This was originally published on a blog I wrote back in March of 2017, but I’ve added a few things at the end to include the SOCOM testing that really marked the rise of M-LOK.
So, I see the question: “Which is better, KeyMod or M-LOK?” You’ll see lots of opinions on either side, but I thought I’d give my observations that led me to adopt M-LOK. I’ve seen some debates that center around the brand loyalty and market share, but I think it’s fairly safe to say that both the VLTOR/Noveske team and Magpul have been around long enough to last in a marketing-only competition, so I’ll disregard that for my purposes.
First off, a bit of background. KeyMod actually came first in 2012. KeyMod is completely open-source. You can literally find the technical drawings on Wikipedia. There is no fee, and no license to utilize KeyMod. Magpul developed the M-LOK system as an offshoot of its MOE attachment system when they found that the KeyMod system didn’t work well with polymer handguards (which, of course, Magpul specialized in). M-LOK is a licensed system, but it is free. Magpul requires users to sign a licensing agreement and submit their designs to Magpul for their approval. Technical drawings are not available until the license is signed.
So why did I choose M-LOK?
1. The design of KeyMod involves machining the rail at angles on the interior of the rail. Because of this, the rail actually gets thinner the closer it gets to the exterior of the rail. The minimum thickness of the rail is .080″, but that is at the thickest point. The thinnest point on the key is only .026″ (plus or minus .005″). That is the issue Magpul had with KeyMod – the thinner polymer at the outside was breaking. I only have anecdotal evidence of this happening with aluminum handguards, but I still prefer the uniform thickness of M-LOK, which is a minimum of .080″.
2. The M-LOK design provides more area in contact and is arguably stronger overall. The Magpul t-nut provides ~.080″ of purchase on each side of the screw shaft. The KeyMod nut provides ~.045″ on each side. Now, the KeyMod nut fits into the angle of the key (eg., the head of the nut tapers into the shaft, as opposed to a hard 90 degree angle). Theoretically, this should provide more holding power than a standard T of the same size, but once again, the rail is only .026″ thick at its thinnest point. I’ll take a standard of .080″ thick with .080″ of grabbing power on each side.
3. KeyMod accessories require an additional point of contact for attachment. Because KeyMod slides into the keys to lock, without an additional point of contact (i.e., two points of contact for a one nut attachment, three points of contact for a two nut attachment, and so on), the KeyMod accessory will literally slide backwards and out of the key slot. This is not an issue with M-LOK. While an accessory with only one t-nut will require a second point of contact (rare, but they exist), any accessory of two t-nuts or more should be good to go without any additional points of contact (although for accessories spanning more than one slot, additional points of contact will prevent slippage). Requiring additional points of contact introduces more chances of failure (in my opinion). These additional points of contact also tend to make the accessories larger, meaning they can end up heavier and take up more rail space. This is because many designers add their additional point on either the front or back of the accessory. Several designers have made their accessories more streamlined and added the additional point between the nuts, and thus maintaining the the same size while still keeping the additional point of contact, but that doesn’t negate the fact that KeyMod will fail without the correctly machined and positioned additional points. For the occasional M-LOK accessory that needs an extra point of contact, almost all are found between the two t-nuts.
4. Magpul’s requirement of a license means standardization. Yeah, I know, most people hate the word standardization, but it’s not always bad. Because of the licensing requirement, you are assured by Magpul that any piece of gear bearing the M-LOK logo (assuming someone didn’t just throw it on there) should be compatible with any other piece of M-LOK gear. While KeyMod is technically a standard design, anyone is realistically free to change it up, and there is no higher authority assuring compatibility. You’ll just have to see if it works, or read about it on the internet.
There are some other points, but they are mostly at the manufacturer level, and would most likely not affect an end user purchase. I’ve also personally found M-LOK to be easier to install than my KeyMod parts, mostly due to the additional lug required. I’m currently in the process of changing out to solely M-LOK.
UPDATES: Since I wrote that original blog post, US Special Operations Command tasked Naval Surface Warfare Center – Crane with conducting an evaluation of KeyMod versus M-LOK. M-LOK outperformed KeyMod in every test, including drop testing, return to zero, and attachment strength. If you’d like to see the full results, Soldier Systems Daily supplied a link here.
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