Today we’re talking about Keymod and M-LOK. They have a couple names: handguards or rails.  But did you know that there are six types of rail systems out there for your favorite guns? There is the Dovetail rail, Weaver rail, Warsaw Pact rail, Picatinny rail, Keymod and the M-Lok. For the past decade, Keymod and M-LOK have been the most used and most popular options on the market. But which one is the better rail system? You can only choose one for your rifle, so let’s weigh the pros and cons of each to determine which is the winner. 

Keymod vs Mlok History 

KeyMod began in 2012 as a combined effort from the experts at VLTOR and Noveske. VLTOR is known for manufacturing and selling innovative weapon system accessories. Noveske has been known to produce high quality competition grade rifle barrels that have also been used by the military. They also make high end custom rifles that are quite expensive.  

M-LOK’s origins come from the 2007 concept rifle that Magpul helped design, the Masada. You’ve probably seen it in some movies and video games but today we know it as the Bushmaster ACR. Masada’s initial design had an interesting handguard with three slots on the left and right sides of the handguard. Those slots lived on to help refine Magpul’s line of MOE rail-compatible products. Its result was the Modular Lock System, or M-LOK for short.

No critical comparison of these two rail systems would be complete without mentioning the tests that were conducted by the US Naval Surface Warfare Center – Crane Division, which provides Naval Support Activity via “acquisition engineering, in-service engineering and technical support for sensors, electronics, electronic warfare and special warfare weapons.” 

Crane released a comprehensive report comparing the keymod and m-lok modular rail systems. A total of 18 handguards were used to conduct the testing at Crane. 9 keymod rails tested were from Aero Precision, Midwest Industries, and Seekins. Another 9 mlok rails tested were also from the same companies (three per handguard type). The most significant results presented themselves during repeatability testing. Keymod’s point of aim shift averaged 4.9 MOA. M-lok’s point of aim shift averaged only 1.3 MOA. After the drop tests it solidified that keymod slots would not be able to hold up to the military’s desired standards as there were cracked slots and accessories falling off when dropped. If you want to learn more about the testing that was conducted you can see the full m-lok vs keymod Crane report here. 

KeyMod Overview

KeyMod allowed all other firearm manufacturers to create rails based on the same design without needing to pay for any extra rights to do so by releasing their KeyMod Tech Data Package as an open source to the public. The idea behind this was to create standardized modularity, like the picatinny rail, for which engineers could use for free. Because of these public partnerships within the 2A industry and community, we’ve certainly witnessed firsthand a boom in the firearm rail industry — a logical benefit to just about every modern day gun owner.

KeyMod Pros

So why do so many people love the KeyMod system? To start, KeyMod rails are incredibly light. When the slightest weight change can affect your aim and stamina, every ounce counts. Its slim rail offers people the opportunity to really have a fantastic grip on the handguard with their support hand which is why recently seen a lot of race guns built out with keymod. Furthermore, the KeyMod is compatible with a wide range of accessories and does not lose out on any ability to mount desired optics, sights, or ergonomic grips. Buyers get full customization ability with this rail as it doesn’t lose out the traditional picatinny quad rail at all. 

Picture the door chain on your home’s front door. The large hole accepts the locking mechanism as you slide it into the smaller section. That’s similar to how the KeyMod rail works. However in this case, you’re not as reliant on a more substantial object fitting into that smaller hole. That would be detrimental to performance if that were true. Instead, once you insert a keymod accessory or accessory rail, all you have to do is turn and tighten the lug screw accordingly and make sure the accessory bracket is secured in place. It is a very fast, safe and secure locking method.

KeyMod Cons

Small and minor parts used to lock keymod accessories down can be easy to lose and difficult to replace if you misplace them so that is definitely inconvenient. But perhaps the most concerning con… With the extreme lightweight features of the keymod handguards, there were bound to be some flaws. During drop testing, accessory rails and the keymod accessories attached to them would often separate from the handguard. The rail is smaller than most designs so if the locking nuts fall off it can be a pain to reattach them too. What’s worse is that when the keymod handguards were dropped there would likely be fractures or breaks in the keymod slots. 

M-LOK Overview

You’ve probably heard of the company Magpul at some point in your online gun research sessions. There’s a good reason for that as they’re the number one name in manufacturing firearm accessories and components. When VLTOR and Noveske were developing their KeyMod system, Magpul took note. Only two years after the KeyMod was released, Magpul developed and released their own version of a new handguard — the M-LOK system. 

M-LOK Pros

Similar to the KeyMod rail, the M-LOK is a modular accessory mounting system for rifles that comes in an attractive package in appearance and in features. The M-LOK looks fantastic on a gun, there’s no getting past that. Of course, looks aren’t everything. It’s functionality that we’re after. Instead of the keyholes that the KeyMod utilizes, the M-LOK uses unique slots designed to attach polymer accessories without fail, namely, those made by Magpul.

In fact, many Magpul products weren’t compatible with Keymod rails which was a large driving force in the development of the M-LOK by Magpul. M-LOK uses a similar concept for locking down accessories as Keymod. The difference lies in the bi-directional swivels of the locking lugs. When tightened, the lug rotates, so you have to hold that down from the inside of the handguard while tightening screws down which greatly aids in keeping accessories held down firmly in place. 

M-LOK Cons

There aren’t many cons we have to note about the M-LOK. Though M-LOK has fantastic reliability in keeping accessories on its rail, it’s certainly not easy. The more accessories you put on your gun, the more difficult it becomes to access the locking lugs within the rail. Let’s say you want to change the placement of a rail panel, handstop, or some sort of foregrip… it’s definitely easier to mount accessories than it is to remove them.

Our Recommendation

It is our opinion, and likely the shared opinion of this industry as a whole, that Keymod is pretty dead if not on its way to being there permanently. Part of the allure of any reliable piece of hardware or firearm accessory is that it won’t fall into pieces just because you bumped it into a wall or dropped it on the ground once. However, despite Crane’s report and analysis, for 99% of shooters both rails will hold up just fine.

Ultimately, the US Special Operations Command selected the M-LOK for their reliability over the Keymod handguards and that’s reason enough for us (even though we think keymod is really just kind of ugly). SOCOM’s stress testing revealed that the M-LOK system held up better against cyclic forces, secured accessories better against high vibrational loads, accessories remained thoroughly attached when dropped, and had a better return to zero for optics. 

But another caveat is that keymod was never designed to hold precision optics as all rails will still have the 1913 picatinny rail at the 12 o’clock position. The picatinny is never going away until the AR-15/M4 gets phased out for future space guns. So regardless of keymod or m-lok being used, you’re going to be able to mount your optics, sights, and or laser on the top rail. 

We would choose an M-LOK rail for its better function and better form and there are far more M-LOK rails on the market today than there are Keymod which means more options and support. But some companies still do offer keymod like BCM’s KMR Alpha 15. If you already have a rifle with a keymod rail on it there’s no need to change that out for a new m-lok one. Just know what the rail can and can’t do in terms of its durability and reliability.