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There’s always been something about the SCAR rifle series that bothered me. The gun is great — accurate as all hell, runs like a Swiss clock, and easy to use. But the aesthetics of the gun leave something to be desired. Something about the gun always seemed…off. Then I installed the MREX MLOK handguard from Kinetic Development Group, and it was as if the clouds parted and angels had begun to sing. The SCAR had been ‘fixed’ . . .

The SCAR has seemed like something of a chunky monkey. The rail sections on the sides and bottom of the rifle are great, but it makes the gun awkward to hold and visually unappealing. A least to me. FN offers a rail extension kit that gives you some extra railage out past the gas block and improves the ratio a bit, but the gun is still kind of a beast and not for those with smaller hands. What it really needed was a slim and sleek rail extension that would give the shooter more room to grip the gun and also chop out the rail sections (except those that were really needed). Enter Kinetic Development Group.

I had originally contacted the KDG guys to try out their new stock (review pending), and their enthusiastic response was “we’ll just send you everything!” Little did I know they meant one of everything they make, including a MREX rail.

That posed a little problem, though. My SCAR has a barrel that’s too short to take advantage of the rail they sent. I needed a SCAR with a 16″ barrel, and I knew just the schlub for the job. So I packed up some tools (and a few cigars) and headed to RF’s garage to pimp his SCAR.


There’s a little note on the rail when you open it up stating that you should watch an online video before installing it. I promptly ignored that, and it took me the better part of a Cuban robusto to figure everything out. In the end, the rail requires you to remove the existing rail sections from the sides and bottom of your gun, and momentarily un-install your barrel as well to get everything to fit right.

Having tinkered with SCARs before, I was very familiar with the platform and it wasn’t much of an issue, but less technically inclined buyers beware. And watch that video.

Pimped SCAR in action. #guns #SCAR

A video posted by The Truth About Guns (@guntruth) on

When it was finally installed on the rifle, the gun just looks right. At long last the proportions are correct, and the rifle actually looks sleek and sexy. Not at all the blocky and awkward-looking gun that left FN’s factory, it has graduated from frumpy to fabulous.


The MREX rail system comes in two flavors: a 6.5 inch version for 16 inch SCARs, and a 4.9 inch version for 13″ SBR’ed SCAR 17s. Both versions replace the existing rail sections on the sides of the gun as well as along the bottom of the barrel assembly, the main difference is how much additional space they add to the front of the gun. There are two versions of each rail (besides just different colors, available in black and FDE), one using Magpul’s new MLOK system and the other using a screw-in rail section system of some sort. we were sent the MLOK variety in FDE to test out in this case.


Compared to a relatively unmodified SCAR 17, the difference is pretty obvious. There’s a good 1/4 inch to 1/2 inch of material gone from the bottom and sides of the gun, making it easier to hold and slimmer in appearance. There’s a new QD hole out front too, in addition to the existing sling loops on either side of the gas block, for your sling attachment enjoyment. A ton more rail space exists further out beyond the receiver than ever before, and as an added bonus the gas block is enclosed within the aluminum chassis to keep you from burning yourself.

Ask me about why that’s important.


I do, however, have a small issue with the thing: the forward rail section isn’t coincident with the rest of the rail space on the receiver. There’s a distinct dip in the height of the rail, and while that does make the rail slimmer and sleeker it can pose a problem for those who want to mount stuff out there.

I’m of two minds about this specific feature. On the one hand, it makes the rail slim and I like that. But on the other hand it makes the rails uneven, and I like everything to line up. It’s a style choice, and in the long run I think I can live with it, but it’s definitely something to be aware of when choosing the right rail for your SCAR.

Another issue some might run into is the color. No two SCARs are ever the same color really, and that’s all got to do with how long the receivers are in the anodizing tank. Heck, two receivers from the same batch might not be the exact same shade of brown (or FDE or whatever). So just be aware that the FDE on this rail might not exactly match the color on your SCAR. In this case, however, Robert got very lucky.


Something I thought I would hate is the choice to go with MLOK. Everything I own and actually use is currently running the competing keymod system for accessories and attachment rails. I like it better mainly due to the ease of use and ready availability of accessories.

Magpul wants their MLOK system to be the new hotness in accessory rails, and initially I thought it was pretty dumb. I tried it for the first time in the field with this rail, and in my opinion… I still like keymod. But MLOK isn’t as bad as I thought it would be. It definitely gives the extension a better and sleeker look than the odd shaped keymod holes, but putting things on and taking them off can be a pain in the ass. They need to make it a little easier to use, I think.

But I digress. Back on topic.


I like it. A lot. The SCAR was designed with specific requirements in mind, and while it meets those military requirements, that doesn’t always translate into something that the civilian market will find useful. The MREX rail takes that clunky military firearm and adds some style and usability to it for the civilian world, and does it very well.

There’s nothing destructive done to the gun, and you can do it without even reading the instructions in about half a cigar. Robert likes it so much that he’s keeping it on his gun. I like it so much that I’m buying another one for my SCAR, but a little shorter this time.

The MREX rail combined with a different stock on the SCAR completely changes the nature of the beast. It makes the gun slick and beautiful instead of chunky and utilitarian. And I like that.

Specifications: KDG  MREX MLOK Rail for the SCAR Rifle

Lengths: 4.9″ or 6.5″
Colors: FDE, Black
Price: $299 each

Ratings (out of five stars):

Fit and Finish: * * * * *
The rail locks up perfectly on the rifle, with very tight clearances on the receiver parts. The finish is satin smooth.

