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Evolutionary: Rock River Arms LAR-47 Review

by Eric R. Poole   |  September 24th, 2012 18


If you’re as fanatical about ARs and AKs as I am, you’re probably sitting there physically aroused. (One second, let’s check… Yep.) Don’t be embarrassed; you have every right to be worked up. The new Rock River Arms LAR-47 is nothing less than an engineering marvel. A number of companies have already tried to work through the problems associated with breeding an AR and an AK, but the results have usually been comparable to kissin’ cousins getting it on (the baby might walk, but you just know there isn’t something right about that child).

Designing an AR lower to accept an AK magazine is more complicated than you might assume. Rock River started from scratch.

“For years, different companies have been trying to make a 7.62 AR in one form or another,” says Steve Mayer, new product manager for Rock River Arms. “We’ve seen everything from an AR mag with a different follower to a frankenmag with an AR magazine top half and an AK magazine on the bottom half. The magazine has always been the AR’s weakest link. We’ve been looking at this for a number of years, but in 2011 we decided to take advantage of what we were good at. We’re not a magazine company, we’re a rifle company.”

The design challenges for Rock River were in working around the multiple variations of the AK magazines (not all AKs are like the AK) and the fact that bore diameters vary for 7.62×39 ammunition. American ammo manufacturers typically use a .308-diameter bullet when loading 7.62x39mm cartridges, while Europe, Asia, the Middle East and Russia typically use an inconsistent variety of bullets with a .310 or .311 diameter.

Once these challenges were defined, other decisions like choosing a barrel twist were a little easier. (Barrel twist was a nonissue, as Rock River simply chose to go with the 1:10 RH found in most AKs.)

Standard Configurations
About the only feature you can’t change with the LAR-47 is the barrel and gas system. No, you can’t order one in 5.45×45 (yet), but it does feature a 16-inch, chrome-lined heavy barrel. And though the AK is a piston-driven rifle, the LAR-47 retains the AR’s conventional direct-impingement gas system.

“The piston system we’re running wasn’t compatible for this rifle,” says Mayer. “We had to put that aside for the time being. Direct impingement is common in most of our products, and we know that it works in this one.”

Yes, cheap imported 7.62×39 ammunition can cause fouling faster than American-branded ammo and the 5.56, but that’s why Rock River standardized a few features.

“Chroming the bore and bolt carrier on production guns is standard,” says Mayer. “The biggest issue you’re going to have with dirty ammo is shooting it and leaving it dirty. I always assume that if it says 7.62 that it’s going to be corrosive ammo, and I’ll clean it anyway. Chroming is what Rock River decided it could do to help the customer.”

Rock River currently offers two different configurations, but it welcomes a customer’s preferences when ordering through a dealer. Priced at $1,200, the entry-level LAR-47 features a basic A2 birdcage compensator, the A2 front sight post assembly, two-piece carbine handguards, an A2 pistol grip and an M4-style six-position collapsible stock.

I evaluated the LAR-47 Delta Carbine. At nearly $1,500, it may be three Franklins more expensive, but you get Rock River’s effective Delta muzzlebrake, a two-piece quad rail, a Delta pistol grip and Rock River’s new six-position Delta stock. Descriptions of these optional features can all be found online at or through other reviews. So let’s get to what makes the LAR-47 unique.

New Receivers
Being that most ARs are close adaptations to Eugene Stoner’s design, I’ll stretch my neck out to suggest that this is the most significant success in altering the AR for a different purpose. To pull off this achievement, Rock River had to start over and design a new billet upper and lower receiver, seen on prototypes at the 2012 SHOT Show. Actual production guns will be forged.

The lower receiver has been carefully engineered to accept the 7.62×39-type AK magazine while retaining all of the ergonomic advantages that the AR platform is known for. Since an empty AK magazine won’t trip a bolt catch, Rock River was able to eliminate it and give the magwell the room it needed without cutting into the trigger group housing. (This means you can still change out the standard trigger swap for a special one.)

