “shot” of the barrel, that is, a significant deterioration in its accuracy characteristics due to wear and tear, reassigning the ACR will not be difficult – you just need to rearrange the gas piston system on a new barrel. Read more about it below.

So, the Bushmaster ACR barrel has a 5.56 NATO chamber and a twist (rifling pitch) of 1: 9 ″, which is perfect for firing the most common bullets weighing 55 to 69 grains. From some owners of the AR-15 rifles you can hear lamentations: they say that the twist is 1: 7 ″ in the military trunks, not like ours – it’s probably better! In fact, the use of grooves of great steepness for the military is an obvious necessity, since it is precisely this step of the grooves that is required to stabilize the long bullets of army munitions, which have an armor-piercing steel core, as well as tracers.

Such cartridges are unavailable to a civilian shooter (and they are not needed), and bullets with an all-lead core with the same mass will always be significantly shorter, therefore they will not require a steep twist for stabilization. Twist 1: 7 ”can be claimed only in the case of long match-type bullets weighing 75 grains and above – but such bullets must be dispersed very smoothly due to increased pressure during firing, which requires a long barrel.

For trunks with a length of about 16 ”, the use of long match bullets completely loses its meaning – the lack of initial speed completely eliminates all their ballistic advantages. In addition, with the steepness of the rifling, the pressure developed during firing also grows, which leads to accelerated thermoerosion of the barrel and increased loads on the mechanisms of the weapon. It’s no coincidence that long-distance truck athletes using long-barreled modifications of the AR-15 rifle in National Match, High Power and F-Class competitions to launch 80-sided “nails” into the distance are limited to only 1: 8 rifling step.”

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For the same reason, by the way, .223 caliber varmint rifles with a longitudinally-sliding shutter use a combination of gentle twists (1: 12-1: 14) and long barrels to achieve a flat trajectory for a high-speed light bullet, in which small errors in determining the distance to the target will not be critical. And, finally, a more “cool” twist negatively affects accuracy – this is a fact proved by ballistics. To summarize: according to the author’s deep conviction, it is the 1: 9 twist for semi-automatic carbines such as AR-15 or Bushmaster ACR – this is the very middle ground.

Bushmaster ACR barrel was manufactured by cold forging; steel carbonization process is used as a protective treatment. The resulting coating, called Melonite, eliminates the need for barrel chrome plating (which usually impairs accuracy), improves corrosion resistance, and significantly extends barrel life. Recently, more and more arms companies are switching to carbonitriding the barrel, considering it the most advanced and efficient technology.

The plastic bottom ACR receiver is impact-resistant, not afraid of heat and frost, and not subject to corrosion.

The muzzle of the Bushmaster ACR barrel is crowned by an AAC flame arrester with a thread for a quick-release muffler. Unfortunately, there are no muffler models compatible with this arrester on the civilian market of Ukraine, and therefore, if necessary, install a third-party – for example, high-performance Finnish silencer Ase Utra SL7 – the AAS arrester will have to be removed.

Yes, and as a DTC, this flame arrester does not work, so you will definitely want to dismantle it to replace it with something more effective shooters-athletes. However, certain problems may arise with the realization of this desire: the flame arrester is mounted on a strong thread lock, and without tools and heating it will be difficult to remove it without damaging it. Meanwhile, the ACR barrel muzzle is the same as most AR-15s – standard ½-28 TPI.

The ACR cartridge ejection window was not equipped with a shutter of the M16 type. Also on the upper receiver there is no notorious shutter rammer. If necessary, close the shutter with Bushmaster ACR using the cocking handle, but with the M16 / M4 / AR-15 rifles this option is not possible constructively.

Let’s go further. The bottom receiver and rifle butt are made of polymer – proprietary Magpul polycarbonate plastic. Actually, all plastic parts for ACR under the contract are produced by Magpul. This plastic is lightweight and shockproof, it is not afraid of heat and frost, it is not susceptible to corrosion and oxidation, and it tolerates moisture without problems – in other words, it is practically eternal. In those nodes where increased loads and wear are possible (USM mount, rear pin of the upper receiver), the plastic is reinforced with steel inserts.

