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Colt Defense Law Enforcement Carbines

With Mil-Spec design and construction, Colt's LE M4 variants are "dead nuts" accurate and extremely reliable.

July 30, 2010  |  by Nick Jacobellis - Also by this author

The Colt LE 6940

One of the main differences between the Colt LE6920 and the Colt LE6940 is the use of a one-piece rock solid upper receiver that has a monolithic rail and a free floating barrel.

In its flat top configuration, the LE6940 is also different from the LE6920 because the LE6940 features folding front and rear sights. The folding front sight is made by Colt, while the rear sight, which can be adjusted to engage targets out to 600 yards, is made by MaTech. This is the same rear sight that is used on all Colt Mil-Spec M4s that are provided to the U.S. Army.

The Colt LE6940 is chambered in 5.56mm and incorporates additional Mil-Spec features in its design. In addition, the Colt LE 6920 and the Colt LE 6940 also have a reversible selector switch. This tidbit of information is important for law enforcement agencies and individual officers who are left handed. While field testing the Colt LE 6940 I found this patrol/tactical carbine to be surprisingly lightweight and easy to carry.

I recently sighted in a sample LE6940 that Colt sent to me to evaluate for this article and found that with some minor adjustments this rifle was dead nuts accurate at 50 yards while using 55-grain Federal FMJ ammunition.

Bear in mind that I intentionally sighted this rifle in while using the folding iron sights that come standard on this carbine. A week later a friend of mine delivered consistent head shot accuracy with every round fired from the 50-yard line while using his brand new Colt LE6940 with an Aimpoint Comp M2 and an Aimpoint 3X Magnifier.

Plain Jane vs. Pimped

Even though I tend to prefer plain Jane M4s, I found myself actually favoring the LE6940 over the LE6920. And the reason for my preference is that the LE6940 is more customizable.

For starters, I can easily install a forward vertical grip and a SureFire tactical light on the LE6940's monolithic rail system. I also have enough room on the rail for a high-quality red dot with or without a 3X Magnifier. I can even turn a Colt LE6940 into a precision rifle by installing a magnified optic like a Trijicon ACOG or a Leupold scope on the rail, which is built into the one-piece upper receiver.

It is important to note that the one-piece upper receiver, which includes the rail, provides an incredibly stable platform that enables the operator of a Colt LE6940 to deliver super accurate shot placement. According to my contact at Colt, who put this in slightly more technical terms, the benefit of a monolithic rail is that "the one-piece upper receiver offers 100-percent zero retention of optics."

Mil-Spec Quality

The Colt law enforcement carbines are both built to Mil-Spec, and that means something. For an M16 or M4 to be considered 100 percent Mil-Spec, the rifle or carbine must be manufactured to certain government standards with certain high-quality parts and must routinely pass every government inspection and testing procedure dictated by the contract. In fact, only select fire M16s and M4 Carbines that are built to strict government standards can be considered Mil-Spec.

It takes 357 "gages" (testing procedures and inspections) to produce one Mil-Spec select fire Colt M4 Carbine. For example, when Colt builds Mil-Spec barrels and bolt assemblies, it proof tests the rifle barrels with 70,000 psi cartridges followed by magnetic particle inspection (MPI) testing. MPI testing checks for any breakdown in metallurgy, any flaws, deformities, or cracks in steel barrels or their Parkerized coating. Bear in mind that the average 5.56 M855 FMJ round of ammunition has a psi factor of 52,000.

One of the things I really like about Colt law enforcement carbines is that they are manufactured to meet high standards. Quality touches on the Colt law enforcement carbines include having the chamber bored out to reliably feed 5.56 ammunition, a barrel with a 1-and-7 twist, having a properly staked gas key, and an extractor that is designed to have the proper tolerances to ensure reliable operation under extended firing conditions.

A barrel with a 1-in-7-inch twist like the type used in the LE6920 and LE6940 carbines is specifically designed to accommodate and stabilize 5.56 caliber ammunition up to 80 grains in weight. This means that you can engage targets at further distances with greater effectiveness than if you used 62-grain NATO ammunition from a 1-in-9-inch twist barrel. 

Nick Jacobellis is a medically retired U.S. Customs Agent and former police officer who was physically disabled in the line of duty while working undercover.

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Comments (17)

Displaying 1 - 17 of 17

pjjrs @ 8/2/2010 10:28 AM

I own a Colt 6920 and absolutley love it. Just finished a rifle training class put on by my department. I used my iron sights as stated in this article and they were deadly accurate. Shortly after I purchased my 6920 they came out with the 6940 and it was everything I wanted to do to my rifle. 2500 dollars later I have a 6920 that I am trying to turn into a 6940. Some of the upgrades I have added to the weapon are; gas busters tactical charging handle, ambi safety, magpul tactical trigger guard, one piece gas ring upgrade, extractor spring plus o ring, knights armrament flip up rear sight, aimpoint comp m4s optic, standard a2 front sight. I am planning on placing a free float 9in rail system on it with a flip up front sight and already have the surefire foregrip. Totally satisfied with my colt!

texas45 @ 8/6/2010 2:03 PM

Own both 6920 and 6940, both will get the job done.