Unlike an AR, AKs have a long, protruding firing pin designed for a hard strike on the variety of cheap surplus ammunition with inconsistent primer depths. Rock River alleviated problems with hard primers by incorporating a heavier hammer spring and modifying the bolt carrier group. Besides that, nothing else had to change to ensure reliable ignition.

When you’ve emptied your mag, the bolt still closes on an empty chamber. It may be a criticism, but it does give the AK another nod toward honoring its function. (Being that there is no bolt catch, it’d be nice if Rock River surprised us with a model featuring a forward-located charging handle to more comfortably hold the action open or quickly rack the bolt with.)

The new magazine well is immense. Rock River chose to incorporate the AK’s magazine hook-and-latch system, so you have to insert the front of the magazine in first before rocking it back and locking it in place. This addresses one of the Achilles’ heels of the conventional AR platform. With the AR’s spring-loaded crossbolt magazine catch design, the standard AR magazine has a considerable amount of lateral play. The barrel extension has two narrow feed ramps to accept cartridges from either side of the alternately feeding double-stack magazines. If the magazine’s feed lips are out of spec or if lateral play becomes too extreme, the bullet nose can be misaligned with its feed ramp, contributing to a malfunction. The benefit of Mikhail Kalashnikov’s design is that the front of the magazine is hooked and kept in place behind a wide feed ramp. Even if the AK magazine experiences lateral play, the bullet nose always has a proper orientation and clear path into the chamber.

To disengage a magazine from the LAR-47, you have to press forward on the magazine-release lever that’s accessible from either side of the triggerguard. With the geometrical angle of the AK magazine shifting its profile forward, Rock River had more room to increase the room within the triggerguard. This forged piece of aluminum is clear and out of the way from the magazine-release paddle and helps speed up magazine changes.

Both upper and lower receivers had to be modified to make room for the wider and longer feed lips of the AK magazine. The bottom of the bolt carrier group was specifically cut to accommodate the AK magazine feed lips. The geometry of the bolt and feed ramps of the barrel extension were also adapted for the larger 7.62 round and its increased pressure. These modifications ensure optimal reliability and are often passed over by others who have tried to take shortcuts in adapting an AR to chamber either the 7.62×39 round or an AK magazine. Interestingly, the LAR-47 didn’t need a new buffer and spring assembly to run right. And though these receivers are entirely new, they actually measure the same length and width as Rock River’s standard 5.56 receivers.

The fact that this rifle doesn’t require an adapted AR magazine to feed 7.62×39 is awesome. AK magazines just work better and are built stronger than the USGI-type mags. For those of us who have worked with ARs chambered for the Russian round, ARs tend to be picky with what magazines work and which ones don’t. Those of us who have converted an AR to shoot 7.62×39 also had to buy a surplus of magazines in order to sort out the 50 percent that didn’t reliably feed. Of those that work, many will only feed 10 rounds before jamming the action. Most AR magazines I’ve seen converted to 7.62 won’t carry 30 rounds, and if you stuff a magazine to max capacity, reliable feeding of the first few or last few tends to be in question. What’s never been in question is the fact that AK magazines work splendidly with the 7.62×39 and hold 30 rounds.

Obviously, the LAR-47 accepts AK magazines. Well…most of them, anyway. During this evaluation, I tested the rifle with every variety of AK magazine I could find: Bulgarian, Chinese, East German, Russian and so on. As far as polymer magazines are concerned, the LAR-47 included two U.S.-manufactured magazines from Master Molder that worked perfectly.

You might be thinking that going with plastic magazines was a strategic decision by Rock River. Obviously, steel AK mags would chew up the locking tabs in an aluminum magwell, but Rock River anticipated this and designed the LAR-47 with a steel crosspin for the magazine to bear against at the front of the magwell. Using surplus steel mags with this rifle won’t hurt it.

