Basics Series: KeyMod vs M-LOK vs Picatinny – With the trend of an increase number of shooters joining the community, we feel a series of basic topics to cover the essentials for those just getting into the firearms community. For today’s topic, lets cover mounting options. So, you got a shiny new AR-15 and want to drop those plastic handguards. You literally have hundreds if not thousands of choices out there. One thing you’ll start to realize very early on is the following terms: Picatinny, KeyMod, and M-LOK. This is the initial choice you should make before narrowing the vast choices you have down. It will determine what and how you will buy accessories to mount going forward. Let’s break it each platform down.
The most familiar and longest running platform of them all. An evolution of the Weaver system and adopted my various militaries across the globe, Picatinny rails are effective and easy to utilize. It has a received a NATO designation of MIL-STD-1913 and is the go to mil-spec process of attaching accessories to a firearm. It has the largest users of any other mounting platform still to this day and for good reason – it’s simple, widely universal, and extremely versatile in the positioning of mounted accessories. Recognize it easily with its distinct horizontal slots spaced precisely to spec across the mountable portions of the handguard, with a spacing of 0.180 inches or 4.57mm.. Attaching accessories to a Picatinny rail is as easy as either clamping the add-on to an available slot where you want it and tightening the cross bolt via the thumbscrew, bolt, or QD lever. The accessory stays in place by the center cross bolt locking into the slot and the clamp keeping it tight. Another method is the accessory is slid on from the front of the rail and then locked down once you have it where you want it. This method is common on pistol accessories.
There are a few downsides to this system to keep in mind. The biggest problem is that majority of those Picatinny slots…. are not – and will not ever be used. This results in additional bulk and weight that will make your nimble carbine front heavy and there is nothing I hate more than a grossly unbalanced rifle. The diameter of the handguard will also be noticeably larger than its competitor since there has to be rail on all mounting faces which results in the final complaint: sharp rectangles are not comfortable. If not using any type of foregrip, the slots will cut and dig into your hands, but don’t get me wrong, it’s nothing terrible and it’ll give you some additional grip. All full Picatinny rails will have a blocky feel to them verses their more ergonomic alternatives.
Final thoughts on Picatinny Rails – If the blocky feel and additional weight/bulk of the Picatinny platform doesn’t bother you then there is nothing wrong with this tried and true design. Enjoy almost guaranteed mounting for any accessory without any additional parts or expense. With the endless offerings of this system, you can probably find the cheapest rails in this format.
Noveske, the specialists in high-end AR systems, invented this replacement for the mil-spec Picatinny rail. It gets its name from the key-shaped mounting holes and its ability to be modular. “KeyMod uses “Negative Space” mounting where accessories attach directly to the handguard, instead of relying on an intermediary interface like Picatinny’s rail slots.. Add Picatinny rail strips to a KeyMod rail to use Picatinny accessories, which still dominate the market. The biggest advantage to this system is that you only add rails or accessories on where you want them. You aren’t stuck with a large amount of space unused thus saving weight and improving ergonomics of the handguard. Attaching an accessory to a KeyMod rail is as follows: The accessory or rail strip possesses a specialized keyed nut and a larger diameter shoe that is loosely attached to the rail or attachment. Drop the larger diameter shoe into the larger hole section of the KeyMod handguard and push it forward. Once pushed forward, the screw is then torqued down so it pulls the shoe towards the rail or attachment and is clamped into place. In the end, you’ll have rail sections or direct mount gun accessories where you want them. KeyMod rails can be more versatile compared to Picatinny as well depending on which one you go with, for example with Picatinny, you can only mount at the 12, 3, 6, and 9 o’clock positions. With certain KeyMod rails, they have the option of mounting at 45-degree points or 2, 5, 8, and 11 o’clock positions.
There are very few downsides to KeyMod but one that sticks out in a lot people’s mind is the direction in which it’s in the locked position. The rail or accessories is pushed forward then locked down, the concern is if pulled back hard enough, like a foregrip, it can dis-engage. There have been arguments that the key holes should face the other way so you are pulling TOWARDS the locked position, not away. I have personally never experience this happening but I can see how it’s possible. A minor complaint that some people have is that the keyhole shaped cut-outs have two sharp points and if you have fleshy hands, your skin may squeeze into the keyhole cutouts and can become painful. Again, not a complaint that I personally have had but it’s out there.
Final Thoughts on KeyMod Handguards – If looking for a slim handguard that’s modular with a large following of adaptation, then there is no reason not to go for one. The actual shape of the KeyMod cutout has a secondary advantage of being able to mount QD slings directly to any of the slots – IF the rail is not too thick and matches the 3/8” diameter QD. If you love to really, REALLY tuck that stock into your shoulder and hulk pull on your foregrip back or you like to use a barricade braces, then look into Picatinny or the next style – M-LOK.
(Modular Lock) – Invented by Magpul, who holds a high standard on quality components, and designed to be an improved alternative to KeyMod. It’s the next evolution of their MOE mounting system and uses the same negative space principal of the KeyMod system. Advantages of the MLOK system are pretty much the same as KeyMod – Slim profile, attach accessories or rails to only where you want them, ability to mount 45-degree positions on some rails, and light weight. The difference (and maybe advantage) is the way rails and accessories mount. MLOK rails use rectangular holes vice keyhole shaped cutouts. Attach a rectangular shoe to the rail or accessory with a screw, then drop it into one of the MLOK cutouts of your choice and tighten the screw. When you start tightening, the shoe engages at 90 degrees and locks into place. Since MLOK can be engaged and locked in either the forward or rearward position of the MLOK cutout, it does not have the potential issue that KeyMod has and disengaged if pulled hard enough opposite of it’s locked position. If mounting a grip, mount it in the rear position – if mounting a light, then feel free to mount it in the forward position since you are pushing forward to engage a button. MLOK handguards also feel better in the hand if held bare without any attachments. The chamfered rectangular cutouts prevent cutting or digging into your skin, unlike Picatinny or KeyMod. This results a very smooth and slim handguard to hold on to if not using a foregrip or angled foregrip.
Final Thoughts on M-LOK Handguards – MLOK is my personal go to choice for a mounting platform. I typically only mount a light, front sight, and maybe a foregrip, the rest of the time, I prefer to just hold on to the handguard. The smooth snag free finish of the MLOK is a very ergonomic choice and is just as versatile as the other choices with the exception of having to mount a QD attachment for a sling vs the built in QD capability of KeyMod. The number of MLOK compatible direct mount accessories is growing everyday and you can always get rail strips to mount common Picatinny accessories. If you’re a Magpul fan then MLOK is the way to go as it’s their technology so they will base their future products on it. If you have invested in older MOE accessories, Magpul makes an adapter plate that will allow the use of those accessories on MLOK rails. Their basic polymer handguards now contain MLOK slots so if all you want is a basic low-cost handguard with some options, their handguards will be a great choice.
Basics Series: KeyMod vs M-LOK vs Picatinny