AR Handguards: KeyMod Vs. M-LOK

If you’ve been looking to build or upgrade an AR, between KeyMod vs. M-LOK handguards, which is right for you?

If you don’t want to use quad rails or a traditional handguard on that next AR build (or if you’re looking to put more modern furniture on your current rifle), your two options are either KeyMod or M-LOK. 

Is one generally better than the other? Do either offer any niche advantages? What are the best handguard models for each style?

What Are KeyMod And M-LOK? 

KeyMod and M-LOK were both invented to mount various accessories to an AR-style rifle without the bulk and weight of a quad rail “cheese grater” handguard. 

Besides offering more attachment points for accessories, both styles of handguards often provide another key advantage: free-floating. Because most M-LOK and KeyMod handguard models attach to the barrel nut rather than the barrel itself, they improve a rifle’s potential for mechanical accuracy. This is opposed to traditional handguards that also attach to the barrel, meaning that force imparted on the handguard can transfer to the barrel and affect the point of impact. Because of this, some people opt to run a KeyMod or M-LOK handguard not because they want to attach any specific accessories but because they just want their barrel to be free-floated.

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While free-floating has undoubtedly become the more popular and available style, be aware that not all M-LOK or KeyMod handguards are free-floated. Some of the less expensive and simpler handguards that feature these attachment systems are still installed the traditional way.

Who Created KeyMod And M-LOK? 

Both rail systems started life in the private sector before eventually becoming noticed and subsequently adopted by various armed organizations around the globe.

While M-LOK technically came first, the design we know today is predated by KeyMod. Designed by VLTOR Weapon Systems, KeyMod was released by Noveske Rifleworks in 2012 and then published as an open-source design so it could be utilized freely by the rest of the industry. The name comes from the design’s distinct keyhole-shaped slots.

M-LOK (Modular Lock) was invented by Magpul Industries, with the proto-M-LOK design emerging as the MOE handguard in 2007. 

The original MOE system used a series of slots (much like M-LOK) but had the drawback of requiring the user to install a T-nut behind the handguard. Doing so required either taking the handguard off every time you wanted to mount something or trying to find a way to drop it in place. 

The limitations were obvious, so Magpul released a revised scheme in 2014 which is what we know as M-LOK today. M-LOK is still owned by Magpul Industries, but it allows other companies to use it as a sort of “conditional free license” rather than a true open-source design. 

How Do They Work?

In the cases of both rail systems, the magic has less to do with the handguards themselves and more with the mounting systems integrated into them. Both KeyMod and M-LOK use negative space (i.e., holes) for attaching accessories, and because you’re putting the mounting hardware into rather than onto the handguard (as with Picatinny), it allows for a sleeker and more streamlined design.

As for KeyMod, the attachment is a flared bolt that goes into the big hole and slides forward into the little hole. The user then tightens the bolt to secure it and attach whatever accessory they were trying to install. Typically, KeyMod accessories will occupy at least two holes for the most secure attachment. 

M-LOK uses a series of rectangular slots. Attachments have T-nuts that are rotated parallel to the slot, inserted, then tightened to turn the T-nuts perpendicular to the rail slot, locking it in place. 

In the broad strokes, KeyMod is a little more user-friendly and intuitive to use, but not so much that it makes a huge difference. 

Does The Military Use M-LOK Or KeyMod? What Are The Pros & Cons? 

When the U.S. military is using something besides Picatinny rails, it uses M-LOK. Testing by the Crane Division of the Naval Surface Warfare Center revealed it was the superior system in some respects, so it was selected for use by USSOCOM. 

Rails selected for use by various groups in the U.S. military include the Geissele Super HK rail and Geissele Super Modular Rail. The new Sig Sauer M5 rifle, of course, uses an M-LOK handguard as well. 

Testing by Crane compared three different handguards offered with both M-LOK and KeyMod slots from Aero Precision, Midwest Industries and Seekins Precision. While no handguards suffered any failures withstanding recoil, stress testing found that KeyMod was the most fragile of the bunch.

KeyMod handguards suffered more failures in drop testing and load testing, with the common failure being a stress fracture between slots. Usually, the mounting bolt would crack the handguard. Several handguards also came free of the barrel nut in drop tests. 

Part of the testing included zeroing an IR laser, taking the unit off the handguard, then reinstalling and checking for POA (Point of Aim) shift, with the idea being to establish which mounting system will hold zero better. Again, M-LOK emerged as the clear winner.