Unfortunately, I didn’t obtain a U.S. PALM magazine ahead of this test, but I did try a magazine from Tapco. To me, it was no surprise that it didn’t work. I have experienced many problems while attempting to insert a Tapco magazine into an actual AK. Though they are rigid, the magazine body is usually molded too large for the typical AK magwell. And now this extends to the LAR-47. With force, I was able to insert the Tapco magazine about halfway, but once I got that far with such difficulty I was afraid that I wouldn’t be able to remove it if I managed to lock it in place. I gave up on the attempt and accepted the fact that this rifle won’t take an AK mag from Tapco.

The verdict is still out on drum magazines. We had a couple to try, but neither worked. This doesn’t say anything, because they won’t work in any of our AKs either.

Range Day
The AR has always had a lot of desirable benefits going for it. For one, you can easily attach a modern magnified optic for precision shooting. For iron sight users, there’s more sight radius between front and rear sights with an AR, which means a better sight picture will enable tighter groups. Most of us would love to hear that the LAR-47 is a rifle that now offers AR accuracy with AK ammunition. Unfortunately, this just isn’t the case. The LAR-47 does produce better accuracy results than the common AK, but so many ARs on the market are capable of sub-MOA five-shot groups due to enhanced operating systems, match-quality barrels and accurate bullets with high ballistic coefficients.

In testing, I put a little more than 500 rounds of high-quality ammunition through the LAR-47 and about 50 rounds of Russian 123-grain surplus ammunition I picked up at my local gun store. The surplus ammunition averaged 2.11 inches, which is typically a “good” group fired from an AK. The best accuracy came from a box of Hornady steel-case match ammunition I had left over from another project. Though I produced a pair of groups that averaged 1.26 inches, I couldn’t include it in the accompanying accuracy table. Unfortunately, I didn’t have enough ammunition for five five-shot groups to complete the chronograph segment.

The brass-cased ammunition from Remington and Winchester produced virtually identical results. Though Winchester had a slightly better extreme spread of only 30 fps across the chronograph, Remington’s 123-grain FMJ grouped five averages of five shots in 1.6 inches from 100 yards. With Winchester printing an average group of 1.8 inches, this is going to be fairly representative of what you can expect from the LAR-47 until Rock River decides to free-float the barrel.

Gun of the Year
Being that this model is called the LAR-47, many have already asked why Rock River didn’t simply offer this rifle with a piston system. The price was already high enough. After discussing this matter with Rock River, I’d like to suggest that you not be surprised if a piston variant eventually appears as well as one chambered for 5.45x45mm, but they had to start this series with a basic and a slightly enhanced model affordable to the masses.

“A model in 5.45 is entirely possible for 2013,” says Mayer. “It would require different forgings that were caliber specific, particularly the lower. But it wouldn’t surprise me.”

Regardless of what models Rock River decides to follow up with, the LAR-47 is the most interesting new introduction to come out of the firearms industry in 2012. Many of us have access to plenty of 7.62×39 ammunition, and spare mags are still readily available. The idea of an AR-AK is one that all of us secretly admire, and this one is easy to get into bed with, with little extra investment after the point of sale. Go ahead and admit it. You want one.


A Leupold CQBSS 1.1-8x24mm was selected for accuracy testing and function firing. It maximized the cartridge’s usefulness at short ranges and revealed the accuracy limitations of the 7.62x39.


10GAAR12__03145_stdBook of the AR-15 has all the information you could possibly need about America’s favorite semi-auto rifle. From gun and gear reviews to commentary, Book of the AR-15 is your go-to source for everything AR.

  • SamF1911

    I'll admit it. I want one really bad.

  • Mike

    With the rapid disappearance of the cheap surplus 5.45×39 and it's general replacement with Wolf or Tula ammo that runs the same price as it's 5.56×45 counterpart, there is literally no point in Rock River making a 5.45 model. AK-74 mags are scarce and if there is no savings on ammo and no ballistics gain (and I would argue there really isn't), then there is no reason to buy it.

