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During my law enforcement career, I have always trained with, and been issued, a Colt M4. While serving in Iraq as an international police advisor, I was issued a select-fire M4. However, the M4 issued to me was not a Colt, nor was it from our other primary weapon supplier, FN. In qualifying with the issued M4, I found this weapon to be defective. A military armorer examined it and told me the barrel was screwed slightly crookedly into the receiver. Because of this, the rifle shot 8 inches off to the right at 25 yards. In addition, another officer’s issued M4 (of the same brand) had a barrel so bad it would not chamber a round. The same armorer had to grind down the side of the bolt face to get the round to chamber.

During my two years in Iraq, because of the low-quality, thirdrate brand, my issued M4 would jam at the most inopportune times. And by “inopportune,” I mean when lead was flying. At those times, I wished I had the Colt M4 I carried back in the States. So, when I was assigned to write about the Colt Combat Unit (CCU) Carbine, I eagerly accepted. It would be my first time to review and write about an AR-platform rifle.

In planning this review, I reflected on those “inopportune” times in Iraq when my M4 failed me. As a result, I decided to put the Colt Combat Unit Carbine through some serious testing—not just the standard velocity and accuracy testing, but environmental testing (sticking it in mud, water, etc.) to see how well it works in not-so-perfect conditions.


In 1956, Armalite entered an AR-10 prototype in the U.S. Army competition to find a replacement for the M1 Garand. It tested favorably but lost out to the Springfield Armory T44 (designated the M14). When the Army looked into the development of a .223-caliber rifle, Armalite scaled down the AR10 into the AR15 in preparation for the request.

In 1959, Armalite licensed Colt to make AR-15s; Colt promptly sold them to what is now Malaysia. In 1961, the U.S. Airforce purchased a small number of AR-15s. In 1963, the U.S. Airforce and Army bought more than 170,000 AR-15 rifles—designated as the M16. From this point on, the AR platform basically remained the same, with some changes to enhance this rifle.

The M16A1 saw considerable use in Vietnam, and “lessons learned” led to the M16A2 being adopted in 1982. The M16A4 was later adopted by the U.S. Marine Corps as the Army moved to the M4 Carbine, both seeing use in the United States armed forces in the Middle East and other regions of the world. In 2015, the Marine Corps adopted the M4 Carbine.


The CCU Carbine is a semiauto, air-cooled, direct impingement gas-operated, magazine-fed carbine. It is the first Colt to feature the new midlength gas system. This rifle has a lowprofile gas block that allows for the use of the M-LOK-capable Centurion CMR free-floated forend. I like the looks of it.

The CCU Carbine was developed with help from well-known trainers Mike Pannone, Ken Hackathorn and Daryl Holland. The CCU came with a Magpul SL buttstock and pistol grip and the MOE trigger guard—great products I have grown to appreciate.


I started by cleaning this new rifle and applying Slip 2000 Gun Lube, an excellent gun lubricant with a good reputation. I then drove to the Oklahoma City Gun Club to sight in the CCU, along with the Leupold VX-R Hog 1.25-4x20mm scope I had mounted on it.

I zeroed the Colt at 50 yards on Splatterburst Targets, which make it easier to spot your shots. I then moved back to the 100-yard line for accuracy testing.

The Leupold VX-R Hog 1.25-4x20mm with the FireDot Pig Plex reticle is my new “best friend.” With this reticle, however, the red bullseye was harder to see at 100 yards. Even so, for a combat weapon or hunting rifle, it’s a great reticle. The aggregate grouping for five shots was 1.66 inches at 100 yards, with a 15-mph cross “breeze” (in Oklahoma, 15 mph is considered a “breeze”) coming from my left rear.

I tested the velocity of each of the six brands of ammo. As always, the lighter bullets went faster than the heavier. I chose the heavier bullets for their harder hitting properties, which equates to deeper penetration of game and sheet rock walls—on which the lightest bullets have some problems (something I learned from my fellow officers at the Wichita, Kansas, police department). The fastest ammo was the Federal Premium 64-grain HI Shock SP, at an average of 2,881 fps with a 1.3-inch spread at 100 yards. The slowest, but not by much, was the Gold DOT 75-grain GDSP, at 2,505 fps with a 1.9-inch spread at 100 yards.

