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What Is an M-Lok Rail Handguard (And Why You Need One)

L.p. Brezny | Updated November 4, 2023 | Why You Should Trust Us | How We Earn Money
Cover photo showing various extremely versatile mounting hardware options

Although buying a gun is exciting by itself, sometimes, the accessories are just as thrilling. Picatinny rails used to be the gold standard, but M-Lok is ready to dethrone the reigning champ. So, let’s take a closer look and discover why this system is becoming so popular. 

What is MLok Rail?

An M-Lok rail system is a semi-permanent attachment you can fix to virtually any gun (although often an AR-15 rifle). The rail allows you to fix any accessory to your firearm, such as an optic sight, flashlight, handguard, or bipod.

M-Lok stands for Modular Lock, and its design enables you to position your attachments as you see fit. As long as there is a negative space available, you can mount accessories to the rifle. 

Benefits of the M-Lok Rail System

The M-Lok is a relatively new rail system, so it has some advantages you can’t find with older models like the Picatinny Rail (more on that later). Here’s a rundown of the various benefits you can expect: 

  • Attach to the Handguard Directly – Sometimes, you don’t want a full-length rail system weighing your gun down. An M-Lok allows you to attach a small section to the handguard instead. 
  • Smooth Facade – Other rails like the Picatinny have a “cheese grater” feel to them, which can be uncomfortable or tricky to manage. The M-Lok has a smoother surface for better comfort and convenience. 
  • Dual-Sided System – Older rail systems are unidirectional, meaning you have to mount to either the front or the back. M-Lok systems allow you to pick a side so you can install it faster and mount accessories more easily. 

M-Lok Pros and Cons

Showing a standard m-lok standard slot system


  • Lightweight and easy to install
  • Omnidirectional spaces for better accessory mounting
  • Smooth facade feels better against the hand
  • Works with metal and non-metal M-Lok accessories
  • Built tough to withstand heavy recoil without coming loose


  • Removing accessories can be tricky at times

Top Accessories for the M-Lok Rail

Because the M-Lok system is quickly becoming a hot commodity, more and more manufacturers are building attachments for it. Here are some of the top-selling accessories to attach to M-Lok mounting systems. 

  • Vertical Grip – Front vertical grips help with shot accuracy and recoil absorption. 
  • Optical Sights – You can buy M-Lok conversion attachments to use a Picatinny Rail sight without having to install the older system. Optical sights can come with thermal vision, night vision, or variable zoom options. 
  • Flashlight Mount – Lights are often best suited for tactical shooting, but they can work for nighttime shot practice as well. 

How Does an M-Lok Handguard Work? 

Close up of the m-lok design showing off its universal compatibility

The M-Lok mounting system works as a handguard, allowing you to hold the barrel of your rifle without burning your hand. Once you install the system to your gun, M-Lok mounts accessories in any one of the slots. 

To attach an accessory, you simply use the attachment’s T-nut mounting plates to fix the piece to the inside of the M-Lok slots. Then, you use a screwdriver to turn the nut so it stays in place. You reverse the process to detach the piece as needed. 

How to Install an M-Lok: Explained

One of the main advantages of this system is that it’s a free-floating piece that slides over your rifle barrel. You may have to attach a barrel extension, but otherwise, you put the M-Lok over the barrel, tighten the screws, and secure it in place. 

Ideally, you can remove the barrel from your rifle first to facilitate an easier installation. Here’s a video showing the entire process from start to finish. 

A History of the M-Lok System

So, this rail system dates back to 2007, when Magpul adapted their MOE system to be more accommodating and easier to use. M-Lok took inspiration from the Masada Concept Rifle, but it would take another seven years before the M-Lok rail we know today existed. 


This is the technical term for the Picatinny Rail, which was developed in 1995. This rail became the standard mounting option for military and police weapons, and it also was available for consumer firearms.

As we’ll discuss, the original Picatinny Rail worked well as a modular system, but it was inherently heavy and uncomfortable. So, something like M-Lok was a welcome change to the traditional method. 

M-Lok Specifications

Here’s a quick overview of the different specifications you can find on an M-Lok accessory rail: 

  • Slot Length – 1.26 in
  • Slot Width – 7mm (0.276 in)
  • Space Between Slits – 8mm (0.315 in)

M-Lok vs. Picatinny Rail System

Since M-Lok looks to be replacing the old Picatinny Rail system, let’s look at a few of the ways these two models differ: 

  • Weight – M-Lok is much lighter and more agile than Picatinny, all without losing durability or resilience. 
  • Comfort – A Picatinny Rail comes with sharp edges, and new rails can sometimes cut the shooter. That doesn’t happen with an M-Lok. 
  • Durability – Both systems are strong and dependable, but the Picatinny is a bit more rugged than the M-Lok. However, it’s designed for heavy-duty rifles and applications (i.e., warzones), so it has to be reliable. 

KeyMod vs. M-Lok

Image comparing the key mod system vs m-lok products accessory attachment capabilities

Another more recent player in the accessory rail system industry is KeyMod. This rail is similar to M-Lok, but it’s a bit lighter and more nimble. 

Overall, KeyMod is meant for fast action and quick engagements. It’s light and allows for seamless attachment, making it perfect for competitions and personal use. 

That said, for military applications or resilience tests, KeyMod is too light to be super effective. Plus, in drop tests, many attachments can separate from the rail, which is a huge problem in the field. (1)

Mlok Rail vs Keymod

If you’re interested in hearing more on the mlok rail vs keymod systems, our article on the topic will make things much more clear.

Best AR15 Hanguard

Now that you know about M-Loks, the next step is to check out our articles on the best AR15 hanguard options on the market.


What mm is a 15” M-Lok rail?

A 15-inch M-Lok rail will have a 33 mm diameter, meaning it will fit over any AR-15 or similar rifle. Even with a relatively long shaft, this size rail only weighs 8.6 ounces. 

What is the 12” Free Float Super Slim M-Lok rail system?

The 12” Free Float Super Slim M-Lok Rail is a 12-inch rail that installs around the barrel of an AR-15 rifle. This particular rail is super lightweight and easy to use. 

What is an M-Lok Split rail?

An M-Lok split rail has two sections with fixed Picatinny-style ridges instead of ridges all the way along the top of the system. In the center are more negative spaces for fixing attachments. 

Is M-Lok the same as a Picatinny? 

No, M-Lok and Picatinny rails are two separate systems that allow users to attach add-ons to their rifles. 

What is the purpose of an M-Lok system?

The purpose of an M-Lok system is to allow you to attach accessories to your rifle, such as scopes, flashlights, handles, and more. 

Are M-Lok rails better? 

M-Lok rails are better than KeyMod and Picatinny for different reasons. However, if you’re talking about heavy-duty performance, a Picatinny Rail is better. 

What does M-Lok mean on a rifle?

M-Lok means Modular Lock, indicating the modular sections you can use to attach accessories like optics, flashlights, handles, and more. 


  1. Firearm Blog, Crane-M-LOK-vs-KeyMod, retrieved from https://www.thefirearmblog.com/blog/wp-content/uploads/2017/05/Crane-M-LOK-vs-KeyMod.pdf

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