Which one and why? A little worried about the strength of the BCM KMR due to its super light weight.
- Thread starter mckelveymx
- Start date
Two super advanced designs, no doubt.
The KMR is definitely lighter. Its designer is a materials application expert of the highest order, so I would not be worried about the strength. But, like the Noveske NSR, it's skinny. So, it's going to get hotter. But, in the race to be the lightest and a still useful forend, it's going to be impossible to beat. Even the two add-on rails that come with it are super-light polymer. I just built one up:
For a carbine class on a warm day, shooting 500+ rounds, I'd prefer the roomier Geissele at an extra few ounces. Remember, it has rails and sling swivel mounts integral to the design, already. At under 13 ounces, it is hardly what you would call heavy!
Both forends come with clear, well written instructions, as well as a special tool for the respective barrel nut installation.
The KMR is definitely lighter. Its designer is a materials application expert of the highest order, so I would not be worried about the strength. But, like the Noveske NSR, it's skinny. So, it's going to get hotter. But, in the race to be the lightest and a still useful forend, it's going to be impossible to beat. Even the two add-on rails that come with it are super-light polymer. I just built one up:
For a carbine class on a warm day, shooting 500+ rounds, I'd prefer the roomier Geissele at an extra few ounces. Remember, it has rails and sling swivel mounts integral to the design, already. At under 13 ounces, it is hardly what you would call heavy!
Both forends come with clear, well written instructions, as well as a special tool for the respective barrel nut installation.
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Here are two reviews of the BCM KMR . IMHO, the Geissele SMR and BCM KMR are currently the state of the art. Just pick your preference. http://progunfighter.com/bcm-keymod-modular-rail-system-kmr/
Bravo Company KMR Handguard! Lightweight KeyMod Innovation - YouTube
Bravo Company KMR Handguard! Lightweight KeyMod Innovation - YouTube
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The 15" KMRs have been available - but sold-out last I checked.
Last week I purchased a 16" BCM SS410 upper with a 15" KMR rail (pairing it with a NF 2.25-10x42). Incredibly light rails.
You may be able to get a 15" KMR with a complete upper from BCM - just not separately at the moment.
**BONUS - BCM is offering free BCM BCG with new uppers at the moment - a good time to buy!
Last week I purchased a 16" BCM SS410 upper with a 15" KMR rail (pairing it with a NF 2.25-10x42). Incredibly light rails.
You may be able to get a 15" KMR with a complete upper from BCM - just not separately at the moment.
**BONUS - BCM is offering free BCM BCG with new uppers at the moment - a good time to buy!
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I would take the KMR over the Geissele for 2 reasons. One would be the additional mounting surfaces with BCM's 7-sided keymod design. The other would be the slimmer outside diameter. That 1.5"-1.7" OD is just about a perfect fit for my hands. While the Geissele's inside diameter is 1.3"-ish, the OD is over 2". I'm also using keymod to reduce unnecessary weight and with direct attach keymod accessories starting to come out there won't be any need for additional pic rails.
IMHO, the strength issue with the KMR hasn't produced any negative effects (I can physically flex the 13" KMR about 1/8" in any direction when installed). It does heat up faster than any other handguard I've used, but I think that has to do with the material used and the thickness of the walls of the handguard. They're comparatively a little more than half as thick as others.
At the end of the day, the KAC URX 4 proved to be the best of both worlds based on my preferences. It gives you the same number of options in regards to mounting interfaces, extremely solid lock up and very high strength, integrated sling mounting options, relatively light (12.3 oz), 1.55" ID and OD is only 1.7", and I've never been able to feel any excessive heat through the URX 4. It's a little cheaper than the Geissele but comes out to about the same if you're needing picatinny rails.
IMHO, the strength issue with the KMR hasn't produced any negative effects (I can physically flex the 13" KMR about 1/8" in any direction when installed). It does heat up faster than any other handguard I've used, but I think that has to do with the material used and the thickness of the walls of the handguard. They're comparatively a little more than half as thick as others.