Wockley6 @ 11/10/2010 8:37 PM

As a retired Army/Infantry officer, I suggest the author review the articles in the Army Times ( seach M4) starting with the 27 DEC 2007 article ( about the failure rate of the M4. There is significant discussion about the upgrading and replacement of the M4, including the ammo (stopping/penetration power). The latest article 9 NOV 2010 ( states what is currently going on for ungrading and replacement of this wpn. It should also be noted that the military has purchased the rights, 7 JUL 2009, for this wpn from Colt.

Nick Jacobellis @ 8/21/2011 11:50 AM

Response to Wockley6. While I am well aware of various complaints about reliability problems and ammunition ineffectiveness with the M4 platform in the U.S. Armed Forces, I have found M4s to be virtually flawlessly reliable during my law enforcement career and since I retired. I have tested numerous M4 variants in different conditions including in sand storms and in the desert along the U.S. Mexican Border and have been incredibly impressed by the overall reliability of 5.56 caliber carbines. If you are interested I suggest that you contact Pat Rogers a retired NYPD Sergeant and retired U.S. Marine who runs a training concern called EAG Tactical. Pat and his instructors and students have put tens of thousands of rounds through numerous M4s with incredible reliability. Pat has fired some 48,000 TROUBLE FREE rounds through his personal Bravo Company M4 with minimal maintenance and the proper lubrication. As you well known, 7.62 NATO caliber DMR platforms have been specifically adopted because 5.56 NATO compliant ammunition has generally proven to be ineffective beyond 300 yards. Even though I am a huge fan of my FN SCAR Heavy MK17S in 7.62 NATO caliber, I have absolutely no problem relying on my Bravo Co. EAG Tactical Carbine M4 (5.56), a SIG 556 Patrol SWAT Model (5.56) or a Bulgarian AK74 in 5.45x39. I have carried M4s in harms way and would have no problem doing so again. Thanks for your comments Nick Jacobellis

Daniel @ 10/18/2011 6:01 AM

The Colt 6940 is amazing! I have recently heard Colt is discontinuing the LE models. Any info on that? I have a 6940, but might be getting another one if the discontinued rumors are correct. Notice the "officer" has to quote the Army Times. As an enlisted soldier, I have relied on the M-16 through several deployments. I have trusted this weapon with my life, and wouldn't hesitate to do it again. Would a .308 been better? Yes, but the 5.56 was sufficient. The military sets up quantity over quality. Soldiers aren't always the best shot, so magazine capacity is more important that stopping power. This holds true with rifles ( 5.56 vs .308) and handguns (9mm vs .45). Anyway, just my thoughts. Great article.

george @ 9/15/2012 6:12 PM

I have and carry an Colt HBar lower with an A1 lightweight barrel upper. It is old school but in the 14 years I have owned it never once has it failed to fire. At 200 yards I can hit 1 foot by 2 foot targets off hand all day long. ...very quickly with iron sights. I have kept the rifle cleaned and the bolt well lubed with Mobile 1 synthetic 30st all these years. I am looking for another 15 years of service. God bless Colt rifle division.

Ken Webb @ 12/7/2012 10:34 AM

Any problem converting to left hand ejection? Does Colt sell this? I heave heard Stag Arms sell conversions that are mil spec too. Thanks for any response

Sid @ 6/3/2013 9:09 AM

gents, there have been many great rifles made since hte advent of the rifle. Most have their limitations. As someone that has carried an M4 in every war (US) since 1994 and has put thousands of rounds thru them I can say without hesitation that I would (and have) trust my life on the reliability of Colt M-4.

There are many reasons for the 'reliability rap", mostly crappy marksmanship. Many a cop (I'm an ex cop, fed and local) has shot at a doped up dude and still seen him walking after taking several hits. Same for the 'skinny's in Somalia and Afghanistan. The enemy in Iraq was a little 'beefier' so the round had a chance to work.

This is the same complaint that the venerable 9mm Luger often gets. Most cops and a boat load of Germans during WWII have used the 9mm very effectively.

Moral of the story, if you shoot a bad guy in someplace that counts, he'll drop, if you shoot him in the arm, ass, leg, or finger...he most likely won't...sot placement trumps BS anyday!

Patriot @ 6/9/2013 5:11 AM

The Colt LE9640 can be extremely accurate with careful ammo selection. My best 100 yard group with this rifle is .430. Less than .5 inch! This was accomplished with a Burris 4.5 X 14. The handload consisted of a 52 grain Sierra HPBT match, 24.9 grain of AR Comp, Winchester case and Remington 7 1/2 primer. I lightly stoned the trigger engagement surfaces and added the JP Enterprises reduced power spring kit for a much smother and lighter pull. The gun is capable of accuracy equal to some of the much more expensive match grade rifles.

