Accessory mounting interfaces: evolution from Weaver to M-LOK

Modern Firearms and Mounting Interfaces: From Weaver to M-LOK

Modern firearms must meet the demands of specific tasks, and since there’s no one-size-fits-all setup, the ability to reconfigure a weapon is what truly sets modern firearms apart from traditional ones. Numerous auxiliary accessories can be useful to both competitive shooters and military personnel alike, which raises an important question: how do you attach them to the weapon? Put away your duct tape and zip ties, because today we’ll take a close look at the mounting solutions used by KPYK.

A Brief History of Mounting Interfaces

The history of mounting accessories to firearms can be traced as far back as one wishes, but we’ll start our timeline with something more relevant—the Weaver rail.

Weaver Optics has been producing rifle scopes for decades. Its founder, William Ralph Weaver, also created the Weaver rail—a mounting system designed for his scopes. The interface was intended for mounting optics on hunting rifles, eliminating the need for custom-fitting and drilling. This made it the first widely adopted standard in the industry. While many manufacturers had their own incompatible mounting solutions, Weaver emerged as a de facto "gold standard" for a time, especially for optics. It’s worth noting that the Weaver rail has some dimensional specifics, which must be considered when choosing attachments.

The Picatinny rail resembles the Weaver in design, but they are not fully interchangeable. Weaver slots are 0.180 inches (4.37 mm) wide and are spaced inconsistently, while Picatinny slots are 0.206 inches (5.23 mm) wide with a standardized center-to-center spacing of 0.394 inches (10.01 mm).

In Ukraine today, Weaver rails are most often found on older hunting shotguns or on more budget-friendly firearms.

The U.S. military officially adopted the Picatinny rail in early 1995. Known under the MIL-STD-1913 standard, it provided strict specifications that significantly improved cross-compatibility (assuming manufacturers adhered to the standard).

The interface was also adopted as a NATO standard and has proven itself over the years of use. While it adds some weight to the firearm, its reliability and compatibility far outweigh this drawback.

At KPYK, we strictly follow the Picatinny standard when producing rails in various lengths—from 3 to 19 slots—and apply a Cerakote finish to ensure your accessories not only mount securely but also look great.

Example of the efficient combination of interfaces - both 1913 rails and M-LOK work together to provide a boost to capabilities

M-LOK Mounting: History and Application

The M-LOK interface began in 2009 when Magpul introduced their MOE (Magpul Original Equipment) handguard system, designed to eliminate the need for external Weaver or Picatinny rails. A similar concept was later introduced by VLTOR Weapon Systems in 2012 under the name KeyMod.

After evaluating competing designs, Magpul released the improved M-LOK system in 2014. This modern interface allows direct attachment of accessories to the handguard, saving weight by eliminating the need for an additional rail.

At KPYK, we manufacture handguards for AK and AR-platform carbines that use the M-LOK system, enabling users to mount compatible accessories directly and efficiently.

Pros and Cons: Weaver-Picatinny vs. M-LOK

Now that we’ve discussed the advantages, it’s time to consider the drawbacks of these mounting systems.

Starting with the Weaver rail, its inconsistent manufacturing standards led to compatibility issues. One accessory might mount securely to one manufacturer’s rail but not fit another’s.

As for the Picatinny interface, its main disadvantages are bulk and weight. These become critical issues if you need a full-length rail on your handguard. Also, the grooves can be uncomfortable to hold for extended periods, prompting the creation of now-iconic quad rail covers that protect users’ hands and gloves from sharp edges.

While M-LOK was designed to simplify accessory mounting and reduce weight, it’s not without its own quirks. For example, Picatinny-compatible devices often feature large thumb screws that can be tightened or removed by hand. In contrast, M-LOK uses smaller screws and T-nuts that typically require a tool. Compatibility with older accessories is also limited, although in practice, this is rarely a major issue.

Final Thoughts

When choosing a mounting standard, it’s important to understand which accessories you plan to use and for what purpose. The best option is to try all the available systems firsthand and choose the one that works best for you.