Interestingly, unlike the AR-15 of the Bushmaster ACR, the pistol grip is integrated into the lower receiver – and therefore it is not replaceable, which is somewhat strange for a rifle positioned as adaptive. However, it feels like the handle bearing the Magpul brand and resembling their MIAD model is quite convenient, and its internal cavity is closed by a lid and can store a spare battery, a Bore Snake broach, and the like small accessories.

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USM rifles are generally enclosed in their own metal case. The Descent of the Bushmaster ACR is military-like and quite heavy. For hunting, this is probably just right – a random shot in the excitement of hunting is practically impossible, but for sports use it leaves much to be desired. The USM unit itself is different from the standard one for the AR-15, so replacing it right away will not work. But advanced ACMs are also being released for ACRs – in particular, the legendary Geissele company produces a two-stage Super ACR Trigger, optimal for accurate shooting.

The fire mode switch (in the civilian version – fuse) is also made of plastic. Like the AR-15 (as well as many other examples of American small arms – for example, the legendary M1911 pistols or the no less legendary Remington 700 rifles), the Bushmaster ACR rifle does not become fuse if it is not cocked, which for those unfamiliar with American weapons cause surprise. However, those who worked with M4 / M16, this behavior of this node is just more familiar – because, apparently, they decided not to change it.

Let’s move on to the butt. The ACR Enhanced version has a telescopic butt with a lifting cheek. In the original, it is also folding, however, the features of our legislation forced to block the mechanism of its folding, thus providing scope for creativity for craftsmen. Butt plate – rubber, soft. 7-speed length adjustment, small cheek lift – only 8 mm; however, for most popular collimator sights, this should be enough.

The butt module itself is removable: to remove it, you need to open the upper receiver and pull out another pin that fixes the butt block directly in the lower receiver. Unfortunately, this connection is not reinforced with a steel insert, and there is a noticeable backlash in relation to the receiver – albeit small, but it is. In general, such backlash – the buttstock relative to the lower receiver, the lower receiver relative to the upper – annoy shooters since the advent of the AR-15.

But for some reason, neither in the new versions of the M4 — neither in the FN SCAR nor in the Bushmaster ACR — the gunsmiths pay due attention to this issue, leaving their elimination at the discretion of the shooter himself. Apparently, this is considered insignificant. Nevertheless, the butt itself feels very durable and made to last – at least the owners of the FN SCAR are usually jealous, because with their external similarity, the butt is much more flimsy.

As befits a modular rifle, there are several stock options for the Bushmaster ACR. In addition to the already considered telescopic folding, there is a fixed version, as well as a special version of Magpul PRS – a stock for precise shooting using an optical sight, which has convenient cheek height and overall length adjustments.

More importantly, the PRS will be more massive than the other two options – which means it will provide the best balance for a DMR (Designated Marksman Rifle) rifle with its long and heavy barrel. Well, for those who can’t live without their beloved buttstock from AR-15, American craftsmen have already launched the production of adapters for installing the M4 recoil buffer pipe on the Bushmaster ACR – and, accordingly, any butt model on it.

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On the butt, receiver and forearm of the rifle there are nests for quick-release swivels – you can say, along its entire length. And those who do not trust this system can use the loops for a standard belt. Although it would be somewhat strange to use a Magpul authorship rifle without a wonderful Magpul MS3 or MS4 belt – they are, in fact, “native” to her.

Bushmaster ACR Automation System

With Eugene Stoner’s light hand, rifles of the AR-15 type, including M4 carbines, remain unique – in the sense that this is one of the few varieties of modern small arms, where the powder gases are fed directly to the receiver when the automatics are working.

Such a solution, of course, simplifies the design, while simultaneously providing additional bonuses such as high potential accuracy of fire and low retraction of the aim line, but it also causes a considerable number of problems associated with increased contamination and the need for frequent lubrication, which generally reduces reliability. Therefore, all rifles claiming to replace the M4 carbine in the already mentioned competition “Individual carbine” are equipped with piston exhaust systems. Bushmaster ACR is no exception here.

