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It seems that on every free-floated hand guard review I’ve written, reader Tex300BLK has weighed in strictly to ask me when I was going to test the BCM KMR rail. So I forwarded his comments to the fine folks at BCM and asked real nicely. They happily responded and asked me for my address and a few short days later, I had a 13″ KMR rail on my doorstep . . .


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Billed as being invented by the “Father of KeyMod”, BCM claims that the KMR is light, tough, and strong. And sure enough, upon initial inspection, the first thing you notice is how darn light the rail is. The rail alone without hardware weighs 5.35 oz. which is basically featherweight status. Keep in mind that my test unit was a 13-inch version and that BCM offers 9- and 10-inch versiona as well for those looking to shave even more weight. Folks looking for a lightweight build should surely have their ears perking up at this point.

BCM indicates that they’re able to get such a lightweight 13″ hand guard by using an aluminum and magnesium alloy that sheds 30-40% of weight vs. pure aluminum without sacrificing strength. The full kit including rail and mounting hardware weighs in at 7.6 oz.

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When I emailed Tex300BLK to tell him I had the KMR inbound, he told me that installation was fairly straightforward, but like anything, go slow and take your time. I found installation of the KMR to be easy enough assuming you have all the right tools. If you don’t, a qualified gunsmith should handle the job for you.

The kit includes not only the hand guard and all necessary hardware, but a very robust wrench to help knock off a mil spec barrel nut and replace it with the KMR-specific nut. You’ll also need the tools to remove your gas block from the barrel so you can thread on the new barrel nut.

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The thing I appreciated most about this system is there’s no correlation between barrel nut torque and hand guard timing. This differs from the Noveseke NSR, Strike Industries Mega Fins, and a gang of others which require you to crank down on the barrel nut until everything fits. If you’ve read my Mega Fins review, you’ll remember that Strike includes a series of shims to assist in timing which had the less-than-desirable effect of creating an ugly space between receiver and hand guard.

The BCM system uses a solid barrel nut with a U-shaped channel cut all the way around. This channel is where the two sets of screws that hold the whole thing in place reside. No matter what you torque your barrel nut to, the hand guard will always fit tightly to the receiver, and be perfectly timed.

I’ve never independently tested it, but some people in the gun industry have told me that there’s a correlation between accuracy and barrel nut torque. That claim may or may not be a steaming pile of bull excrement, but if there’s any truth to it, the BCM KMR would allow you to set your barrel nut to your desired torque setting without worrying about having to time the hand guard in place.

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Once the barrel nut is torqued using the included robust tool, the instructions suggest heating up the hand guard with a hair dryer for a few minutes to help fitment. While the hand guard is heating up, the gas block and tube are installed, and screwed in place. After the hand guard reaches optimal temperature, slide into place and install the necessary hardware.

There’s a small metal shim that sits between the hand guard and receiver to ensure that everything is timed correctly, though there’s a little wiggle room to make sure it’s perfect. Your installation experience may vary, but mine required liberal tapping with a 2×4 and a mallet. Once in place, torque the retaining screws in the order specified in the manual and you’re done.

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Altogether, it’s a really fast install owed mostly to the fact that you don’t have to constantly torque and re-torque the barrel nut to get everything timed correctly. Just hit your desired torque spec, get the hand guard in place, and fit the retaining screws. That’s it, you’re done. I managed to do mine in about 20 minutes owing mostly to how slowly I went while following the instructions. I’m fairly certain I could do the next one in just a few minutes.

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But don’t mistake speed of install for being indicative of a less than stellar product. Really the only bitch I have is that the finish doesn’t match the finish of my receiver. Super detail oriented operators may want to call BCM and see if there’s a way to match the finish for the two. In either case, the BCM KMR is lightweight and sturdy as hell. I was unable to loosen it or beat it up in day to day use. Installation of the rail didn’t seem to make my gun any more or less accurate, but it did give me additional mounting positions for accessories with the KeyMod sections at 3:00, 6:00, 9:00 o’clock and all the positions in between. This allows a ton of real estate for lights, lasers, grips, and kitchen sinks. 
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Specifications: BCM KMR 13 Hand Guard

  • Materia: Aluminum/magnesium alloy
  • Mounting: KeyMod interface system
  • Length: 13″ length
  • Weight: 7.76 oz (including mounting hardware)
  • Color: Black
  • Price: MSRP is $300 but you can buy direct from the manufacturer for $269.99 or, yes, Cheaper Than Dirt for $230.23

Installation * * * * *

With a good action vise and a torque wrench, you have what you need to install the BCM KMR. The company is kind enough to include the special tool needed to install the barrel nut along with the Torx wrench necessary to torque the retaining screws in place. The whole installation process is very quick and doesn’t require any torquing and re-torquing of the barrel nut to time the hand guard.

