BCM KMR KeyMod Rail Review

[plouffedaddy]

I've had the KMR for about a month now and here's what I've found:

Pros:
-Very strong design. The indexed cross bolt and barrel nut system (shown in the video) is a very solid design
-Lightweight. Aluminum/magnesium blend results in a 13'' rail that weights 7.7oz (with mounting hardware)
-Material dissipates heat well. See the rapid fire portion of the video for actual thermometer numbers on that one.
-KeyMod mounting points at traditional 3, 6, and 9 o'clock positions. Also, offset KeyMod attachment points that allow more mounting options.
-Comes with a 5 and 7 slot KeyMod rail sections.
-No indexing required for the barrel nut.
-Available in 10 & 13'' lengths. 9'' and 15'' models are coming as are direct KeyMod accessories.

Cons:
-The only one folks bring up is the finish durability. I personally think the finish looks pretty good but I suppose that's in the eye of the beholder….

Here's a video of some shooting, a discussion of the features of the rail, and my overall impressions of it:

 

[119er]

One of these is on the list for my 18" "SPR" build. Not sure whether to go with the 13" or 15". Thanks for your input.

 

[9mmepiphany]

I've been very happy with mine.



Just waiting for them to offer more KeyMod accessories...the forward grip they showed off at SHOT looked like a must have

 

[plouffedaddy]

Just waiting for them to offer more KeyMod accessories...the forward grip they showed off at SHOT looked like a must have

Ditto.

 

[taliv]

have either of you beat them up much? they dent easily? or crack/break?

 

[9mmepiphany]

If they do I haven't noticed...I'm not exactly graceful, but I now understand why you don't leave them leaning against things.

From what I've read, the complaint is that the finish wears when you attach and removed accessories...well, duh. It isn't like the alloy is going to rust

I didn't really notice until I read about it. I figure it will hide the little oopsies from when I built the lower

 

[MCMXI]

On their website BCM says of the KMR ...

"Manufactured from an exclusive blended aluminum and magnesium alloy, the BCM KMR weighs 30-40% less than pure aluminum with the same strength properties."

By "pure aluminum" they must mean an aluminum alloy since pure aluminium is very soft, but which alloy? Aluminum alloys have very different mechanical properties.

 

[fletcher]

By "pure aluminum" they must mean an aluminum alloy since pure aluminium is very soft, but which alloy? Aluminum alloys have very different mechanical properties.

It looks like they mean it is an Al-Mg alloy, although based on the density it must be considered a magnesium alloy (vast majority Mg).

 

[MCMXI]

My first thought was that it's a 5000 series aluminum alloy since they have the highest Mg content in the 3% to 5% range but they're not "exclusive". It would be interesting to know more about the alloy and what other applications it's used for.

 

[fletcher]

Magnesium alloys like AZ31B, AZ61A, WE43C, and ZK60A would likely be pretty close to whatever they're using with regards to strength, density, etc. Because of high strength-to-weight, they tend to be used to squeeze weight out of parts/assemblies. Engine valve covers, gearbox castings, wheels, etc. are common applications.

 

[plouffedaddy]

I didn't really notice until I read about it.

Ditto. I read about it on the inter webs and then looked to see if it was true.

 

[henschman]

Cool... I am all for lighter weight. I am working on a lightweight carbine build now, but it doesn't look like they yet make this handguard in the length I need for my middy gas system (9"). I will probably end up going with the MI-SS Gen 2, which I have on my 20" and love. It is hard to imagine a handguard being any lighter than that MI, but if BCM pulled it off, more power to them.

 

[9mmepiphany]

They are currently available in 10" and 13"; the 9" and 15" should be available this summer.

The 13" one on my rifle weighs 5.5oz. the mounting hardware adds 2.2oz for a total of 7.7oz. The MI-SS Gen 2, 9" one weighs 8.3oz

 

[ZGunner]

The 13" one on my rifle weighs 5.5oz. the mounting hardware adds 2.2oz for a total of 7.7oz. The MI-SS Gen 2, 9" one weighs 8.3oz

So the 9" KMR rail should weigh in right at 6 oz with mounting hardware? That is ridiculously light. I now have the urge to build an ultralight AR just to see how light it can really be.

 

[Centurian22]

For my first build I'm debating between this rail and the Samson Evolution Keymod 15" ($205 vs $270) less than 6oz more weight and I really like the look of the 15" on a 16" barrel. I'll be interested to see the price and weight of the KMR 15. The Evo Keymod has keymod at 3, 6, and 9 but has their own backer plate mounting at 16 different indexes around the clock, and mounts to the standard barrel nut with shims and a 'bottom clamp' design. I like BCM KMR's mounting a little better, seems like it might be more solid.

 

[9mmepiphany]

less than 6oz more weight

It might not sound like much, but consider that it doubles the weight of the 13" KMR.

I have to admit that was didn't even know how nice the barrel nut attachment of the KMR was until after I made my purchase, since I got it as a complete upper