So…what does this mean for the pros and cons? 

For the typical user, they won’t notice any appreciable difference.

Most people aren’t repeatedly dropping their rifles on concrete or using an IR laser aiming device. KeyMod only failed in Crane’s testing when subjected to abuse far beyond what the typical civilian owner will ever subject their rifle to. 

The much more noticeable drawback in the current year is the availability of compatible accessories. M-LOK has established itself as the more popular option of the two, meaning that most accessories today are offered primarily with M-LOK or Picatinny mounting hardware. There’s plenty of KeyMod-compatible stuff too, just not quite as much. The continued availability of KeyMod accessories is probably helped by the system’s higher popularity in Europe.

KeyMod Vs. M-LOK: Which Is Best For You?

As mentioned, military testing revealed that the two shortcomings of KeyMod in comparison to M-LOK are durability and its ability to retain zero with laser aiming devices.

This means that for most people in most situations, KeyMod will work just fine. If, however, you’re someone who wants to run your rifle with night vision and/or make it as bomb-proof as possible, an M-LOK handguard will be the better choice. If you plan on using an IR laser, just ensure that the handguard model you choose has a good track record for maintaining zero.

The 6 Best M-LOK And KeyMod Handguards

M-LOK

Geissele Super Modular Rail MK4 

Geissele was one of the first companies to design an M-LOK rail with the use of a night vision sighting system (and therefore the need to minimize rail flex to preserve zero) as a priority. The Super Modular Rails are free-floated and made to mount a PEQ-15, MAWL or similar device at the forward end of the handguard. 

Geissele Super Modular Rails are a buy-once, cry-once item, with MSRP ranging between $275 and $350 depending on the length and finish selected. 

Aero Industries Quantum M-LOK Handguards 

Aero Industries’ Quantum M-LOK handguards are a fantastic middle-ground free-floated M-LOK handguard option. They’re durable enough to survive what most users will put them through and can securely mount accessories.

These handguards feature some Picatinny rail on top with M-LOK slots at 3, 6, and 9 o’clock and QD slots at the rear of the handguard. There are multiple lengths and finishes available and MSRP starts at $110, but they can be found for under $90 with some hunting. 

Magpul MOE M-LOK Handgaurd 

Want to add a bit of M-LOK to your budget-friendly M4 clone? The go-to handguard is (and has been for some time) Magpul MOE handguards. These two-piece handguards drop in on any rifle with a front sight block (circular or triangular handguard caps both work) and a D-ring. They are durable, functional, and cheap. The tradeoff to the simplicity and low price is that these are not free-floated.

These are available for carbine, mid-length and rifle-length gas systems and feature M-LOK slots at 3, 6 and 9 o’clock. You can choose between black, FDE, grey and OD green colors and they can easily be found for less than $40. 

KeyMod

Bravo Company KMR Alpha 

The KMR Alpha is a free-floating, fully-railed aluminum handguard with KeyMod slots at 3, 6, and 9 o’clock. They’re available in either black or FDE and come in lengths ranging from 7 to 17 inches. Bravo Company is one of the better manufacturers of AR-pattern rifles and accessories, so this is about as good as it gets for a KeyMod handguard. 

MSRP varies by length, starting at $180 for the 7- and 8-inch rails and topping out at $235 for the 17-inch, but you can usually find them for much cheaper through third-party retailers. 

Leapers UTG Super Slim KeyMod Handguard

Only offered in 15- and 17-inch lengths (15-inch for AR-15 and Ruger Precision Rifles, 17-inch for select AR-10 variants) the Leapers UTG SuperSlim is a good mid-tier offering to get someone a decent free-floated KeyMod handguard without busting the bank. 

A fully railed top with KeyMod slots at 3, 6, 9, 10, 2, 8 and 5 o’clock, it features a slim profile for low-profile gas blocks and built-in anti-rotation tabs for secure mounting. MSRP is $140, but they can usually be found for around $100 through third-party retailers. 

Bravo Company PKMR 

The PKMR (Polymer KeyMod Rail) is the KeyMod equivalent of Magpul’s MOE handguard. They’re available in FDE or black and are offered for carbine (round end cap only) or mid-length (triangle end cap only) gas system rifles. MSRP is $40 but they can usually be found for around half that price, making these a great option for someone who just wants a cheap way to add some accessories to their rifle’s handguard.

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