Military Watches
Find us on Facebook


Printer Friendly VersionPrinter Friendly VersionSend to a FriendSend to a Friend

When Mr. L. James Sullivan designed a smaller version of Eugene Stoner’s AR-10 rifle to start the AR-15 on its long, infamous life, the M1913 rail (informally referred to as the “Picatinny” rail) did not exist. While firearms designed after 1991 have had the potential of being conceived with the M1913 rail system in mind, the AR-15, like a number of 20th century rifles, had to play catch-up. Where some other weapons truly required a great imagination to be adapted to the M1913 rail, it was almost as if the AR-15 was waiting for it all the time.


Having been kept abreast of Mr. Richard Swan’s quest to design a universal rail system for the U.S. military since the late 1980s, I received one of his first A.R.M.S. “Swan Rails” in early 1992. The carrying handle of a standard AR-15 upper receiver was machined off and replaced by a full-length dovetail. The new rail was permanently attached to the dovetail to create the first AR-15 flattop upper receiver. As soon as I saw it I knew it would revolutionize mounting systems…I just didn’t know to what extent. As they say, the rest is history, with Swan’s flattop rail having been adopted by Canada, as well as Colt’s Manufacturing. The US military also adopted the rail as the M1913, where it became a standard feature in the design of the M4A1 carbine and the M16A4 rifle for the U.S. Marine Corps and U.S. Army, respectively. However, this was just the beginning.


Although Dick Swan envisioned his rail to be used for every conceivable mounting solution for a weapon, not all of the firearms industry was quick to understand the ramifications or the application. The top rail soon evolved into an extended top rail and then side rails and a bottom rail, and the “quad-rail” was born. With this system, not only could optics be mounted on the top rail with a true return to zero, but also other sighting aids, such as lasers, could be mounted to any of the four rails. This was especially important where none of the rails touched the barrel, commonly referred to as free-floating the barrel.


Free-floating the barrel accomplishes a number of improvements in a rifle. It eliminates interference with the barrel resulting from contact with the handguards or stock, and prevents direct heat transfer from the barrel to the handguard. The former is detrimental to accuracy, and excessive heat to the handguard renders it no longer a hand GUARD. This is especially apparent when rapid or full automatic fire is used.


Today most makers of quad-rail fore end systems offer free-float rail systems even if they also offer such systems that contact the barrel. I must stress that for normal application, handguards of any kind that contact the barrel should not be detrimental to general usable accuracy of say 2 MOA on a cold barrel.


What’s more, systems that contact the barrel will normally not become too hot to handle using semi-automatic fire. However, systems that contact the barrel may not be suitable for mounting optics or lasers that are intended to be used as sighting devices, this because of possible shift from barrel heat. The bottom line is that, for top accuracy with all things being equal, a free-float barrel should always out-shoot a barrel that is not free floating; but all quad-rail systems are not equal.


Some quad-rail handguard systems, whether they be free floating or not, may not line up with the main rail on the flattop receiver, and this rail is always the master rail. Such add-on rails may not be of the same height as the receiver rail and may not be straight with it, i.e., they may angle left or right, and they may also be canted. Canting can be corrected during installation by using a master clamp that aligns both rails while the quad-rail is being tightened. I use such a fix when installing any quad-rail that is independent of the receiver rail, and such a gauge is

used by Knight Armament Company when mounting its URX rail, which results in an ideal installation.


All One Piece!

However, several makers have what many agree is an even better, although more expensive way, that is called a monolithic rail system. A monolithic handguard rail system is one that is integral with the upper receiver, whether it starts life as a single extrusion or forging or is permanently joined during manufacture. The result is a continuous top (and side) rail system that can never move and that is as perfect a straight line as can be made. Such is the rail system used on the new Colt Model 6940.


Developed for the US Special Operations Command’s (USSOCOM) Special Operations Combat Assault Rifle (SCAR) Program, the monolithic quad-rail system used on the Colt Model LE 6940 leaves the barrel totally free floating and also comes with a quick-detachable bottom (6 o’clock) rail. Removing this bottom rail not only allows access for cleaning out mud and other debris but also allows the rifle to use a standard M203 40mm grenade launcher that is popular in both military and law enforcement applications, the latter for accurate placement of chemical agents.


