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Mod Squad: Is KeyMod the New Industry Forend Standard?

Mod Squad: Is KeyMod the New Industry Forend Standard?

What will replace the 1913 quad rail? A few possibilities include (from left to right): Tech Ops/Rebel Arms's T-bolt; SLR Rifleworks's rail with 1913 rails and QMod; SLR with just QMod; Geissele with 1913 rails and KeyMod; and Bravo Company rail with KeyMod.

In the not so distant past, mounting a light onto a rifle required a bit of fabrication and, quite often, hose clamps. The MIL-STD 1913 "Picatinny" rail changed all that. Developed by Richard Swan of A.R.M.S. Inc. in the 1980s, it was a refinement of William Weaver's famous Weaver mount.

Swan took the Weaver rail to the next level by tightening its tolerances and slightly changing some specifications. Swan's design was tested and evaluated by Picatinny Arsenal and standardized as the MIL-STD 1913 in February 1995. His design features a series of ridges with a T-shaped cross-section interspersed with flat spacing slots that are 0.206 inch wide. Swan's evolution of Weaver's rail proved to be ideal for mounting optics securely onto a rifle.

It didn't take long for the U.S. military to realize this system could be used for more than just mounting optics onto a rifle. Other mission-essential items such as white lights, IR laser/illuminators, bipods, vertical grips and sling attachments could also be attached. This was made possible by the introduction of the now-famous quad rail fore-end, which featured MIL-STD 1913 rails at 12, three, six and nine o'clock.

While they are largely taken for granted by younger shooters today, the importance of the development of the Picatinny itself and then the quad rail fore-end cannot be overstated. By becoming an accepted industry standard, this design — and, more importantly, accessories for it — flourished. Instead of every company building accessories to fit a proprietary system, they simply built them to fit the industry standard.

As influential as it's been, the quad rail fore-end may be waning in popularity. Taking its place are lightweight free-floating fore-ends with removable short sections of 1913 rails. And that makes sense. Why cover the entire fore-end with rails when you only actually need them in certain areas? The result is a design that is easier to produce and that is lighter and more comfortable to handle and shoot while the modularity allows a shooter to tailor the fore-end to meet his or her needs.

While this sort of fore-end offers certain advantages over the quad, you're still basically bolting a rail section to the fore-end and then attaching an accessory to that. Why not eliminate the rail section and attach the accessory directly to the fore-end itself? Doing so would save manufacturing costs (no rail to produce), reduce weight by removing an unneeded component and eliminate the possibility of component failure because there would be no screws to loosen during firing.

I examined this possibility in an article two years ago, and in the end I identified one huge downside: the need for a new standard

I wrote: "Without a standard there would be a chaos of parts which fit this and not that. Order is good, and God created it for a reason. So a new standard will need to be developed, put into production and gain wide acceptance. While this may sound far-fetched to some, I believe this will eventually happen."

At the time, I did not know the next standard was already in the design process. Called the KeyMod, it was developed by Vltor Weapon Systems and first released through Noveske Rifleworks before being published in the public domain in July 2012.

RELATED: Bravo Company KeyMod Rail System

The KeyMod rail, which consists of keyhole-shaped slots, is most likely to replace the standard Picatinny rail.


The KeyMod consists of a keyhole-shaped slot in the surface of a fore-end. The slot features a larger diameter through-hole combined with a narrower slot. The second part of the system is the KeyMod nut, which is designed to interface with the keyhole shaped slot.

The design itself is hardly new and has been used in shelving for decades. The end result, though, is a system that allows accessories to be fitted directly to a fore-end with no need for a MIL-STD 1913 rail interface. By eliminating the rail sections and replacing them with key-shaped slots, a noticeable amount of weight is removed from the fore-end. This allows manufacturers to produce lightweight designs in this configuration. What if your accessory requires a 1913 rail? Short rail sections can also be easily attached.

A large number of manufacturers have begun producing fore-ends using the public domain KeyMod system. These include Geissele, Bravo Company, Midwest Industries, Krebs Custom and many others. (Ed. note: This list includes CMMG, whose latest model is reviewed elsewhere in this issue.)

SLR Rifleworks in particular offers great-looking units with a small tweak. Its keyholes are machined to accept all normal KeyMod accessories, plus each hole will also accept a QD sling swivel. SLR refers to it as "QMod," and it allows you to place your sling wherever you'd like on the fore-end with no accessory mount required.

After using both, I have to say I do prefer SLR Rifleworks QMod variation. Some companies, including Geissele and SLR Rifleworks, are offering fore-ends with short integral 1913 rails at the front and KeyMod slots everywhere else.

KeyMod is not the only game in town. Tech Ops International's Battle Rail, available from Rebel Arms, features a competitor to KeyMod called T-bolt. With this system, the surface of the fore-end is slotted, which provides a texturing effect, reduces weight and allows accessories to be mounted. The inside of the rail is specially contoured to work in conjunction with the narrow slots, allowing rail sections or accessories to be mounted.

No back plates or other hardware need to be inserted inside the handguard, so the position of rail sections/accessories can be adjusted easily. The design allows rail sections to be mounted at the 1:30 and 10:30 positions without interfering with the 12 o'clock rail.

While I can't see into the future to declare what system will end up the new standard, I can say traditional quad rails are on their way out. A new standard — most likely KeyMod — will surely replace it. It's constant innovation and progression such as this that makes the AR platform so versatile and popular.

What do you think is the future of the AR-15 rail attachment interface? Comment below.

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