RPK @ 7/14/2013 7:42 PM

I own a Colt LE6920, Colt LE6920 SOCOM and a Bushmaster M4A2. All three are reliable platforms for the 5.56 round. All three have a NATO 5.56 stamp on the barrel. BUT, only the two Colt's have a 1/7 barrel twist. The Bushmaster is a 1/9 twist. The Colt's can handle up to a 77 grain round. Normally, a 62 grain round is preferred. But, in the heat of battle, a 55 grain round will do the job. What is my point you ask? Depends on the purpose the shooter has in mind when the weapons platform is selected for purchase. You can put all the add-ons attached to the weapon as desired, but if the basic functioning of the weapon is sub-standard, you have a fancy looking paperweight. I spent over 20 years in the armed forces trusting my life to a Colt. As a retiree/civilian, I still make that a conscience decision. But, if the Bushmaster is the first M4 I grab to defend my life or that of my family, I am confident our lives are in trustworthy hands.

deebs @ 10/19/2013 1:44 AM

Just put together a frankengun, colt m4 style upper, on a DELTON lower with BCM lpk, ,bcm H2 buffer and tube,mag pul moe furniture. My M4 gery runs smooth and when I "focus" I get 1.5 " groups @ 100 yds.(with a decent scope probably could do better). What I've noticed are the 100% Colt snobs at the local range. One such lout looked at lowers DTI symbol and his response was, "cheap junk, you shoulda bought Colt".....really?

Michael @ 9/11/2014 9:31 AM

Le6920 Le6920 socom I have them both.Accurate reliable great weapons,but my Adams Arms and Bushmaster 14.5 upper cmmg lower are just as reliable and accurate.Im rebarreling my Colts with 14.5 inch barrels and while theyre down my other rifles are my go to weapons.I trust them as much as my Colts unless Im going to war.

Larry @ 12/27/2014 4:15 PM

Just purchased a Colt LE6920 AR15 M4 Carbine 5.56mm, 16" Barrel, 1 In 7 Twist, 1 Magazine. I'm 56 and for now will be a paper shooter. Later maybe work on more distance plus better grouping on paper. Now the quandry. Red dot vs distance scope. So many choices. I have a good bare Tra storm with light for home defense. AR too powerful for that.

Please suggest what type site system to get. Thanks.

Pops45 @ 1/15/2016 5:59 PM

I have 2 Colts, an old SP1 and a LE6920. But I'm not a Colt snob. Especially after owning a Colt 2000 All Anerican for a short time lol. I also have a DelTon Sporter, and a few frankenguns. All shoot well. The Delton originally came with a bolt carrier that wasn't milled quite right. MagPul mags would not lock in, but GI mags would fit fine. The two grooves along the bolt carrier were not milled deep enough, and wouldn't accommodate the slightly thick Pmag feed lips. Delton agreed and replaced my carrier right away. Great service! Rifle shoots fine. Although I prefer chrome lined barrels, chromemoly steel is fine if you take care of it. The Delton Sporter also has a thinner profile barrel, but for me, this made for a real light rifle that carried well on long hikes.

kevin curry @ 8/31/2016 7:09 PM

How did that stolen airplane, US custom stupidity, in AZ thing work out for you nick? Just wondering

JK @ 11/17/2016 12:31 PM

I've had around 5000 flawless rounds through my 6920. Tac shooting classes, 3 gun comp or just shooting for fun, shooting very dirty (just keep the bolt lubed) my 6920 has been nothing short of excellent. Wockley6's comments smell of the old "M16 was junk in Vietnam" argument: irrelevant, old, and most likely the bias comes from the same era. A lot has changed in 60 years with the AR platform being one of them.

The M4 has proven to be rock solid which is precisely why SF, SFOD-D, MARSOC, Larry Vickers, Pat McNamara, Travis Haley and many other current and past Tier 1 guys run it. This even considering the availability of "better" piston-driven platforms like the SCAR or HK416. Why? Because the M4 just works with INHERENT accuracy and lightweight design that the SCAR and HK416 simply don't have.

Also, the Crane o-ring isn't necessary 99% of the time. I DO run em' in my BCG but my brass has beat the crap out of my deflector (over-ejecting).

Nick @ 3/14/2017 11:19 PM

You lost me in the article when you said you refused to take the Steyr AUG and kept your colt... Lol
The AUG is my favourite rifle. A piston system that prevents fouling inherent with direct gas ARs, full length rifle barrel in a subgun sized package which not only keeps your range and accuracy solid but keeps muzzle velocity higher then a standard carbine which helps add to a 5.56 round affect on a target.
I love the 50-50 balance on the AUG which really helps with aiming fatigue, the quick change barrel is cool, the newer A3 versions have decent railspace, and hell even their propriety mags are amazing.. Sorry Steyr fanboy rant but I just had to. I'm LE& Army NG and I always have running debates with my buddy who is in my department and a former marine.. I argue on behalf of the piston system and he argues on behalf of the direct gas lol.

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