The CCU Magpul SL buttstocks have a receptacle for a snap-in D-ring swivel. I chose Midwest Industries’ D-ring heavy-duty, flush-mount swivel. This swivel is, indeed, heavy duty. I like the single-point sling, so the D-ring shape facilitates the working action and use of this system. This is a great product from some great people whose products are also made in the United States.


I took the CCU Carbine up to the family farm, where I can shoot and play without the fear of other people around. I can take a 1,000-meter shot and still stay well within the property. For the torture-testing and water-boarding, I would use a creek that meanders through the property. It was flowing with considerable silt and sand from recent downpours—perfect for this test. Longtime friend and former cop Dwane Binford accompanied me.

I was determined to put the CCU Carbine and Leupold scope through some hard times. There was going to be a lot of shooting, plus some fine sand, dirt and mud, in the very near future. Up to this point in getting familiar with, and testing, the Colt Combat Unit Carbine, I had fired 480 rounds with no cleaning or additional lubrication.

I put the Colt through its paces as I chronographed each of the eight different brands of ammo. As one would expect, the heaver bullets were slower than the lighter bullets. The fastest round was the Federal Premium 64-grain, at 2,881 fps; the slowest—but still damned fast— was the Gold Dot 75-grain, at 2,505 fps.

First, I had Dwane fire four 30-round mags through the CCU Carbine at a reasonably fast pace. As he burned through the ammo, the HEXMAG magazines never had a hiccup. The six mixed brands of ammo performed magnificently. Dwane fired all 120 rounds with no problems.

The M-LOK Centurion CMR forend did heat up enough to be too hot to handle at about 105 rounds. This is a concern, because firefights can exceed 120 rounds in a very short time span. The forend tested at 156.6 degrees (F). The breach tested at 173.3 degrees and the bolt at 135.8.

I then instructed Dwane to lay the CCU Carbine on a sandbar with very fine sand and dirt. I had him cover the rifle and scope to the point at which they were barely visible. I then had him pull the rifle and scope from their sandy grave and place them in the running creek filled with silt and debris. We watched the bubbles rise to the surface as the water filled up the Colt.

After about a minute, I had him remove the dripping rifle, empty out the water and gunk, and then quickly load a fresh mag of 30 mixed rounds and fire at an even faster rate than before. All rounds fired without any jams, misfires or problems. The Leupold scope took the water-boarding as if it were a daily event. It had no leaks and was as clear as mountain air.

To top all this testing, I let the CCU Carbine sit in my gun safe for 10 days without cleaning it in any way. It had dried long before I arrived back home, but no effort was made to touch it. Ten days later, I took it out of the safe and broke it down as far as I have been trained to do. I found some fine sand and dirt—but no rust. In fact, its overall appearance was about the same as when I first received this test weapon.


As a recap, out of the box, I started with cleaning and lubricant. We then fired 480 rounds; and, with no additional cleaning or lubricant, I proceeded with the test. And, what with another 120 rounds of rapid fire, being buried in fine sand and dirt, submerged in water for over a minute, rapid-firing 30 rounds and no cleaning for 10 days afterward, I found one deficiency: the heat properties of the M-LOK Centurion CMR forend. At 105 rounds of mixed 5.56×45- and .223 Remington dirtnap pills, the forend heated up to 156.6 degrees, which is too hot to handle with a bare hand.

Besides this issue, the CCU Carbine performed in a way I could absolutely count on. It is an excellent-quality firearm made by a dependable firearm company with which I have trusted my life in the past—and I would do so again. I highly recommend the Colt Combat Unit Carbine.


colt’s manufacturing company Colt Combat Unit Carbine

  • OPERATION: Semiauto, midlength; direct impingement gas
  • CALIBER: 5.56x45mm
  • BARREL: 16.1 inches, 4150 CMV, manganese phosphate finish; 1:7-inch RH twist; six grooves; chrome lined
  • RECEIVER: 7075-T6 aluminum; black hardcoat anodized; flat top
  • OVERALL LENGTH: 33–36.5 inches
  • UNLOADED WEIGHT: 6.47 pounds
  • SAFETY: Ambidextrous safety selector
  • TRIGGER TYPE: Single stage
  • GRIP: Magpul MOE SL pistol grip
  • HANDGUARD: M-LOK compatible; Picatinny top rail
  • AVAILABLE FROM: TALO Distributors (

MSRP: $1,299


SLIP 2000


Editor’s note: A version of this article first appeared in the March 2018 print issue of Gun World Magazine.