Ease of Installation: * * * *
Grab a cigar and a laptop, you’ll be fine. Not quite as easy as changing an optic out, but WAY better than adding a rail to an AR-15 M4gery.

Overall: * * * * *
It’s right in the same price range as all the other available SCAR rails, but it’s the only one that actually looks good. Functional and pretty, it’s definitely a keeper.

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  1. Looks interesting. After handling my friend’s SCAR, I do agree that it has a certain amount of unnecessary bulk to it, especially compared to conventional AR-15s, or even the AK series rifles. However, I wonder if the extra rail on the front throws the balance off the rifle, particularly if you are accustomed to the stock factory SCAR.

  2. I never understood hand guards with gas block sight cutouts. It just seems odd to me to have that gigantic gap there for stuff to catch on, break, etc…

    • With the SCAR, the front sight is permanently affixed to the gas block. There’s no way to make a rail that doesn’t have that cutout. I know what you mean on ARs, though — low profile gas blocks exist, we don’t need no cutouts.

  3. So I’m sure someone here can give me a straight answer. Im building my first AR in the upcoming weeks and months, and I want to have a modular rail (for weight saving and comfort over quad rails). So what really is the issue with MLOK?

    • It’s a weight / aesthetics vs ease of use issue. The MLOC is a bit harder to use but weighs less and looks nicer than keymod. It’s a judgement call but neither system is “bad”, it’s just a priority issue.

      Personally, given that I am already heavily invested in Magpul stuff on my various toys, it makes sense for me to stay with them.

    • Probably the biggest is that we don’t know yet which will “win” in the marketplace. Think VHS cs Betamax or Blu-Ray vs. HD-DVD.

      Nobody wants to be left with a box full of gadgets and stuff that you can’t bolt on to the next rifle.

      Both keymod and M-Lok have Picatinny rail adapters available so that’s one option, but it will wind up weighing more than a rail-specific farkle alone would.

      My advice would be to find a local gun shop that stocks both, and will let you try them out with, say, installing or removing a hand grip or flashlight mount

      • Yeah I planned on giving them both a try anyways before I dropped big $$ on a hand guard that I’m gonna be more or less “stuck with”. To your point about the market, its sort of stumping me on this. As far as I can tell, there are more companies producing Keymod rails and key mod accessories. However, damn near everything that magpul puts out there is a success and they are darn good about keeping accessories available and cost effective. Just gonna have to take a leap of faith I suppose.

        • One thing you might do is make a list of everything you think you might want at some point – fore grip, bipid mount, laser holder, light holder, backup sights, coffee cup warmer, etc – and see if you can get all of them in one format, both, or neither. Note the prices, too, so you can see if there’s a noticeable difference.

        • Yeah good call. As on now I’m going for a handstop like the BCM KAG with a nice light mount. The optic should be covered by the rail section on the receiver.

  4. Do you have the machining marks on the most forward section of the MREX rail’s 9 o’clock face (if the clock were viewed from the operator’s POV)?

  5. I feel like if someone is going to drop that kind of coin for a SCAR that it should be perfect from the factory. I shouldn’t have to drop an extra $300 on top of the $$$$.$$ I have already spent. #firstworldproblems

    • Yeah thats what has been my problem with the SCAR. I know for a fact that it is an amazing rifle and it will do the job of a battle rifle very well. The issue is, i can get an AR with a piston system to behave similarly for less $$. The scar is great but it is far from perfect and because it is produced by one company, its pricy and accessories are hard to come by not to mention the issue with the proprietary magazines.

      • The SCAR 16S, reviewed in this article, uses standard STANAG compatible magazines just like your AR-15.

        • Yeah Im referring to the heavy model (7.62×39) but still, i haven’t been able to see what the SCAR does that much better than a piston AR variant of the same caliber.

      • You mean the 7.62×51. 7.62×39 is for the AK47. And the MK16 doesn’t do anything better than the SOPMOD M4A1 with the RIS package. Its why the Rangers dumped the MK16 so quickly, followed by SOCOM as a whole. Their is a reason that CAG and DEVGRU do not use the MK16/17/20s and stick with ARs.

  6. Why didn’t they extend it another two inches to reach the rear end of the barrel threading? If you’re going to make extended handguards for extra hand space, why not go the full monty?

  7. I’m very interested to hear what you think of their SAS.

    As for the lower rail height in front of the gas block, I think that was an intentional design choice to allow you to mount rhino-configuration flashlights, PEQs, etc without interfering with your optics’ sight lines. I kinda like it.

  8. I have both a 16s and 17s. When I got the 17s I was eager to jump on the “pimp out my scar” bandwagon. No-more. The fore-end only added weight out at the end of the barrel. This made the rifle much less maneuverable, IMO and failed to hold zero for long range shots (700-800m).

    The VLTOR RE-SCAR stock adapter, however,was an awesome add-on. This allowed me to get true cheek weld for my Leupold Mark IV scope (The Boot always left me slightly low relative to proper alignment). The storage compartment is also large enough for an emergency cleaning kit/ parts kit (think M1 Garand). It also adds 2 qd sling sockets which are sorely lacking on “the boot”. Nick did a great review on this already

    Anyway, that’s my 2 cents.

  9. The rail looks pretty cool. I wont be adding anything to mine like that. I don’t even plan on changing out the stock. I did add magpul rail covers and it makes the rifle much nicer to hold. I currently have a bipod on it but was running a magpul foregrip. I will be putting some higher quality glass on it in the future.

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