For a number of years following the end of the Assault Weapons Ban in the United States, the Picatinny rail system was the only viable option for the AR-15 weapon platform. While the Picatinny system allowed for the attachment of various accessories, the rail system was overly bulky and added considerable weight, which created concern for rifle owners increasingly on the go. This left the door open for innovation, and over roughly the last decade, the bulk of the AR-15 rail systems have shifted to the more modern Keymod or MLOK rail attachment style. While both of these options allow for accessory attachment directly to the rail, as well as making the overall weight of the weapon considerably lighter and less bulky, they have some important differences that a discerning gun owner should consider before committing to a new AR-15.

Keymod vs MLOK System - Differentiating Factors

Surprisingly, there is very little difference between MLOK and the KeyMod rails on the surface. The MLOK, or modular lock, was developed by Magpul in 2014. It uses T-nuts and rectangular slots that make the attachment to the rail quick and secure. These T-shaped nuts are placed into the slot, turned, and then lay across the slot, locking them in place. MLOK more closely resembles the Picatinny system because this rail system uses compression force to hold items in place. The MLOK system also offers a dual-point attachment platform that allows for accessories such as lights and foregrips to be mounted with a lot of flexibility for personal preference and comfort. MLOK systems are designed to get the most output from the least amount of material. This helps with weight, but it also helps to reduce the cost, making it a popular choice for budget-conscious shooters. The final benefit to make note of, Magpul’s choice to make the designs open-source, allowing designers, engineers, and arsenals everywhere to produce parts and accessories for it without the need for an adaptor.

Alternatively, KeyMod is named after the shape of its slots, which look like a keyhole. These rail systems work by using conical lugs and key-shaped holes, and they secure a rail system in addition to a multitude of accessories directly to the handguard itself. Simply put the accessory's lug in the opening and slide forward, using a wrench to tighten it up. The slots and lugs face the muzzle, which helps to ensure they don't fly off from the recoil of the firearm. The KeyMod system is a lightweight, modular attachment that only requires you to deploy a rail section large enough to mount the hardware you need. Additionally, all of its angles and cuts are in the interior of the handguard, allowing for more comfort without needing to have rail covers mounted.

MLOK Rail Accessories Overtaking Market Share

During testing for the Advanced Sniper Rifle Programs, MLOK accessories performed at a higher level than Keymod on a regular basis. Due to its reliability and ease of use, it was selected for use on the Suppressed Upper Receiver Groups for military use and soon became a more popular option in the civilian market as well. While there are still many Keymod systems in use today, the availability of accessories has started to dwindle over the last few years as the bulk of new AR-15s produced has now opted to go with the MLOK system. 

Rail Accessories For All Types

RailScales offers rail covers, as well as many other AR-15 accessories for both the MLOK and the KeyMod systems, so no matter customer preference, RailScales has an option to enhance the function and aesthetic. Where many companies have opted to discontinue their Keymod accessory options, RailScales continues to make products available for multiple attachment platforms, and even uses their COG multi-mount system to make moving certain accessories from Keymod to MLOK seamless.