With no less than three rail integration systems on the market for rifle platforms, it can be dizzying to figure out the pros and cons of each but don’t worry, we are here to break it all down to help you make an informed choice.
While the AR-15 and its cousins were a design product of the late 1950s and the carrying handle/rail, with the ability to change rear sights or easily accommodate Colt’s 4x fixed optic, was revolutionary when compared to the wooden-stocked battle rifles of the past, over the last 30 years the addition of rail systems to the platform have revolutionized it beyond what Eugene Stoner originally had on the drawing board. With that in mind, let us look at the first, and oldest contestant in the fight
With that in mind, let us look at the first, and oldest contestant in the fight.
Scope maker Bill Weaver came up with his eponymous system of parallel rails and slots in the 1950s and the “Weaver base” became one of the most popular mounts for optics rings in the commercial hunting and target shooting market on the planet. However, this system, especially when lacking a locking bar in its earlier versions, was prone to canting or misalignment from scope twist during the mounting process or when ring screws backed out though it is still marketed today. With that in mind, the Weaver system grew into a military-standard (MIL-STD-1913) after strict tolerances were established by the Army’s Picatinny Arsenal in 1995. Since then, the “Picatinny rail” has been adopted widely for military service with the follow-on NATO Accessory Rail (NAR), which uses a slightly different but generally backwardly compatible rail grabber interface, now the preferred system.
All this is to say that the good ole’ “Pic rail” has been around in one form or another under a slew of names for a long time. It is still in many ways the industry standard, especially for scope and optics top rails both on factory and custom AR systems. But, it has some drawbacks when used as an accessory rail for lights, foregrips, lasers and other systems as it has sharp edges that do not contribute to being easy on the palms and the additional weight of long monobloc rails on a rifle’s handguard can add to a muzzle-heavy imbalance, especially considering today’s lighter skeletonized or polymer receivers– though this can be mitigated with polymer rails to trim weight down and rail covers can help keep it from catching on skin and fabric.
This leads us to the new kids on the block.
Then-Colorado-based Magpul in 2007 came up with a rail system for their Masada vaporware rifle concept they called the “MOE slot” which they began to market actively a few years later. This horizontal 20mm long slot system grew up to become the freely licensed M-LOK by 2014, using twin T-slot nuts to attach accessories ranging from vert grips and hand stops to lights, bipod mounts, sling mounts and tape switches. When coupled with a polymer MOE handguard, you can save weight while having lots of options for added gear to add that weight right back in!
Since the slots weigh nothing, unlike with Pic rails, having dozens of them on a handguard does not add empty ounces to a weapon and allows the user to move accessories almost anywhere.
The system has become very popular and is well-regarded in professional circles, with the U.S Special Operations Command recently adopting M-LOK as the standard for several of their small arms programs after testing by the Navy found that it’s performance results– including MOA consistency as well as drop and load testing– surpassed those achieved by other modular rail systems.
Designed by Eric Kincel at VLTOR in 2011, the open-source (as opposed to licensed as with M-Lok) KeyMod system takes its name from its distinctive key-hole shape and resembles modular workshop shelving to a degree. The interface uses a slot-and-nut system and, like M-Lok, uses the same spacing arrangement as legacy Pic rails to keep things simple. As KeyMod is open to the public, there have been several minor tweaks to the design unique to manufacturers that are all still backward compatible to one degree or another. As the KeyMod design allows for a very tight attachment– if torqued to spec– some prefer it to the similar M-Lok when mounting/remounting optics, and of course, you can always add Pic to it. This is augmented by the fact the “keyhole” on the rail is to the rear, meaning recoil will only help tighten the mount rather than loosen it.
Besides VLTOR, Accuracy International and Bravo Company are big into KeyMod, while M-Lok is seen on Magpul’s lines and those who use their MOE accessories in their builds.
So, which is the best?
Well, it’s like asking which is better between Dodge, GM, and Ford– fans of each will debate their own personal experience to the desired outcome and each have their place. Magpul’s system, though the newest to the market, has a big bump from the recent special operations adoption yet KeyMod does everything Magpul can do and is open-source, while Pic is so widespread you can and will continue to find it everywhere for decades– and indeed, Pic rails sections are often used with the other two.
In the end, the top rail is owned by Picatinny, especially when it comes to optics. As for the fight between KeyMod and M-LOK, the latter is easier to machine and is widely seen as outselling the former, which means on a long enough timeline you will likely continue to see more M-LOK moving forward.
Your mileage, of course, may vary.