In this informational guide, let's discuss KeyMod VS M LOK design, pros and cons , and at the end you can decide which system is better.
Additionally, we are going to attach the study & research done by NSWC Crane from 2017 that went in depth on the longevity and reliability of each mounting system using various mounts available on the market.
Let's get started.
Difference Between KeyMod and M LOK
The two mounting systems both work great for most people and it will not affect the way you shoot whatsoever.
When the military spends millions of dollars to develop the next level ultra durable system doesn't mean the end users need to upgrade to stay up to date.
KeyMod works like a Gorilla rack, the big part slides plugs into the "Key hole" first, then the shoe shaped chamfered nut cams and clicks in place. Finally tighten the two screws for a secured mount.
The raised recoil lug protrudes into the slot. AS the bolt is tightened the nut wedges the recoil back against the opposite end of the slot to create a compression forward & rearward solid mounting solution.
The KeyMod system is designed by Eric Kincel (VLTOR Weapon System) to supersede the M1913 rail system for a more modular attachment interface. The suffix "Mod" comes from the name trend of VLTOR accessories, and "Key" reference to the key hole profile of the mounting slots.
- 1st NEW innovative way to mount accessories since M1913 rail
- Plenty of KeyMod accessories available
- Locks On Tight
- Very modular
- Reduced handguard weight, manufacturing cost & time
- KeyMod mounting accessories without recoil lug will not withstand recoil & vibration for long
- Non chamfered nut can create pressure point and damage the handguard rail
- Poor repeatability for mounting precision laser devices
- Some mount accessories have unflexible mounting positions compared to M1913 (Unless using a sectional KeyMod based M1913 rail piece)
- Required tools (No Quick Detach)
The M LOK works similar to the KeyMod, and the two squared T nuts work like strut nuts by tightening them through the rounded rectangle mount slot and it holds it in place via two locking lugs.
The M LOK system stands for Modular Lock developed by Magpul Industries that allows for direct accessory attachment onto the "negative space" hollow slot mounting points
- Flexible orientation on free float handguards
- Plenty of M LOK accessories available
- Improved repeatability for mounting precision laser devices
- Reduced handguard weight, manufacturing cost
- Reduced machining complexity compared to KeyMod
- Very modular
- Installation can be frustrating if the cam locking nut is free spinning without making contact with the mount slot
- Doesn't work with Magpul MOE system
- Some mount accessories have unflexible mounting positions compared to M1913 (Unless using a sectional M LOK based M1913 rail piece)
- Required tools (No durable Quick Detach option available)
Recommended Torque Specs For KeyMod & M LOK
M LOK Screw Torque Spec
For secured mounting please following this spec (Gathered from various sources and pros recommendation in the firearm communities):
- For metal accessories to metal handguard - 30 - 35 in/lbs
- For Polymer to metal or polymer to polymer - 15 in/lbs (actually 8 in/lbs is enough based on experience)
KeyMod Screw Torque Spec
Features Fix It Sticks
- For metal accessories to metal handguard - 18- 20 in/lbs (Over tightening can damage the noteched cross bolt)
- For Polymer to metal accessories or polymer handguard - 15 in/lbs (8 in/lbs is actually enough to prevent crushing the polymer)
Get this AVID Smart Torque wrench so you know exactly how much in-lb is applied to the screw
Both mounting systems provide the user the ultimate weapon modularity, and it keeps the handguard smooth, lightweight and clean.
The user can go from:
- KeyMod to Picatinny
- MLOK to Picatinny
- KeyMod OR MLOK ONLY
Whatever accessories you want to add, you just add, and whatever you don't want, you just take it off. They are a major leap forward in weapon design than the traditional M1913 full length rail handguard.
As far as installing and removing accessories go.
However, as we mentioned above that currently both systems require tools for installation and removal, and not many Quick Detach ones are available on the market.
Check out best AR15 handguards here.
Both mounting systems are either made with aluminum or polymer, and they are all durable without any issue.
Based on NSWC Crane's testing for the USSOCOM, the M-LOK is comparable in endurance and rough handling testing, but it greatly outperformed KeyMod in repeatability, drop testing and failure load testing.
If you want to read the full test from start to finish, please check out the NavSea Warfare Centers Crane test results here.
6 drops per handguard of 6 specific orientations from 5 ft with weapon light installed at 9 o'clock on the handguard in forward most position
- 100% MLOK accessories remained attached
- 33% KeyMod accessories remained attached
- MLOK system achieved a 73% improvement in average POA shift over KeyMod
- The average MLOK test failure load over 3X the average KeyMod
- All KeyMod failure occurred at the interface between the handguard and accessory rail
- All MLOK tests failed at weapon light mount or mount to accessory rail interface
Both KeyMod & MLOK exceeds the cyclic load test where the material is induced to strain, shear, stress and deformation.
Precision machined aluminum ones are definitely stronger and harder to handle normal rough handling, and it's recommended for mounting precision laser devices for repeatable zero.
When mounting a laser device to the M LOK based M1913 rail section, please make sure the mount has applied pressure down and towards the front of the gun as you're tightening the screws, just like how we mount an optic on the top rail.
Available Accessories & Quick Tips
There are many different types of weapon configurations and specs, and you may encounter some problems with the M LOK system, where the bolt is too long that interferes with the rifle gas block or the barrel if its sitting too close.
The best way to fix these types of problems is to try different mounts or swap out screws for the best possible result.
KeyMod & M LOK accessories are very popular for:
- Sling attachment point
- Bipod mount
- Offset optic mount
- Light mount
- Pressure switches
- Rail cover
- M1913 rail section
Some of these accessories are covered in our popular AR15 accessories guide, which you can check out here.
The modular attachment design has made many rifle configurations lighter, more slick and higher speed. Once you have decided on one system, it's much economical to stick with that system for all of your other guns so all accessories can be cross shared from one platform to another.
There is no need to upgrade from KeyMod to M Lok or vice versa by keeping up to date with what the military has. At the end of the day, both systems work very well and they will not affect how you shoot the rifle at all.
As far as durability goes, they're equally good for providing solid modular mounting solutions, but when it comes to improved zero repeatability for laser devices and surviving drops, the M LOK is a better choice overall.
Check out more AR15 complete upper receivers with rock solid handguards
As the content creator of badassoptic.com, My background in the firearms industry and shooting sports gives me the experience to recommend tried and true products and keep away subpar ones.