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Evolutionary: Rock River Arms LAR-47 Review

Evolutionary: Rock River Arms LAR-47 Review


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 7.62x39 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 5.45x45 (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 7.62x39 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 7.62x39-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 7.62x39 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.

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The fact that this rifle doesn't require an adapted AR magazine to feed 7.62x39 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 7.62x39 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 7.62x39 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 7.62x39 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.


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.

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