Because the Colt Model LE 6940’s bottom rail locks tightly in place, it is capable of return-to-zero for mounting virtually any sighting device, in particular a laser. Of course, the rifle’s side and top rails are permanently fixed for rigid mounting. To remove the Colt’s bottom rail, the Q.D. sling mount must first be removed from the front of the handguard (it can be attached from either side). The bullet point of a 5.56x45mm cartridge or similar tool is then used to depress a detent in the rear of the bottom rail, and the rail is then moved a short distance forward where its interrupted rail will allow it to fall free from the monolithic upper portion. Cleaning can be accomplished or an M203 40x46mm grenade launcher can be mounted, leaving the bottom rail removed. Otherwise, to replace the rail, it is returned, slid to the rear and locked by again depressing the detent.


A Barrel-mounted Front Sight

As is generally preferred, the Model LE 6940’s front sight is mounted on the barrel instead of the top rail. The sight is of the flip-up type controlled by a strong detent and uses a standard protected post that is adjusted for elevation in the same manner as the standard AR-15 front sight. This barrel-mounted system not only extends the sight radius to increase accuracy potential but also reduces the margin for error in using the gun at a distance different from that for which the rifle was sighted in. However, barrel-mounted front sights can become hot after sustained fire, causing a

problem in manipulating the sight using the bare hand.


The Colt’s rear sight is adjustable for windage and consists of a flip-up aperture that is fast elevation click-adjustable out to 600 yards by a rotating lever on the left side. This aperture also uses a heavy detent to hold it in the up or down position, the latter allowing easy mounting of high power optics for proper eye relief and cheek-weld.


Like any Colt flattop AR rifle, the Model LE 6940 is perfectly suited to mounting any reflex sight. Additionally, with its continuous monolithic top rail, it can handle any combination of magnifiers, as well as night vision devices that mount to the rear or in front of optical sights, all this while keeping them in perfect alignment.


Aside from the above features, the Colt Model LE 6940 is essentially a straight M4 configuration. Included is a buttstock that is adjustable for length of pull. It is not a retractable stock, as has been widely suggested, but one that allows a choice of length of pull for various builds as well as different layers of clothing. After all, users of rifles should be allowed to be in comfort just like having an adjustable seat in a vehicle.


Initially, I left the Model LE 6940 pretty much as it came out of the box, adding only a few after market accessories including a Trijicon 4x32mm ACOG used to test 100-yard accuracy. After all, the LE 6940 comes from Colt essentially ready for duty. However, I then decided to go further. The Model LE 6940 lends itself to the use of nearly all the myriad of aftermarket accessories now offered for the AR platform. The bad news is that not all of them are worth your time or money. With this in mind, I arbitrarily outfitted my sample Colt LE 6940 with a number of aftermarket components that have proven themselves to be of the highest quality and the best design with input from, not “couch commandos,” but true operators. More to the point, they are among such components that I prefer for a rifle of this size, and most of them were in flat dark earth. Let’s take a look.


The Most Prolific Weapon Stabilization System in the World

Starting at the handguard, I covered the LE 6940’s top rail with a Low Profile rail cover from Falcon Industries and the side and bottom rails with pebble-grain rail covers from TangoDown. Both companies make both kinds of covers in black, OD green and flat dark earth. I chose flat dark earth for the accessories I put on the rifle and this included a GripPod in this color that was recently adopted by the DEA for use along the U.S. southern border.


The most prolific weapon stabilization system in the world, the Grip-Pod has been universally adopted by the U.S. Army and the United States Marine Corps for every M16 in the system, as well as special units within the U.S. Navy and Air Force, and the entire British Army. Additionally, Delta Force, the FBI/HRT, ICE and hundreds of law enforcement agencies have adopted the GripPod. Now, a M1913 rail dual light mount is available for the Grip-Pod. On one side of this rail I mounted a SureFire G2 Light in a VLTOR 1-inch Ring Mount, which places the light ideally for operation by the support thumb. On the left rail I mounted a LAZ/TAC bright red laser from Laser Devices, giving me the option of light, laser or both, and this small laser is good to 450m in low light. The GripPod is available from Brownells, Mounting Solutions Plus, Brigade Quartermasters, RSR and others. For a superior pistol grip, I selected Falcon Industries’ ERGO pistol grip in flat dark earth with its rubbery texture, and to the rear I replaced the standard adjustable buttstock with the EMOD Stock from VLTOR. Instantly adjustable for length of pull, the EMOD stock has two spare battery tubes that blend into the stock, as well as a rubber non-slip butt pad, small parts storage and instant sling mount.


The Weak Link – the Magazine

Until a better magazine comes along (if one ever does), I’ll be using the Magpul P-MAG, the finest, most reliable and most indestructible M16 magazine ever, in my opinion. Having easily passed the 1/2-ton Chevy pickup test – TWICE – the P-MAG is the toughest magazine I’ve ever seen. It comes with or without a window in black, OD green and flat dark earth. I used the latter in my flat dark earth dressed Colt Model LE 6940. By the way, if you own a foreign 5.56x45mm NATO rifle, you’ll want the Magpul E-MAG made for the slightly narrower magazine wells of these foreign rifles.