Fit, Finish, Quality * * * * *

The KMR, though light as a feather, seems to be as tough as a rhino. The matte black finish seems to be stout and I wasn’t able to easily scuff it using a set of car keys or a screwdriver. Overall, it looks real nice, and seems real strong.

Accessories * * * * *

From my keyboard commando chair, KeyMod is the defacto standard for modular accessorizing. Yes, M-Lok is a thing, and you should see a M-Lok hand guard review coming, but the world of KeyMod accessories is huge. Literally anything you want to stick on your gun can be found in a KeyMod compatible platform

Overall Rating * * * * *

It isn’t often that I’m absolutely floored by a piece of gear, but the KeyMod hand guard has done it. This thing is so light, so strong, so modular, and so good looking, that it has become my standard for all new builds. I don’t really see a reason to mess around with another type of hand guard when I can get everything I want in one package.

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45 COMMENTS

  1. I love BCM, but that price is retarded.

    For just a couple ounces more, you can have an ALG rail for less than half the drive of that. Come on BCM, you can do better.

    • Considering the sheer genius of how this thing was engineered, I think the price tag is justified. Have you held one in person? It’s genuinely mindblowing.

    • I guess the only question is: what are the practical differences between this and the ALG (which comes in m lok)? Is it only the ounces? is there a practical difference in how securely it mounts? Is there going to be play with my front BUIS with the ALG and not with this? I think i’ll be getting the ALG.

  2. And I’ll be getting one of these now. Always swear by BCM.

    BCM is selling these as complete uppers with a free bolt assembly if anyone is interested. It’s a pretty good deal considering the products are stellar.

    • Yeah at the time I built my upper those items werent included I came out maybe $100 ahead of where I would have if I had bought one of their uppers that came close to the specs I wanted. Now that they include the BCG and their Mod0 Comp (I still prefer the fsc556 but the BCM Mod0 kicks the ass of any other free flash hiders that companies give you right now) as well as discounted price on their gunfighter charging handle. I might go so far as to say that is one of the best values in the AR industry right now when you consider the quality of BCM’s stuff (google “BCM Filthy 14” if you doubt their quality). I was pretty mad when 4 months after I finished my build they were selling the completed uppers with BCG, dicsounted CH and Comp included for the same price as the upper alone was selling for when I built mine. Could have saved a bit of money there. Oh well.

  3. When are you going to review slr rifleworks stuff? I’ve got the 13″ solo lite handguard and like it alot. The only issue I’ve had was installing a bcmgunfighter short vertices grip. I had to loosen the key mod post things to actually slide it into place. I didn’t have any other key mod stuff to check if it was the grip that was the issue or if the rail was to thick.

      • Awesome. Hopefully the set you up with the clamp on adjustable gas blocks. BTW the calamity nick hunting story was great read and very well written.

        • I returned my (not yet installed) SLR 15″ Solo Lite handguard when BCM’s uppers went on sale w/ the free BCG and comp. The KMR is lighter and much more comfortable that the SLR, or any of the other handguards I’ve tried, for that matter.

          I love going into Rainier Arms, but every time I do, I realize just how much my AR-15 sucks, and I feel compelled to buy top end stuff to make it suck less…

        • I just finished mine in October. Meg arms upper and lower, spikes st t2 buffer, wmd guns nib bcg, voodoo innovations 14.5″ evo ultra lite, magpul fcs stock, moe pistol grip, magpul trigger guard, magpul mbus, bcm short virticall grip, bcm gas block, voodoo jet comp and an eotech 517. That was supposed to be a budget build but got expensive real fast. I would go broke if I went to Rainier arms.

    • SLR does their keymod rails thicker so that each slot also doubles as a QD mounting point for slings. This is a very good thing.

      • Ah that explains why I’ve seen other people run qd mounts on their keymod rails and I thought what’s the point if u can run a qd into the keymod slot.

  5. And I see you have the Giesele gas block on there as well, that is looking like a very nice light upper to run and gun with.