    Also, the author mentioned he tested with 500 rounds of "high quality" 7.62×39 and 50 rounds of "surplus". Now, first of all, did he mean surplus or does he mean new manufactured steel cased Eastern European ammo (again, Wolf, Tula, Brown Bear, etc)?

    Also, given the way most AK shooters operate, why would you conduct the bulk of the test with 500 of rounds of Remington or Winchester? I know of virtually no AK shooter who does that, mainly because the ammo is twice as expensive and the guns don't really show much gain from it. This so much the case that I can't even tell you the last time I actually saw brass cased 7.62×39 on the shelf anywhere? Tula pretty much rules the roost now, with the occasional appearance from Wolf or Brown Bear.

    Now I would understand if the author wanted to show what this AR is capable of, but since one of the specific points he mentioned in the design was that it was designed to handle "dirty" ammo, why wouldn't you have the bulk of the ammunition tested being the dirtier surplus or Eastern European steel cased? That would actually indicate how well the gun performs under conditions they are likely to run it in. Then he could have shot 50 or 100 rounds of the brass cased "good stuff" to test accuracy.

    This article left a lot to be desired (and really, there is no need to mention your erection… ever).

    • Kirk Noteboom

      @ "handle "dirty" ammo"

      The AR will have trouble with dirty ammo. Carbon buildup is bad for any semi-auto. I want a 7.62×39 that has dependable accuracy at long range with a scope mounted on the receiver. When I get one it will fire brass cased copper jacketed ammo that shoots tight groups. I will not be on the battlefield stuck with whatever I pick up. But if "Red Dawn" happens then whatever crap they use on us will have to be good enough. I will just have to clean it like a good solider. This weapon needs an 18" or 20" barrel with a ridged free float rail system before I buy one.

  • @Lakan_Kildap

    It's a new gun, basically, so I guess Poole started with high quality ammo to get a general idea of whether it will actually run. If it doesn't run even with good ammo, it's junk. If it runs with good ammo, the next phase of stretching the design is to test it with cheap ammo. And so on.

    Also, Remchester were mentioned in the accuracy part, I think it was to show the best that the gun can do.

  • shawn douglass

    I liked that Rifle the first time I saw it, when it was called the Knights Armament SR-47. Good job 'inventing' RRA!

    • Kirk Noteboom

      You can't buy the Knights Armament SR-47!!!
      I think this is a step in the right direction. This will show that the ACC 300 Blackout is no where near the power of a real 7.62×39 AR.

      The SR-47 is based on the Knight Stoner Rifle (or SR) series. Many aspects of the rifle resemble an M16, but almost all parts are upsized slightly to handle the larger 7.62x39mm cartridge. It uses standard AK magazines and the magazine well is modified to accept standard box magazines.

      Only seven rifles are known to exist. Six went to USSOCOM and one was retained in the Knight Co. museum.

      The rifle uses a custom barrel manufactured by Obermeyer Barrel Co. of Wisconsin. It is machined to accept a custom Knight manufactured suppressor.

      In 2012 Rock River Arms began marketing a civilian rifle very similar to the SR-47 called the LAR-47

      • frank

        LOL, "This will show that the ACC 300 Blackout is no where near the power of a real 7.62×39 AR."

        • Kirk Noteboom

          LOL "frank"
          The ACC 300 Blackout can only push 125gr bullets to 2100 fps but the 7.62×39 can run that same bullet weight at 2400 fps without excess chamber pressure. If you use a SBR the velocity difference is less but this is not a SBR. You believe in propaganda and misinformation in you think I'm wrong.

  • Joe

    Anyone know when this is going to be released/for sale.
    Everytime I email RRA all I get from them is they don't have any dates yet?
    Whats up with that do they want to sell it or not because if the SIG 516 Russian in 7.62X39 comes out first then I will buy that one.

  • Mack Missiletoe

    I want that wood box and ammo.

