7/25/11 - Vltor Weapon Systems released the Data Package for their KeyMod (KM) System today. The KeyMod System is a new rail interface system developed by Vltor. Rather than keep it proprietary, Vltor is putting the Data Package in the public domain for anyone to use. The KM System was introduced at the 2012 SHOT Show, with Noveske Rifleworks being the first to offer a handguard with the KM system, in their NSR Rail.

Back in December, 2011, Eric shared with me the first drawings of his planned KeyMod system. Since then, I've followed the develpment of the system with interest and impatience. The KeyMod system uses keyhole-shaped holes in the handguard, with bevels on the back, to automatically center direct-attach accessories as they are installed. All access is from the outside of the rail with captured screws. Besides the handguard, Vltor and Noveske will be offering accessories for the KM system. 1913 rails can also be attached to the KM handguards for use with any Picatinny-compatible accessories.

The press release from Eric Kincel is as follows:

The Vltor VIS KM (KeyMod) is currently in the works - shown below are renderings of the planned offerings. Vltor will be offering the same four lengths as before (7, 9, 10 and 12-inch). Relevant to suppressor users, the internal dimension of the VIS KM is 1.400" (without the heat shield) and 1.125" with heat shield. The outside diameter is 1.725 inches. The total height (from the top of the Picatinny Rail to the bottom handguard) is 2.125".

Noveske will be getting the first quantity of VIS KMs, followed by the release to the general public, under the Vltor banner. The Noveske NSR rail is a one-piece handguard system for the AR-15, and differs in size and shape from the VIS KM.

Noveske NSR rail

The Data Package drawings are shown below. Download the .pdf file here (you can open it or right click and 'save as'). Manufacturers are free to use the Data Package to design handguards or associated accessories for the KM system without needing consent from Vltor, or paying any royalty fees etc.

Sheet1

Sheet2

Sheet3

Sheet4

The prototype VIS KMs are illustrated below, along with equivalent VIS uppers to show the difference in weight. Each VIS KM version averages a 6 ounce weight reduction over the original VIS system. More information will be added as it becomes available.

10/6/12 - The NSR Handguard from Noveske Rifle Works is the first handguard to offer the KeyMod (KM) System. The KM System is a collaboration between Vltor Weapon Systems and Noveske Rifleworks. The KM System offers a mounting platform for a variety of accessories and components. In July, Vltor Weapon Systems released the Data Package for the Keymod (KM) system so any manufacturer can adopt it or make accessories for it, royalty-free.

General Description - The idea behind the KeyMod system is to get rid of the need for a secondary interface (rail) for attaching accessories. Without side and bottom rails, the NSR handguard achieves Noveske's goal of being one of the lightest and narrowest free floating forend options for the AR15/M16 family of weapons. The outer width of the NSR handguard before accessories have been installed is only 1.48". Inside width is 1.325". Height from the top of the rail to the bottom is 1.95". The NSR handguard is available for sale as standard equipment on Noveske's rifles and upper assemblies, as well as a separate component.

The NSR-13.5 handguard pictured here is 13.5" long. The NSR is available in 7", 9", 11", 13.5", and 16.7" lengths. All of them share the following features:

• Hard coat anodized aluminum - currently available in black only
• Ultra light and robust
• 1913 continuous top rail
• Steel barrel nut
• Includes: Handguard, barrel nut, mounting screws, T25 wrench and instructions
• Not included: 1 1/16" Crowfoot wrench or medium strength loctite

The steel barrel nut weighs 3.1 oz and the NSR-13.5 handguard weighs 7.9 oz. The weights of the other length handguards are listed on Noveske's website.

Handguard - The handguard is very narrow, and even my small hand can grab around it completely. The NSR has a standard 1913 rail on top, at the same level as the receiver flat top. The top rib is ventilated on bith sides with slots. At 3, 6, and 9 o'clock, the NSR has rows of the KeyMod 'keyholes'. At the 10:30 and 1:30 positions, there are rows of long slots. At 4:30 and 7:30 are rows of shorter slots, and holes in between the slots. At the rear of the handguard are holes for the mounting screws, that secure it to the barrel nut.