For an optical sight in flat dark earth, I selected the Eotech Model 553 with its integral dual A.R.M.S. ThrowLever mounting system that  has been adopted by the U.S. military.The favorite of many in the military, this Eotech comes standard with its illuminated red circle/crosshair  reticle with built-in night vision settings and can be instantly removed and replaced with no loss of zero.


Finally, to carry all this around, I selected a Vickers Tactical Sling from Blue Force Gear. A 2-point sling that works like a 3-point sling, the Vickers sling comes in a variety of styles as well as the above three popular colors. It also has an instant extension system that allows transitioning, as well the ability to get out of the sling instantly if need be. If you prefer a different type of carry, Blue Force Gear has it too.


Down Range

With a typical AR-15/M16 trigger pull, the Model LE 6940 can’t be expected to produce match accuracy… Or can it? Shooting the LE 6940 from the bench with the best quality .223 Remington caliber ammunition behind a Trijicon 4x32mm ACOG scope produced 5-shot groups averaging less than 2 inches at 100 yards. Even with M193 ball the rifle produced 5-shot groups of just under 2 inches, although M855 “green tip” produced 5-shot groups of over 3 inches.


With the upper receiver component assembled onto a selective fire lower, the Colt digested a variety of 5.56x45mm (.223) ammunition at the rate of about 750 rounds per minute. There were no malfunctions of any kind during all our firing and all operations were smooth and positive. Yes, Colt offers a selective fire version of the Model LE 6940 for law enforcement and military sales.


If you’re looking for the genuine article made to the highest specifications, now you can have it with a totally

rigid monolithic rail handguard system and fully adjustable factory flip-up sights right from Colt’s Manufacturing Co., LLC, PO Box 1868, Dept. SOF, Hartford, CT 06144, (800) 962-COLT (coltsmfg.com). To keep your Colt LE 6940 and the rest of your guns, JOIN the NRA…DO IT NOW!


Other Contacts:


230 West Center St., Dept. SOF

West Bridgewater, MA 02379

(508) 584-7816



Brigade Quartermasters, Ltd.

1025 Cobb International Dr., Dept. SOF

Kennesaw, GA 30152

(770) 428-1248



200 S. Front St., Dept. SOF

Montezuma, IA 50171

(800) 741-0015



Blue Force Gear

PO Box 853, Dept. SOF

Pooler, GA 31322

(877) 430-2583



Eotech, Inc.

3610 Green Ct., Ste. 400, Dept. SOF

Ann Arbor, MI 48105

(734) 741-8808



Falcon Ind.

PO Box 1690, Dept. SOF

Edgewood, NM 87015

(877) 281-3783



Laser Devices

2 Harris Ct., Ste. A-1, Dept. SOF

Monterey, CA 93940

(800) 235-2162



Magpul Ind. Corp.

PO Box 17697, Dept. SOF

Boulder, CO 80308

(877) 462-4785



Mounting Solutions Plus

10655 SW 185 Terrace, Dept. SOF

Miami, FL 33157

(800) 428-9494



SureFire LLC

18300 Mt. Baldy Cir., Dept. SOF

Fountain Valley, CA 92708

(800) 828-8809




4720 N. La Cholla Blvd., Ste. 180, Dept. SOF

Tucson, AZ 85705

(520) 888-3376


Trijicon, Inc.

PO Box 930059

Wixom, MI 48393

(800) 338-0563



Vltor Weapon Systems

3735 N. Romero Rd., Dept. SOF

Tucson, AZ 85705

(866) 468-5867



WARNING AND DISCLAIMER: Any content in this publication, including technical data, reports of any activities, information, events and circumstances under controlled situations and under supervised control have not been tested nor approved nor were under the control of Soldier of Fortune Magazine. Reports are transmitted from independent sources to which SOF has neither supervision nor control. The data is transmitted for reporting events by the author. Soldier of Fortune Magazine, its agents, officers, consultants nor any other individual or entity reject any and all responsibility for any reporting in this publication. Any reports in this publication do not provide detail for comprehensive safety techniques, training techniques, training precautions that are absolutely essential for any covered or similar activity. The reader MUST not attempt any reported activity, technique or use of equipment based upon any reports in this publication. Comprehensive training, guidance and supervision is always necessary when engaging in any activity of which any report in this publication mentions or gives any reference to. The views of the authors do not represent the views of the Soldier of Fortune Magazine.