Rail Roundup: About the Main Types of Firearm Rail Systems

The majority of modern firearms, especially those destined for tactical roles supporting law enforcement and military personnel, are equipped with multiple mounting points or rail systems.

As is commonly the case with infantry rifles, the handguard of the rifle is merged with the rail system, resulting in a component that performs both offices - it shrouds the barrel and it also serves as a mounting point for shooting accessories like optics, lights, and more.

While not all rifles are equipped with handguards that have integral rail systems, most do, and most of those sport one of the following three types of rail systems, which will be detailed here.

Developed at New Jersey’s Picatinny Arsenal in the 1990s and standardized as MIL-STD 1913 in 1995, the Picatinny rail system is one of the most ubiquitous in the market, despite its age.

The Picatinny rail, also known as a “Pic” rail, consists of a series of deep slots and grooves that can accept a wide range of attachments. Typically, they are made of aluminum or some heavy polymer.

To mount an accessory on a Pic rail, the operator must slide the claw or mount over the rail, position forward or backward, and tighten the bolts that secure it over the rail’s ridges and grooves.

In this manner, Picatinny rail systems are highly modular and versatile. Since they have been around for 30 years now, there is also a very wide range of accessories that are compatible with them.

The vast majority of optics are compatible with Picatinny rail systems, and many weapon lights, vert grips, mounts and adapters are as well. All in all, it is likely that more accessories are compatible with Pic rails than with any other configuration.

Because of its heavier construction, Picatinny rails are generally considered the strongest of the rail systems mentioned here, and as a general rule they afford the best interface for mounting optics over the receiver. This is why, even up to the present day, many tactical platforms have a section of Pic rail mounted over the receiver.

That weight, however, can also be considered a detractor, as a rifle with a Pic rail handguard could weigh significantly more than one with an M-LOK or KeyMod system. Moreover, deeper slots and grooves of a Pic rail are more likely to get snagged on gear, and some operators consider them less comfortable to use without gloves. For that malady, there are two options; one is a shorter handguard, and the other is a set of Picatinny rail covers. The problem with the latter, though, is that they add even more weight to the rifle.

So, that being the case, what are the relative strengths of the other two common rail systems?

M-LOK rail systems, also typically made from aluminum, consist of a lower profile structure into which are integrated a series of lozenge-shaped slots. To mount an accessory on an M-LOK rail system, you insert the attachment’s T-shaped lug, slide it where you want it to go, and tighten it.

Overall, the best selling point of the M-LOK rail system is that it is much, much lighter than a traditional Picatinny rail. In addition to the weight savings, most users also appreciate the ergonomics; instead of the rough, sharp edges of the Pic rail’s ridges, the M-LOK rail’s slots are smooth, with chamfered edges. They are much more comfortable to hold, even without gloves.

M-LOK rails are less expensive to produce than Pic rails, but there’s a catch. Since they are newer and the product is not open-source, manufacturers need to pay more to develop accessories. As a result there are fewer accessories for M-LOK mount, but more are being added to the market every year, so in time, that should even out.

Lastly, we’ll cover KeyMod rail systems, which were developed in 2012 by VLTOR Weapon Systems and Noveske Rifleworks, and which are an open-source project, which means basically any manufacturer can produce attachments that are compatible with KeyMod systems, fairly cost-effectively.

Like M-LOK rail systems, KeyMod rails are usually made with aluminum, are typically very lightweight, and have a series of slots. However, in the KeyMod rail system, the slots are pear-shaped and wider at one end, unlike the symmetrical, lozenge-shaped slots of the M-LOK.

This means KeyMod accessories can only be inserted and therefore installed one way. It’s still easy, though; you line up the lugs, insert, and tighten the screws or bolts to secure it in place.

Like the M-LOK, there aren’t as many accessories for KeyMod rails, but that is changing with each passing year as more and more manufacturers make KeyMod compatible attachments.

It’s also worth noting that both M-LOK and KeyMod rail covers are less snag-prone than Picatinny systems.

At Kiesler Police Supply, we carry a wide range of shooting attachments and accessories for M-LOK and Picatinny rail systems. For more information on our catalog or available shooting attachments, visit the previous link or get in touch directly with one of our representatives.