Barrel nut - The steel barrel nut is cylindrical and is actually reversible; it has internal threads on both ends. The threads are timed 15° from one another so that the installer has a total of 24 timing positions with the upper receiver. The two rows of threaded holes around the outside of the barrel nut are what need to be timed such that the handguard is aligned properly with the flat top rail. The barrel nut has flats between the rows of holes for a 1-1/16" crowfoot wrench.

NSR-13.5 and barrel nut

End views

Installation - You have to start off with the gas block removed, obviously, to install the NSR barrel nut. The barrel nut is slid over the barrel, and the barrel extension inserted into the receiver. Noveske recommends putting moly grease on the receiver threads and front of the barrel extension. The barrel nut is then installed hand-tight, noting the position of the handguard mounting screw holes. A row of handguard screw holes needs to be just past the 12 o'clock position when hand tight. Try flipping the barrel nut over to get the best alignment. The barrel nut is then torqued to 40 ft-lbs. It's then loosened then torqued again, twice. The use of a receiver block is required for this process.

Moly grease is re-applied, and the barrel nut torqued down to 40 ft-lbs. The barrel nut must be aligned with the threaded holes at 12, 3, 6 and 9 o'clock. To achieve this alignment, the barrel nut can be torqued to a maximum of 80 ft-lbs, to align to the next screw hole if needed. If alignment cannot be achieved, flip the barrel nut over and start the process of torquing, loosening and re-torquing over again.

The tricky part, in my case, was finding a wrench to fit the barrel nut. You can use either a 1-1/16" or 27mm crowfoot, but it must be 0.5" thick or less, as the width of the flats on the barrel is only 0.5". I had to take a dremel to grind down the Sunex 27mm crowfoot you see below. It was a pain in the butt, but I already had it, and didn't want to spend the cash on a Snap-on. Took me about 20 minutes of hand grinding with a dremel. Other folks have had the same issues finding a crowfoot that's narrow enough. An adjustable wrench is too thick (I tried that too). I think that the width of the flat could have been increased to about .65" without any consquence (that I'm aware of) - I'd like to see something like that happen. The two rows of holes would just be a little further apart, and the barrel nut a bit longer.

The other hiccup I ran into was my gas block. I wanted to retain the pinned gas block that came on my M4 barrel, so I cut it down. Cut the fixed sight off, as well as the bayonet lug and swivel. Went to slide the handguard over it, and it wouldn't fit. I had to shape it to emulate that of a low profile gas block (more dremel work). I finished it with a few passes of high-temp engine paint I had sitting around. It didn't have to be pretty since it's barely visible through the holes in the handguard. Unless you want to spend time modifying a fixed FSB, I'd recommend just getting a low profile gas block like a Vltor.

27mm crowfoot

Modified to fit

Barrel nut about to be installed

Using a receiver block

Gas block installed

Gas block modified

Once I ensured that I had good clearance on all sides of the gas block, and the inside of the handguard, I installed the handguard onto the barrel nut. When the screws are installed, but not tightened down, there's a tiny bit of rotational play that you have to work with, if the barrel nut isn't perfectly aligned to 12 o'clock. I used an old Trijicon ACOG mount to clamp both the receiver top rail and the handguard, so that the handguard top rail was aligned with the receiver rail. I then installed the six screws with blue loctite and tightened them up per the instructions.

Bottom holes lined up

Using a rail guide

Done!

KeyMod Interface - In the previous article above, where the drawings for the KeyMod system were released by Vltor, the description of how the system works may not have been completely clear. The photos of the accessories below will help illustrate the system.

Paraphrased from the Noveske website: The KeyMod system offers a mounting platform for a variety of (future) accessories and components. The KeyMod self-contained components/mounting hardware index and V-block onto the platform, achieving a secured and accurate hold to the system, while separate lugs take the recoil force off the fasteners. The pass through attachment method eliminates the need for loose screws and backing plates that can easily be lost, or difficult to install. Another advantage of the KeyMod system over the 1913 system is the direct attach eliminates the need for the 1913 system as a "middle Man" thereby reducing weight and accessory off-set from the center of the handguard.

