A few carefully selected accessories can transform an AR-15 rifle into a tool perfectly suited to your needs. A variety of accessories can be attached to the rifle — from bipods to lights and optics — but first of all you need to decide how to mount them.

There are three main mounting systems for AR-15s today: the Picatinny rail, KeyMods mounts, and M-Lok mounts.

A veteran in this field is the Picatinny platform, which has been widely used since its invention in the early 1990s. The MIL-STD-1913 rail, as it is commonly known, was designed by Picatinny Arsenal in New Jersey at the request of the US Army. The company, which is owned by the federal government and managed by the US Department of Defense, was looking for a reliable mounting system for mounting sights on large-caliber rifles. Currently, the Picatinny platform can be used to mount a wide variety of weapons and accessories, including bipods, lights, sights, etc.

Despite the significant advantages, the Picatinny platform has a number of disadvantages. The most significant of which is the extra weight in the front of the rifle.

The possibility of eliminating this drawback is offered by two new mounting systems that offer similar mounting options, but with smaller profiles and weight. These are the KeyMod and M-Lok systems.

Let's take a look at the difference between the KeyMod and M-Lok mounting systems so you can make an informed choice between them.

picatinny rail

Handguard with Picatinny mounting system

 

KeyMod

The KeyMod mounting system got its name from the mounting slots that resemble the shape of a keyhole and modular construction.

The first KeyMod platform was released in 2012 by VLTOR Weapon Systems and Noveske Rifleworks with the goal of "standardizing mounting systems in the firearms accessory market."

KeyMod is an open source system that allows any manufacturer to produce accessories using this system without obtaining permission from the inventors and without paying them royalties.

 

Choose a forend or other accessories compatible with the KeyMod system in our online store:
- KeyMod forearms from Big Dragon, Specna Arms, Ares or LayLax;
- Big Dragon, Ares or FMA grips;
- Big Dragon swivels.

 

Advantages of the KeyMod system

  • light weight;

  • support for all types of fasteners;

  • easy to install accessories — you just need to insert the tips of a compatible accessory into the wide end of the keyhole, slide them to the narrow end and tighten with a screw.

 

Disadvantages of the KeyMod design

The main disadvantage of this system is that it does not have the same level of support from the firearms industry as other platforms such as M-Lok. The KeyMod system supports all types of mounts, but it is not supported by as many directly compatible products as other platforms.

In theory, a Picatinny rail can be attached to the KeyMod system and almost any accessory can be used, but again, this will increase the weight of the rifle.

keymod handguard

Handguard with KeyMod attachment system and Picatinny top bar

 

Next, let's move on to its biggest competitor — the M-Lok fastening system.

 

M-Lok

The M-Lok mounting system was released in 2014 by Magpul, a company known for its polymer magazines for AR-15s and other gun accessories. The M-Lok system is a further development of their MOE mounting system.

The system works in much the same way as KeyMod, but with a few important differences. Namely: in the M-Lok, the KeyMod keyholes are replaced with elongated grooves, and the round KeyMod tips are replaced with T-shaped lugs.

 

Choose a stock or other accessories compatible with the M-Lok system in the Punisher online store:
- forearms from Big Dragon, ACM, Kruk or Odin Works;
- Magpul bipods;
- FMA handles;
- mounts for swivels from Magpul, Viking Tactics, BMC or Kruk.

 

Advantages of the M-Lok system

M-Lok's differences seem minor, but they give the system two significant advantages over the competition.

  1. Because the M-Lok slots have the same shape (length and width) over the entire area, you can install the necessary accessories anywhere in the slot. In this case, KeyMod will allow you to install the necessary accessory only at the narrow end of the keyhole. The flexibility provided by the M-Lok design can be really useful if you choose the right devices and accessories.

  2. According to a 2017 study by the US Special Operations Command (USSOCOM), the M-Lok system performs better. The tests compared M-Lok and KeyMod mounts made by the same manufacturer on five parameters: repeatability, endurance, rough handling, drop testing and failure load. The study found that the M-Lok outperformed the KeyMod in three out of five measures, while two showed no significant difference between the two (see table).

 

Table — Comparison of performance indicators of M-Lok and KeyMod systems

Indicator

Result

Repeatability

M-Lok achieved a 73% improvement in average POA shift over KeyMod

Endurance

KeyMod and M-Lok system performance exceeded cyclic load test conditions

Rough handling

KeyMod and M-Lok system performance exceeded cyclic load test conditions

Drop testing

  1. 100% of M-Lok accessories remained attached:

  • 1/3 M-Lok accessories remained in-place;

  • 2/3 M-Lok accessories slid rearwards but remained secure.

  1. 33% of KeyMod accessories remained attached:

  • 1/3 KeyMod accessories remained attached, but severely damaged handguard;

  • 2/3 KeyMod accessories completely detached.

Failure load

  1. Average M-Lok test failure load over 3 times greater than average KeyMod system:

  • all KeyMod failures occurred at the interface between the handguard and accessory rail;

  • all M-Lok system tests failed at weapon light mount or mount to accessory rail interface.

 

As such, the M-Lok mount has proven to be superior in "preserving accessory placement during initial and remounting", better retaining attached accessories in the event the rifle is dropped, and making mounted devices more difficult to disengage.

magpul m lok

M-Lok buttstock with Picatinny top rail

 

M-Lok vs KeyMod: Who Won?

Based on the results of the study, is it safe to say that the KeyMod system should not be used to attach accessories to a rifle? Do not rush to conclusions — first consider the following caveats.

  1. This was just one study. His results for SOCOM were convincing to favor the M-Lok system, but further testing is needed to confirm its findings.

  2. The M-Lok's superior performance in the SOCOM study depended on proper attachment installation, which, as many gun owners will attest, is noticeably more difficult to accomplish when mounting an M-Lok than when using the KeyMod system.

  3. Even if the KeyMod mounts are inferior in some respects to the M-Lok system, they will most likely be satisfactory for the average user of the AR-15 platform. The vast majority of shooters do not operate their rifles in conditions similar to real combat, and they usually do not perform regular mounting and dismounting of installed devices. It's unlikely that you're going to lunge with your rifle. But even if this happens, in most cases it is possible to reattach the hinged devices without any consequences.

 

The thing is, there are some great KeyMod mods out there, and if one of them strikes your fancy, despite the design flaws, there's nothing stopping you from giving it a try.

If you want to own the best, choose M-Lok. This is probably the most popular mounting system available on the market today. Even the military has recognized it as the best, so you'll be in great company.

 

Source: https://gunpros.com/mlok-vs-keymod/

Editing: Punisher