RailScales® est. 2014

The Rail in RailScales

The Rail in RailScales

December 22, 2016

Let’s talk rails. They are, as our company’s name implies, a pretty important AR 15 component to us here at RailScales. Without a rail system, our namesake scales and handstops would be pretty ineffective, as we’d have nowhere on the AR 15 to attach our awesome accessories. With that in mind, the various rail systems available for AR 15s are an important foundational piece to both your firearm and our business.

What It Is

The rail system - the technical term for it is Rail Interface System (RIS), or sometimes the Rail Accessory System (RAS) - is that handy system that allows you to add attachments such as handstops, bipods, or sights to the upper of your AR 15. A rail system is two or four rows of ridges and valleys (which look like railroad ties, thus the name) or evenly spaced holes to which you can attach any number of accessories.

The idea is that, by creating an AR 15 modifier with regularly sized and spaced holes, it should be easier for any owner to add other AR 15 rail accessories to modify your firearm just the way you want it, without costly installation assistance or permanent modification. And that, in essence, is the beauty of the AR 15; it’s one of the most customizable firearms available.

What It Does

A rail system is often used in place of a basic handguard. Rails do not necessarily provide any additional heat protection the way a handguard does, though many can. However, a rail system offers a great deal more customizability in terms of custom AR parts and other AR 15 rail accessories that you can attach to the rail. This means that you can not only add a head protection, such as our patented RailScales, you can add other accessories to your AR 15 as well.  

Rail systems come in either “drop-in” or free-floating varieties, both of which come with quad-rail, double-rail, or single rail options. Depending on the make and material, free-floating rails can be a bit heavier and more expensive, but they generally allow more customizability and more stability, particularly for optics.

A Quick History

The most prevalent rail systems available for AR 15s currently are the Picatinny (MIL-STD 1913), KeyMod, and M-LOK. Both the KeyMod and the M-LOK systems seek to improve upon the Picatinny system’s bulk and heaviness. Both KeyMod and M-LOK have their own advantages:


This rail system is pretty easily recognizable on sight; this is the modular rail system with a series of holes shaped like stylized old keyholes. It was originally designed by VLTOR Weapons Systems and is a series of holes across the top, sides, and bottom which allow for direct attachment of KeyMod handstops, rail scales, and other AR 15 rail accessories. The KeyMod system even offers varieties with 45-degree slots for mounting options in any direction. If you have accessories that are designed to fit the older Picatinny rails, you can get KeyMod compatible Picatinny-style rails that easily attach so you don’t lose any functionality. The perks of the KeyMod rail system are:

  • They are easily compatible with most accessories with less bulk than Picatinny rails
  • They offer stability with less weight than the Picatinny system
  • The design is open-source so many AR 15 accessory manufacturers make KeyMod compatible accessories less expensively

With the KeyMod system, you can easily attach KeyMod hand stops, rail scales, or other accessories. Simply insert the nuts into the wide end of the holes, slide into the narrower end, and tighten to secure. If you have Picatinny-compatible accessories, there are attachments as small as three rails up to the full length of the rail system, so you can add as little extra weight and bulk as possible.


M-LOK, designed by Magpul Industries, is an AR 15 accessory mounting system, that mounts in negative space in a similar manner to the KeyMod system. Both stand in direct opposition to the Picatinny system, which mount on rails that extend out. Again, like the KeyMod system, the M-LOK rail system seeks to cut down on the weight and dimension necessary with the Picatinny rail system. However, unlike the KeyMod system, the M-LOK system uses a series of narrow slots and bi-directional T-slot nuts rather than key-shaped holes. The idea behind it is that the T-slot nuts allow for easy installation of accessories and, thanks to the t-shaped nuts, means the accessories can be installed at the front or back of the slots.

The M-LOK system offers:

  • Easy installation of AR 15 rail accessories
  • Is sleeker and less heavy than the Picatinny system
  • The design isn’t open source, but it is free-license, so accessory makers can get ahold of the license pretty easily and don’t have to pay for it
Because we know you’re looking to cut down on weight and bulk, RailScales makes AR 15 rail grips and hand stops that are easily compatible with both KeyMod and M-LOK. Simply select your preference in the checkout process and you can have KeyMod handstops and rail scales or M-LOK compatible options. Our rail scales and handstops are lightweight, thin to keep that low profile, and heat resistant to protect your hands without adding weight. Shop RailScales for KeyMod and M-LOK rail scales and handstops today!