    I would use it in a CZ 527 Carbine… or sell the ammo. I need ammo money! hahaa…

  • Larry Petro

    What was RRA thinking when they produced a 7.62X39 with a direct-impingement gas system? The worlds all round dirtiest ammo mated to a system that puts a large portion of that fouling directly where it can do the most harm. My jaw dropped when I saw this weapon on their web site. I think RRA builds a great weapon with possibly the best "out of the box" trigger on any tactical rifle. BUT this ammo/operating system combo is sheer madness.
    Now take a look at the Sig 556R. A piston operated weapon based almost totally on the AK design. Sigs first evolution of this weapon had several design and QC flaws that gave it an initial bad rap, but those problems have been corrected. What you now have with the Sig is a weapon that will function with real world AK mags and any ammo you can feed it, from expensive name brand to battle field pick-ups. Get the SWAT version with the quad rail, change the buttstock to a buffer tube, mount your choice of AR buttstock, add a decent optic, and you are literally ready to rock and roll. Wake up RRA.

    • Kirk Noteboom

      The Sig 556R is just an improved AK.
      The Sig 556R also has a bad history. When you sell guns that suck and then go back to build them right is just a very bad idea in my book. If you buy the Sig 556R and don't like it you will have a very hard time selling it with that bad history.
      I would take and AR over an AK if I had the choice.

      • Ben

        That's ludicrous. If they sell something that sucks then go back and build them right, they are learning from their mistakes and improving. Now maybe they should've done more R&D before the initial release, but to say it's a "bad idea" to improve on your products is just ignorant. The benefit to a 556R is the larger sight picture, ability to mount more accessories to the rails and to have a viable alternative to the run of the mill AK that everybody and their brother has. Another thing of note for those of us that care, is that it doesn't have the same shape as the AK, which is often associated with the "bad guys". The Sig is a good weapon, that definitely has its niche and definitely was a little better thought out than this direct impingement RRA rifle for the same money.

        • Kirk Noteboom

          No Ben it's always a bad idea to sell defective products. That sticks like glue and takes a long time to overcome in the eyes of the consumer. AR's can be built to give much more accuracy than AK based weapons. The scope base of an AR gives a much more reliable and consistent zero when a free float handguard is used. The AR's gas system will also allow for more accuracy because of no operating rod adding stress and vibration to the barrel like an AK. As for the anti direct impingement kooks out there I had to spend a day at the range burning up military ball ammo with my GI issue M16 because my platoon was the last to the range and the range officer had cases of ammo still left and told us to fire it all because he would not do all the paper work needed to turn it back in. We shot for hours until the ammo was gone and none of the weapons had any problems. The weapons of the past that hand gas pistons and operating could bend an operating rod just from hard extraction or overpressure during extraction. If the AK is a much better weapon in your opinion then why do none of the current US military units adopt that action over the M16 when they need a weapon to fire captured 7.62×39 ammo?

          • Kirk Noteboom

            One reason the 7.62×39 ammo is known as dirty ammo is because the steel cased ammo that everyone is shooting is to stiff to expand and seal in the chamber when fired. All that chamber blow by fills the action with carbon and powder fouling. The gas system of an AR blows its gas out the ports in the side of the bolt and very little is added to the action from the gas system. Steel cased ammo will foul the action faster in any semi-auto. One thing that helps the AK eject is the steel cased ammo. The steel case never grips the chamber like brass does but the steel case gives you a dirty action much faster.

  • Lee

    Is this still coming?

  • Lee

    If only it was a long stroke piston design goddamit!!

  • 03disGRUNTled31

    No credit given to Eugene Stoner’s Sr-47 for this blatant slightly-modified copy touted as “revolutionary” and “new.” People truly have rejected history, as they are now men without eyes nor ears.

    How about this, Knights Armament, Rock River Arms, and Faxon Firearms(ARAK-21), all team up and put together a reliably working long stroke piston Ar platform compatible with the Ak-47 mag chambered in 7.62×39 as well as an Ak-74 compatible 5.45×39 platform.

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