    • Still has a 20″ heavy contour barrel so its no daisy to carry around, but it is much better balanced now.

    • The carbine I built with a KMR has a 16″ barrel with very deep flutes, is better balanced than some SBR’s (albeit with big chunky quad-rails) I have shot. If I put my hand right up next to the magwell and the the CTR all the way retracted it still wants to lean to the rear even with no magazine in it and a streamlight TLR2 all the way out on the end. The few times I have “run” it, it was a dream to shoot. I am planning on building a 11″ gun with the caliber in my namesake (still working on my Form1) with either their 9″ or 10″ KMR and I imagine it will be even more awesome once I ditch 5″ of barrel. If you (or anyone reading) are on the fence about one of these rails do it. Even if you weren’t thinking KeyMod before. I 100% agree that “floored” is the only way to describe my impressions of this rail. I used to be a staunched supporter of Mark Larue, but this rail has made me a BCM customer.

      This guy likes it too https://www.youtube.com/watch?v=-AjlvIsCFp0 and a great detailed walkthrough of the install. If you “build” (ie assemble) AR’s you know what Tyler was talking about having to shim and or toque the snot out of barrel nuts to get a handguard to time properly. Another positive it the way the handguard tightens from the top as opposed to the bottom like typical clamp on designs which overly stress the top channel and will work loose over time. The KMR gets tighter as the barrel heats up.

      Good review, great rail!

      • ” used to be a staunched supporter of Mark Larue, but this rail has made me a BCM customer”

        STAUNCH, not Staunched.

  6. Keymod is great. Slim, light (way way way lighter than standard 1913 quad rails), comfortable to hold without gloves or rail covers. My only complaint is that the really slim ones can heat up with extended use but they have good air flow so it’s never been a serious problem.

    • +1. I tried to explain the difference between gouging/raising prices vs. caving to Bloomberg to a friend of mine but he didn’t get it. CTD didn’t just raise prices on stuff (like everyone else did), they stopped selling evil black rifles with the shoulder thingy that goes up.

  9. Its hard not sounding like an asshat saying something like this, but can anyone justify having picatinny rails across the entire top of the handguard?

    Front iron sight + strobey flashlight thing that looks like a pack of cards right behind it takes like five or six inches, max.

    Does anyone make a 360* octagon/nonagon/round/ keymod free float rail with zero installed picatinny segments? Troy does, but I don’t believe their stuff is this light.

  10. I’m hoping that just about everything now made in aluminum will be available in an aluminum-magnesium alloy in the near future. At the top of my gun build projects list is a lightweight AR-15 without compromises that combines the MAG Tactical Systems aluminum-magnesium receiver with the BCM aluminum-magnesium KMR. I hope more KMR lengths will be released soon. The BCM Gunfighter stock (7.5oz) is a must. I’m thinking a Christensen Arms carbon fiber wrapped stainless steel 1:8 twist barrel under the KMR for no compromise in performance whatsoever while still being lightweight. And a lightweight bolt carrier group, perhaps MAG Tactical’s skeletonized BCG or the Sharps Relia-Bolt system, as well as other parts.

    • Truly. I wonder at what point does the faddish uber light weight crap end? Money would be better spent on a gym if a few ounces are such a bother.

      • Lightweight once experienced is hard to ignore. It has nothing to do with lugging around a “Heavy” weapon for me. It’s faster on target, and one more piece of light weight kit that makes your life easier. I used to lug around a 70-80 lb ruck just fine in my 20’s. Then as a civilian I lugged around a 35 lb backpack for scouts and thought it was great. Then I graduated to a 8lb load (backpack, sleeping bag, tent and cooking gear, 15 lbs with 3 days food and water purifiring along the way) and every 3 to 7 day trip is like a day hike. You can enjoy the scenery while most people you pass on the trail have their head down and are trudging along. A light weight rifle is just as fun for a 50 yr old as it would be for the Rock, macho strength has nothing to do with it. If you don’t get it, you never will.

        • @Frank, sure I get it. Completely. But at some point one pays more dollars and the returns are absolutely diminishing. For the large vast majority of dudes out there, the most PT they get is walking from the parking lot to the firing line with their gut swaying the whole way. A 50 yard hump. Those are the folks I’m speaking to here.

  11. I bought a 14.5 ELW BCM upper with 13″ KMR handguard a couple months ago when BCM was having a sale on them. It’s my new favorite rifle to shoot. So light, and handles like a dream. I love that gun.

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