Picatinny! Free-float. M-LOK! What does it all mean?
This guide compares KeyMod vs. M-LOK vs. Picatinny handguards. We’ll explain the differences between a free-float and drop-in handguard, and we’ll break down the differences between all three types of AR-15 handguards (military test results included!) so you know which one to pick for your rifle or pistol.
Let’s take a look at each type of system:
What is M-LOK?
M-LOK (which stands for Modular Lock) is a modular, universal rail system created by Magpul Industries and brought to market in 2014. M-LOK works by using the voids between the handguard and the barrel as the space for attaching for your accessories and optics. The M-LOK attachment points use rounded rectangular holes. M-LOK says this design is superior to KeyMod handguards.
Magpul say the major benefit to their rail design is the ability to reliably attach polymer and plastic accessories. They say the KeyMod’s conical attachment nuts don’t do a good job of securing polymer accessories. Speaking of attaching things, let’s see exactly how M-LOK works with most accessories:
How M-LOK Works
M-LOK uses a system of rotating, locking T-nuts and simple torque specs to secure accessories to the rail. Pictured below is an example of an M-LOK accessory attachment system. Note the two T-nuts threaded onto either end of the small accessory (in this case, a sling adapter).
How to install an M-LOK accessory
- Orient the T-nuts so they’re parallel with the M-LOK attachment hole (pictured).
- Place the accessory atop the attachment hole location you want to secure it to.
- Use a hex wrench / Allen key to rotate the T-nut 90 degrees, so it’s perpendicular to the opening.
- Tighten the T-nut to the appropriate torque settings:
- Metal accessory to metal handguard: 35 in/lbs (3 ft/lbs).
- Polymer or metal accessory to polymer handguard: 15 in/lbs (1.25 ft/lbs).
- Polymer accessory to metal handguard: 15 in/lbs (1.25 ft/lbs)
What is KeyMod?
KeyMod is a universal rail system developed by VLTOR, a high-end weapon systems company, and introduced by Noveske Rifleworks. Their design was intended to supersede the Picatinny/M1913 rail system. As such, the KeyMod rail system is open-source: It’s freely available to any manufacturer in the public domain, so anyone can develop accessories, rails, and attachment systems that work with KeyMod, at no extra cost.
KeyMod aptly gets its name from its own design: The system is modular, allowing different lengths of accessories to be installed on a single rail, and it uses a key-hole method of tightening and attaching things.
How KeyMod Works
KeyMod works in similar fashion to M-LOK, using clamping pressure and torque specs to keep things in place. Importantly, KeyMod is different from M-LOK in one way: It doesn’t use flat-faced attachment points. Unlike the T-nuts on the M-LOK system, the nuts used to secure KeyMod accessories feature an angled protrusion (pictured on the rail accessory below). On the underside of the KeyMod handguard, the slot is chamfered, or angle-cut. This angle-cut is meant to match the angled protrusion on the KeyMod nuts, locking the accessory into place (like a key).
Once tightened, this creates a very strong attachment point that resists high amounts of recoil and slippage. KeyMod also claims this method boasts high “repeatability”. This means that once an accessory is removed and reinstalled later, it’ll reliably re-secure in that same, exact position without any fine-tuning or adjustment. This is important for zeroed optics and iron sights.
M-LOK Vs. KeyMod: Which is Better?
This is the question everyone’s been asking. It’s difficult to answer because both systems are lightweight, universally compatible, and easy to use.
We like M-LOK more than KeyMod for two reasons.
First, M-LOK is supported by Magpul, one of the biggest names in the industry. Magpul supplies to the U.S. Military and law enforcement, and they take a huge share of the tactical rifle and accessories market. The M-LOK system is going to be more compatible with all the stuff you might buy for your AR-15.
Second, The U.S. Military conducted failure tests with M-LOK and KeyMod before choosing one system for their own rifles. The stress testing showed that M-LOK rifles could be dropped on the ground and the accessories on the rail would stay in place, tightened, 100% of the time. KeyMod accessories only stayed in place 33% of the time.
You can download the full handguard test and results from the U.S. Military, here.
What is Picatinny?
Ah, the classic hand guard and rail system. The Picatinny rail has been around for decades. Officially called the MIL-STD-1913 rail, the Picatinny rail continues to be one of the most common attachment systems on tactical rifles and pistols, and not just on the AR-15. The name comes from Picatinny Arsenal in New Jersey, the company tasked in 1992 with developing this standardized rail system for the U.S. Army.
How M1913 Rails Work
Unlike M-LOK and KeyMod handguards, which use the negative space/void between the handguard and barrel to attach accessories, the Picatinny system uses raised rails that sit on all four sides of the handguard. These rails contain a series of raised bars with angled sides. They act the mounting point for each accessory. The accessory being attached to the Picatinny system uses a clamping system that “bites down” on either side of the Picatinny rail. A set screw is then tightened, securing the accessory to the rail, pictured below.
This attachment system requires much more steel and/or aluminum to be used in the construction of the rail and accessory in question. But what the Picatinny system loses in weight, it makes up for with the most secure attachment method of the three, by far. Once you lock down an accessory to a Picatinny rail, you’re more likely to break the handguard or accessory itself, before breaking the connection between the accessory and the rail.
Which Handguard is Best for Me?
None of these three rails is better than the other two by all measures. Each has its own pros and cons:
Most Universal: M-LOK
The M-LOK system wins in the compatibility department. It’s supported by Magpul, so it enjoys a huge market share. Most accessories will be compatible with M-LOK over KeyMod.
Most Affordable: KeyMod
Because KeyMod is less popular than M-LOK, it tends to be more affordable. If you’re trying to save cash or simply don’t want to spend as much money as possible on your AR-15, it may be worth considering a KeyMod rail over an M-LOK unit.
Toughest, Mil-Spec: Picatinny/M1913
For the shooters who want an indestructible rail setup, Picatinny is the way to go. There are free-float Picatinny systems out there, so you won’t lose accuracy compared to a KeyMod or M-LOK rail. The Picatinny rail system is simply heavier than the other two.
- KeyMod and M-LOK handguards are universally compatible, lightweight options.
- M-LOK beats out KeyMod for overall compatibility and performance from drops and mishaps.
- Picatinny is the good ole’ rail system that’s bomb-proof and tougher than the other two.