One of the better features of the AR-15 system is its modularity. By changing upper receivers, the user is able to switch from a short-barreled carbine for use in confined spaces to an intermediate-range precision rifle. Despite this versatility, the gun was designed around the 5.56mm NATO cartridge, which brought its own set of constraints in terms of case-head diameter and length—if you wanted anything other than a .223-based round, it still had to fit inside the magazine well and bolt head. In recent years, this resulted in a slew of innovative solutions such as rebated case heads (like the .50 Beowulf’s) and wildcat cartridges (such as the 300 AAC Blackout) based on the original .223 case. If you needed to go larger still, then you had to step up to an AR-10-based rifle and a .308–based cartridge, which not only added bulk and weight but also severely limited your choice of upper receivers, negating much of the system’s versatility.
Imagine, then, being able to fire any cartridge within the .308 and .223 cartridge families by simply swapping uppers. This would potentially range from the .300 WSM and its associated wildcat cartridges all the way to the .17 Rem, with about 20 stops along the way. It is this kind of extreme adaptability that is at the heart of the new Colt LE901 rifle.

When it was unveiled at a writers event at Gunsite in late 2010, the 901 was still in development, and while we all got to send a few rounds downrange through the 7.62mm NATO variant, no one was permitted to strip the rifle. The few that later escaped to trade shows were zip-tied shut. Despite this, the gun generated so much interest that the factory currently has a one-year backorder on the basic model. Not only does the 901 offer a quantum leap in versatility, but it also adds significant ergonomic benefits, such as ambidextrous controls.

Gun Details
When you first encounter the LE901, you’ll sense its solidity, like the gun was carved from a single piece of aluminum. There’s a very good reason for this impression: The upper receiver is indeed hogged out of a one-piece forging, which loses in the CNC machine something like 70 percent of its mass that is turned into chips and washed away in a blast of cutting fluid. While this method of production is time-consuming and expensive, it produces an upper receiver that is incredibly strong and rigid, with no joint between the upper and the free-floated tube or rail system. You could literally pound nails with this upper—it has the heft and rigidity to shrug off any amount of abuse. The LE901’s upper receiver features a full-length Picatinny top rail and rail sections at the 3, 6 and 9 o’clock positions. The bottom rail is removable for access to the barrel nut by means of a quick-release button. Both the upper and lower receivers have a Type III anodized finish, and other options such as film-dipping and Cerakote are in the works.

The carbine comes standard with a 16-inch, button-rifled, chrome-lined barrel that has a 1-in-12-inch twist rate and is optimized around the 147-grain NATO ball round. I would have preferred to have seen a 1-in-10-inch twist rate on the base model, but Colt staff had canvassed their potential customers and found the 1-in-12 was the most popular option. The barrel is equipped with a mid-length gas system, an A2 sight tower and a Vortex flash suppressor. I predict a small cottage industry will spring up in the next few months to produce custom barrels for this rifle, as the Hartford plant struggles to keep up with high demand for the first LE901 variant. I’ll be standing in line with my credit card at the ready for a 22-inch mid-weight tube in .260 Rem.

The lower receiver is a departure from the familiar AR-10 pattern, in that the front takedown pin is shifted about an inch south from its familiar position at the front of the magazine well, which itself is cut at a 45-degree angle. This innovation allows the use of a patented magazine-well adapter cassette, which permits the user to drop in any mil-spec 5.56mm upper receiver without modifying the weapon. Simply attach the insert to the upper using the captured, shortened, headless takedown pin and drop the assembly into the 901 lower. At this point, the user can stuff a 5.56mm magazine into the mag well, yank the charging handle and commence firing. Colt supplies a standard H2, 5.56mm carbine buffer and spring to complete the conversion process. However, during range-testing we had no problems running the heavier AR-10 recoil-system components with 5.56mm ammunition. In conversation with Colt employees, we discovered that the lighter buffer and spring are really only needed in full-auto versions.

Both sides of the lower receiver have their own magazine release and bolt catch, accessible with the index finger of the firing hand—left-handed shooters can rejoice. One control that is not ambidextrous from the factory is the safety lever, and as a righty who has experimented with AR ambidextrous controls, I have to say that this is not a detrimental choice. I’ve always found right-side safeties to get in the way of the base of the index finger and to be generally annoying when running the gun. With the amount of aftermarket safeties available, this is an easy and inexpensive part to add if you so choose. About the only area of the lower receiver that has room for improvement is the trigger, which is a typical mil-spec AR unit. On a rifle of this quality, I consider a decent trigger to be nonnegotiable, and while the one fitted to the test rifle was a pretty decent example of the breed, there are so many creepy, heavy, gritty government triggers out there that I guarantee not all of the LE901s leaving the factory will be so blessed. One of Bill Geissele’s excellent two-stage SSA triggers would be an obvious choice to improve the practical accuracy of the 901.

Range Time
At the range, we went through the usual preflight checks, loaded up magazines and mounted optics. The 20-round polymer Magpul magazines supplied with the rifle are designed specifically for the LE901 and feature lugs molded into the magazine body to prevent over-insertion. This is indicative of the amount of thought and testing that went into the gun. While standard DPMS-pattern magazines will also fit, the addition of overtravel stops are a welcome improvement and worthwhile upgrade. (Note that 901 magazines may or may not fit other manufacturer’s weapons due to differences in magazine-well geometry.) To test accuracy, the gun was fitted with a Leupold Mk 4 scope featuring a 34mm tube and first focal plane reticle. Its excellent glass and true 1x magnification on the low end, coupled with mil/mil turrets, make for an excellent intermediate-range sighting system, well matched to the capabilities of the 7.62mm round. On low-power, it can be used like a red-dot and shot with both eyes open to engage opportunity targets, while its ability to dial up to 6x enables the shooter to accurately engage torso-sized targets out to the limits of the cartridge.

Foregoing the usual sight-in procedure, I stuffed the magazine with handloaded Nosler 155-grain JHP match ammunition (CCI Benchrest primer, Nosler brass, 45.5-grain H4895), picked a 4-inch-diameter rock on the backstop at 328 yards and fired the first shot. Using the Leupold Mk 4’s mil reticle, I measured the distance from my target to the bullet’s impact, dialed in a correction and sent another round downrange. After tweaking the locking turrets one more time, the rock disappeared in a cloud of dust on the third round—very gratifying. Additional shots proved the carbine’s accuracy potential and left me in no doubt that this gun could be a very capable designated marksman rifle.

Dialing down the scope, we ran the LE901 through a series of barricade and off-hand drills at ranges from 7 to 100 yards, then swapped in a 16-inch 5.56mm upper and repeated the procedure. It should come as no surprise that the 5.56mm upper allowed for split times that were considerably less than those of the larger caliber upper, but what was surprising was that target transitions were almost identical. The LE901 is about 8 ounces heavier than a similar AR-15 lower receiver, but that additional mass is centered between the shooter’s hands, so it feels like a whole lot less. During the 200-round range session I experienced only one stoppage. This was caused when a primer backed out of an American Eagle case and was rammed into the barrel extension, preventing the bolt from locking up. I consider this an ammunition rather than a weapon failure, and it required spearing with the tip of my knife to dislodge.

Final Thoughts
The Colt LE901-16P provides the shooter with a weapon system that has the potential to fit the widest number of roles by switching out upper receivers, which should have special appeal to LE agencies with a sniper program. An officer could potentially use an SBR 5.56mm upper for building entry and quickly swap in the 7.62mm version when tasked with overwatch or countersniper duties, providing maximum versatility from one lower receiver. For more information, visit coltsmfg.com or call 800-962-2658.