At the end of the day, the KAC URX 4 proved to be the best of both worlds based on my preferences. It gives you the same number of options in regards to mounting interfaces, extremely solid lock up and very high strength, integrated sling mounting options, relatively light (12.3 oz), 1.55" ID and OD is only 1.7", and I've never been able to feel any excessive heat through the URX 4. It's a little cheaper than the Geissele but comes out to about the same if you're needing picatinny rails.
You can get movement between the barrel and the opening in the end of the forend with just what I would call medium hand pressure. But, is it the handguard moving, or the barrel?
It's the barrel more than the handguard, or more specifically the junction of the barrel and upper receiver.
Don't believe me? Take an AR' upper with no sights and invert it onto its top rail on a smooth, hard surface. Now, push down on the barrel - It moves. It's not the handguard flexing, because the handguard is completely supported by the hard surface. There may be some minuscule flex in the barrel itself under such light pressure, but really it's the barrel/receiver junction flexing.
On the Magpul Precision Rifle video series, there is an ultra slow motion film clip of Costa banging away with a suppressed Larue .308 PredatAR, the model with the light profile barrel. I watched that clip over and over in complete fascination. The "noodling" of the barrel, the forend, the entire upper receiver simply had to be seen to be believed!
I'll have to take a look at that video. But, MSTN, what you described as "medium hand pressure" being able to very noticeably move the handguard at the furthest point at the muzzle end is right on. It's hard to really describe in the same context as noting the high quality of the handguard as well.
When I finished the first build with a KMR I was initially concerned with barrel movement. I threw the upper in a vice, but in a laser bore sight aimed at a target in the shop (was only 31 yds away) and began applying moderate pressure in different directions to see if my bore was moving. At 31 yds I didn't see any movement, BUT that may have not been the case at longer ranges - even 100 yds. Nevertheless, you've got me curious now. I'm going to run the same test and see if I get any measureable movement at 100 & 200 at the range tomorrow. I'll have to put a camera at the target to make sure I'm able to review, but this should definitely be interesting...
When I finished the first build with a KMR I was initially concerned with barrel movement. I threw the upper in a vice, but in a laser bore sight aimed at a target in the shop (was only 31 yds away) and began applying moderate pressure in different directions to see if my bore was moving. At 31 yds I didn't see any movement, BUT that may have not been the case at longer ranges - even 100 yds. Nevertheless, you've got me curious now. I'm going to run the same test and see if I get any measureable movement at 100 & 200 at the range tomorrow. I'll have to put a camera at the target to make sure I'm able to review, but this should definitely be interesting...
I'm running a KMR on my recce that I used at the PNTC two-day DMR match yesterday and today and it was rock solid all weekend while bracing it against trees, slinging up, and running it off the bipod.
Installation was quite easy, I love the reduced weight, the KMR-13 is half the weight of the LaRue 11.0 that it replaced, and I'd say just as solid plus it has an additional 2 inches of up front to help get my bipod out farther while still giving my arm room to get at full extension. The reduced weight helped offset the heavier WOA barrel I had put on there and really balanced out the gun nicely. I can't comment on how hot the handguard gets after extended firing but I had no issues with hit over the course of the match when it set out in the sun, had rounds run through it in pretty quick fashion, and had it sit out in the sun some more. It's going to be hard to top the KMR in my opinion and I'm going to look at getting another one for my other AR.
Installation was quite easy, I love the reduced weight, the KMR-13 is half the weight of the LaRue 11.0 that it replaced, and I'd say just as solid plus it has an additional 2 inches of up front to help get my bipod out farther while still giving my arm room to get at full extension. The reduced weight helped offset the heavier WOA barrel I had put on there and really balanced out the gun nicely. I can't comment on how hot the handguard gets after extended firing but I had no issues with hit over the course of the match when it set out in the sun, had rounds run through it in pretty quick fashion, and had it sit out in the sun some more. It's going to be hard to top the KMR in my opinion and I'm going to look at getting another one for my other AR.
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