The ACR gas piston is mounted on the barrel and is held by the gas block and an additional coupling. This piston has a short, within 10-20 mm, stroke. When fired, a rather massive piston with a powerful push transfers the energy of the pressure of the powder gases to the bolt frame, which, moving back along the guides in the upper receiver, unlocks the bolt and compresses the return spring. The bolt releases the cartridge case and captures a new cartridge – there is nothing new here, the larva and generally the kinematics of the bolt are similar to similar elements of AR-15 rifles.

Interestingly, the gas piston is equipped with its own return spring, and quite unusual – from a square wire. Apparently, this was done to get more power.

The gas block regulator has two positions: S and U, that is, suppressed and unsuppressed, respectively, for firing with and without a silencer. This is a very useful adjustment, because when shooting with a silencer, the gas pressure in the system is much higher than usual, which leads to an increased load on the mechanism. With Bushmaster ACR’s adjustable gas block, this problem is completely eliminated. The regulator key is easily translated with your fingers, in extreme cases – with the help of a bullet nose. Another position of the regulator allows you to quickly disassemble the gas unit for cleaning.

Returning to the design of the shutter and the shutter frame, first of all, it should be noted the simplicity of disassembling these nodes – no tools are needed for this. In general, to disassemble the Bushmaster ACR for cleaning and care, the arrow will have enough bullet nose in the cartridge – and this is a good tradition that American gunsmiths honor with the AR-15. Here, this approach is almost perfected.

The bolt frame differs significantly from the AR-15 systems, more reminiscent of a similar part of the FN SCAR rifle. It is milled from a single bar of steel and is very weighty. In the upper cavity of the bolt frame there is a return spring and its guide, in the lower cavity there is a shutter larva and a hammer.

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Interestingly, not only metal parts are used in the design of the shutter frame and shutter larvae. On the head of the pin fixing the striker in its shaft, a sealing rubber ring is provided; and the necessary elasticity of the extractor is achieved by combining a steel spring and a rubber insert. The designers argue that in both cases the system is fully functional without rubber elements, and even in the event of their loss or failure, the rifle will work. However, they are useful for extending the life of other parts – and therefore, if damaged or lost, they should still be replaced with new ones.

This brief description of the design and features of the rifle, I think, can be completed. Much could still be said here, but the real shooter is always more interested in the main thing: what is the weapon in business? And you can answer this only with test shooting.

How to feed Bushmaster?

The main question for any semi-automatic rifle is how “omnivorous” it is, that is, how it copes with all varieties of ammunition of the corresponding caliber sold on the civilian market. Therefore, the first thing we tested was this aspect – for which, after loading one magazine with .223 Rem rounds produced by TulAmmo, Mesko, Sellier & Bellot, Geco and Black Hills, respectively, we went to the shooting range.

We are pleased to note that all of the Bushmaster ACR’s “menus” offered by us were swallowed without choking, and even seemed to ask for supplements with all our looks. Examining the sleeves, we noted that on the bottoms are clearly visible traces of the ejector. This, however, does not mean excess pressure – since there were no other signs like flattened capsules. In addition, marks were present on the cartridges of all shot cartridges, regardless of the manufacturer – apparently, this is just a feature of the Bushmaster ACR automation, and no more.

The supply of the cartridge from the magazine is correct: if you remove the cartridge from the chamber, then no damage to its pool or cartridge case is observed. At the same time, when disassembling the rifle for cleaning after test firing, we noted on the bolt group a certain amount of brass dust – small particles “planed” from the cartridges. Apparently, the new rifle, like any mechanism, just has to go through a small run-in. By the way, about cleaning: Bushmaster did not repeat Colt’s mistakes and assured that the rifle doesn’t need to be cleaned at all, but the pollution really turned out to be small.

And most importantly – the manual explicitly states that the ACR rifle is designed to work “dry”, and it is expressly stipulated that the grease is shown to it in quantities significantly less than the AR-15. And if many owners of the M4 / AR-15 carry the oiler right with them in the pistol grip cavity, it is better to fill the ACR with oil than pour it – the drier the bolt group, the less dust and sand will stick to it during the shooting process.

Now about personal impressions. Working with the Bushmaster ACR is really very pleasant: the controls are placed thoughtfully and conveniently, the shutter handle is exactly where it belongs. When emptying a Magpul PMAG Gen III type magazine, the rifle would become a slide delay.