The two accessories below illustrate how the KeyMod system works. On the QD sling mount, there are two mounting screws, each with a captured accessory nut. The nut is flat on two sides, which prevents it from rotating. The nut has tapers which match the chamfer on the back of the keyholes in the handguard. This makes them self-centering, and prevents any up or downward movement of the accessory on the rail. To install the sling mount, the screws are loosened and the nuts passed through the rear of the keyholes. The mount is then slid forward, and a small counter-recoil lug on the front hooks into the keyhole in front of the mount, preventing it from moving backwards. The screws are then tightened. The QD sling swivel mount is rotation limited so that the swivel doesn't rotate.

The 5-slot KeyMod 1913 Section utilizes a different method for counter recoil. Instead of the small lug on the front, it has a round lug behind the forward accessory nut. This lug fits into the round part of the keyhole and prevents any forward or aft movement of the rail section.

Chamfer on back of keyhole

QD sling swivel mount

Sling mount installed

Rail section

Rail section installed

Noveske offers Polymer Panel sets for the NSR in black, foliage green and flat dark earth (FDE). They're very low profile and have a molded texture for a secure grip. Each set includes one long panel which covers 7 KeyMod slots, four short panels which cover one slot each, one locking panel, one rear handstop (the longer one) and a front handstop (the shorter one). Both handstops lock by themselves. If you look closely at the panels, you'll see that only the locking panels have a small T-slit on the outside, and a semi-circle on the back which engages the keyhole. The panels are installed by inserting the keyhole-shaped lugs on the back into the keyhole, and sliding the panels forward. A locking panel is required to keep them from sliding backwards. Removing the locking panels is a bit of a pain, as a thin instrument or hook needs to lift up on the split tabs to disengage the semi-circular locking lug while pushing rearwards on the panel.

If you want to cover the bottom and two sides of the handguard, you'll need two sets.

Black panel set

Foliage green

Flat dark earth

Back of the panels

Orientation on handguard

Notes/Observations - The most obvious attribute to anyone who picks up an NSR-equipped rifle is how narrow/slim the handguard is. Granted, the lack of rails would make any handguard slimmer, but the NSR might be the narrowest one so far, in the tubular/slick handguard category. Yes, there are other tubular/slick rails out on the market, but the main difference is that the KeyMod system on the NSR serve both as vent holes and as a mounting system. Other rails with holes and slots can make use of the excellent Mount 'n' Slot accessories from Impact Weapon Components, but the backing plates can sometimes be a bit of a pain to get in place, and aren't as conducive to quick on/off as the KeyMod. As time goes on, we're going to see more and more KeyMod-compatible mounts and accessories hit the market. It just makes a lot of sense.

The other thing that people notice is how light it is (in this particular configuration). I've configured the rifle above with a standard M4 barrel with carbine gas system. The back up sights are from a HK MP7. Instead mounting the front flip-up sight all the way at the end of the handguard, I chose to mount the front flip-up sight as shown below to free up the front of the top rail on the handguard for accessories (such as the INFORCE WML pictured). Mounted at 12 o'clock, the WML button is perfectly placed for thumb activation. Yes, I give up some sight radius, but it's no worse that an M4 with fixed front sight base, as I have the front sight mounted just above the gas block. This is best done with a rifle-length handguard, as a carbine or midlength would not have enough space to do so.

The short section of rail is there for throwing a bipod on, which I only use when zeroing the weapon; then I take it off for regular use. The NSR panels are pretty comfortable and grippy, but I'd love to see TangoDown come out with some of their SCAR panels for the NSR, as I really like that texture. I also thought that the NSR hand stop could be rounded a little more on the edges, or shaped more like the IWC or Gear Sector hand stops to be more ergonomic.

At the range, the NSR felt feather light, and very nimble. I was curious about how hot the handguard would get, as it's narrow and doesn't have a heat shield, so I did a lot of shooting without gloves on. I was surprised to find that it didn't heat up as much as I expected it would. Even after doing three full mag dumps in a row. The extensive ventilation probably has a lot to do with it, plus the aluminum isn't very thick such that it retains much heat. The small diameter of the handguard makes it easy to wrap my support hand around, but I might go to a short vertical grip when they become available. I find them more comfortable than handstops in general, for most positions. I really like the KeyMod system and think that it has a lot of potential; and really look forward to seeing more accessories and mounts become available for it.