Store replacement and removal from it can now be performed in one motion instead of two, as on the AR-15 – and this is a saving of precious fractions of a second, during which the shooter is completely unarmed. Some questions arose only to a double-sided fuse – it switches too easily, and several times when manipulating a rifle with gloves, he involuntarily turned on during the shooting process. It is worth following up on this.

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The abundance of places for swivels made it possible to comfortably fasten the Magpul MS3 belt, and on the lower forend bar you can install an additional control handle – a straight one, like Magpul RVG, or inclined Magpul AFG. This will improve the balance of the rifle, the center of mass of which is slightly biased forward, and will make controlling it more comfortable.

You can, of course, use accessories from other manufacturers, but I wanted to pay tribute to the original authors of this rifle. Yes, and why invent something else, because Magpul accessories are upscale, have proven themselves and are well-deservedly popular with a huge number of shooters around the world.

To check the accuracy, we equipped the rifle with bipods and a Nikon LRT 2.5-10 × 40 optical sight. The sight with an integrated laser rangefinder and ballistic reticle for the .223 caliber fits Bushmaster ACR perfectly, transforming it from an assault rifle into a support sniper rifle. Here, the main advantages of ACR compared to the AR-15 were manifested – the sight does not interfere with the cocking handle, and you can place it on the portion of the upper bar where it is most convenient.

To find out the potential of Bushmaster ACR when shooting at medium distances, we went to the firing range. A group of 5 shots at a range of 300 m was frankly pleased: 9 cm in five shots (of which 4.5 cm in four). This, in fact, is the “minute” accuracy: 1 MOA at a distance of 300 m corresponds to a linear 87.3 mm. Such accuracy is considered quite a decent result even for bolted rifles – and yet we are talking about semi-automatic weapons without any claim to “precision”.

After removing the standard arrester, which required some effort, a more effective DTK was installed on the rifle, and then the Ase Utra SL7 muffler. The muzzle brake made it possible to completely remove the rifle’s jump during firing – the linear recoil of the Bushmaster ACR is negligible even without a DTK. Thanks to the silencer, it turns out to train in a dash without headphones – and they become not only needed by the shooter, but also by others, which the latter greatly appreciate.

At the same time, switching the gas block regulator to position S made the clang of the rifle mechanism quieter, since in this mode fewer powder gases act on the automatics. The only hitch occurred when using TulAmmo cartridges – apparently, due to the insufficient weight of gunpowder, their energy was not always enough to reliably recharge when the regulator was in position S, as a result of which the shutter shells were correctly thrown out, but the new cartridge was not fed, since the shutter group after the shot did not reach the rear position.

This problem is eliminated simply: you just need to move the gas block regulator back to the U position, even if the shooting is still conducted with a silencer. And you can do even simpler – completely forget about the use of low-quality extra-budgetary ammunition in modern high-tech weapons.

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This is a compact, ergonomic, technological weapon, designed to shoot in any conditions.

A separate question that interested us: what will happen to the point of impact if you first remove and then re-install the barrel on the rifle? Experience suggests that it will not do without a slight bias, since the sight remains on the receiver. However, how noticeable will this bias be? We shot a test group of five shots, after which we removed the barrel, allowed it to cool and set it back. The average hit point of the next 5 shots shifted by no more than 0.5 MOA (about 15 mm per 100 m), and this value in most cases can be completely neglected.

And finally, the results from the 100-meter line. By selecting the most suitable ammunition from the Bushmaster ACR rifle, groups of 1-1.5 MOA for 5 shots can be achieved. It is hardly reasonable to demand more from a tactical rifle.

21st Century Rifle

Introducing the Bushmaster ACR to Ukrainian shooters, it was called a 21st century rifle. How justified is such a pretentious naming? Well, firstly, ACR was really developed in 2006-2008, so from the actual point of view, this is the development of the new millennium – unlike the M4 or AK. However, the Bushmaster ACR also matches the symbolic meaning of the new era rifle. This is a compact, high-tech, ergonomic, modular weapon, created in such a way as to shoot in any conditions – in dust, dirt, rain, summer heat and winter cold – and with minimal care. And at the same time, which is important, not only shoot, but also steadily hit the target – in any case, the technical accuracy of the weapon allows this. It’s up to the shooter!

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