Colt M4 Ops .22LR AR-15 Rimfire


Colt M4 Ops .22LR AR-15 Rimfire

Now that I’m on my third .22 AR-15, a list that includes the Hk416 and S&W M&P15-22, I am learning that .22LR AR-15s are one of the best training tools around, and they pay for themselves in only a couple afternoons of high round count, especially at today’s .22LR ammo prices.

After testing and reviewing the Umarex HK416 .22LR AR, I decided I also wanted the Colt M4 Ops branded and patterned version as well for a couple reasons. First, the Colt M4 Ops is a near perfect analog training stand-in for almost any standard carbine length AR-15 on the market from both a weight and configuration perspective. Second is that once you own one of the Umarex HK or Colt .22 Rimfire ARs, all the magazines will swap back and forth, which will most likely be your biggest investment in .22LR ARs. Somehow those magazines always seem to be empty.

Umarex USA is the team which designed and developed the HK and Colt licensed line of .22LR M16 and M4 models. If you are familiar with the much touted quality of either of these .22LR rifles, then it will come as little surprise that the internals, AR style magazines, barrels, and accuracy has been duplicated in both the HK and Colt models.



Fit, Finish, and Feel

At this point, I own all the major brands of .22 ARs and I can say the Umarex Colt is very solid, well built gun with excellent fit throughout. Unlike the S&W, pretty much everything on the Colt M4 that can be made of metal is, with the exception of the rear sights. The front and rear take-down pins on the HK were aluminum; the Colt’s are steel. The HK’s front sight was plastic, but the front sight on the Colt is metal.

The finish on all the aluminum bits is of high grade anodizing, but Umarex does not specify what Type (I, II, or III) anodizing (also, the upper and lower are an unspecified type of aluminum). My assumption is that it would be tough to hit this price point with a 7075 Type III anodized receiver set when a lesser expensive aluminum and finish would work perfectly in this situation.

At 5.9lbs, the .22LR Colt M4 Ops is lighter than a typical 7-7.5lb 5.56 version. One of the things I really liked about the HK, which carries through on the Colt M4 Ops rimfire AR-15, is that there’s enough heft to make it feel real vs the uncharacteristically light S&W M&P1522 .22LR AR. Due to the weight similarity to a real AR-15, training with the Colt M4 Ops .22 rimfire AR-15 will provide a more similar feel to a standard AR. Having a gun feel right from a weight and ergonomics perspective is the right step forward for realism and training.




The Colt M4 Ops .22 rimfire AR-15 is a dead ringer for the real deal, and it is pretty close functionally as well. Not to dash hopes of bolting on an Colt M4 Ops .22 Rimfire upper onto your existing AR-15 lower, but the Colt M4 .22 rimfire AR-15 has proprietary internals and functions differently than an AR. The upper and lower receivers have been specifically designed to assure non-compatibility with standard AR receivers and trigger parts, but the stock and grip can be swapped with any standard AR parts. The aluminum guardrail can accommodate all the standard picatinny compatible accessories

The internals are also unique to Umarex, differing significantly from the standard Ceiner style AR conversions. On the outside, the trigger feels like a really nice AR trigger, but it’s drastically different internally than any standard AR. The same goes for the bolt assembly. Part of the unique internal design was to reduce jams and decrease cleaning after firing those very dirty little .22LR rounds. To do this, Umarex developed semi-sealed upper and lower receiver internals for less maintenance.

The other two goals were to maximize accuracy and reliability, which they did with a proprietary bolt design and spring which can be adjusted and tuned for more or less spring tension via a hex wrench. Unlike other .22LR AR-15 conversions, you can tune down the spring tension to even run subsonic rounds reliability. This maximizes reliability with faster or slower .22 rounds. The Umarex line does not require that you run “hot” high velocity ammo for good reliability. For most ammo, you will never have to tune the spring, but it is a great feature to be able to tune the reliability for hot or cooler velocity rounds for optimal reliability.



Like the HK model, the Colt M4 Ops features that same awesome shooting Carl Walther match grade barrel liner. Some may want to swap out the flash hider for other accessories. Sadly the flash hider has smaller non-standard threads, so expect to stick with the stock flash hider unless someone makes an adapter. Another non-functional component is the forward assist, which is there just for looks.

The fixed rear sights are standard looking, removable picatinny sights. Unlike the problems I had with the HK version, I had no issues zeroing the Colt for a 25 yards zero.


The bolt hold open catch is actuated via the thumb helper on the magazine, and it pushes up on a metal bolt hold open catch after the last shot. Unlike typical AR bolt conversions, which hold the bolt open as long as the empty magazine is in place, the bolt on the M4 .22 is held open even after the magazine is removed. The end result of these mechanics is that the magazine can drop free, which allows you to practice your reloads. But one major shortcoming is the requirement to release the bolt via pulling back on the charging handle. That’s definitely not standard manual of arms for practicing tactical reloads.

Throughout all the testing, I was very impressed with the reliability, perfect feeding, and firing of everything from standard velocity to CCI Stingers. I did have a couple failure to feeds after everything gunked up at about the 600 round mark, so plan on cleaning around that point.

The Umarex AR magazines are by far the easiest of all AR magazine types to reload, thanks to the thumb buttons on the sides of the magazines. Reloading is a pain free event, although you seem to reload a lot with this rifle, so I would encourage buying extra magazines which are available in a variety of capacities.

The Colt M4 Ops .22 rimfire AR-15 features a match grade precision barrel which delivered a .4” 25-yard group with open sights. Topping the M4 with a Nikon ProSTAFF EFR 3-9 scope delivered several .75” 50-yard groups with CCI Standard Velocity Ammo. The Umarex line of AR rifles are stunningly accurate.

Final Thoughts

I own both the HK and Colt branded Umarex rimfire ARs, and the S&W version as well, but the only reason I do is because of the bolt release capabilities of the S&W are better for practicing reloads. Otherwise the Umarex line is the clear winner for me. The Colt M4 Ops provides an overall higher quality, higher percentage metal build, more realistic weight and feel, and tunable carrier for various loads. It runs cleaner, is easier to clean, has higher quality magazines, and the accuracy is far superior accuracy with the German made Carl Walther barrel liner.

Running the majority of AR training, dominant to weak shoulder transitioning drills, and speed shooting drills, I reach for the Colt. It shoots smoother and more accurately, and most importantly, it feels like the weight of a full caliber 5.56 version. Just like the HK version, the Colt M4 Ops .22LR rimfire AR delivers on look, fit, function, and certainly accuracy and reliability. Just remember to pick up plenty of extra magazines, because you will be shooting this gun a lot.


  • Colt M4 OPS 22 Rimfire AR-15
  • Item No. 2245051
  • Caliber: .22 L.R.
  • Capacity: 30-round Detachable Magazine
  • Mode of Fire: Semi-Auto
  • Barrel Length: 16.2 in (412 mm)
  • Barrel Twist: 1 in 13-3/4 in
  • Rifling Grooves: 6
  • Rifling Length: 13.78 in (350 mm)
  • Front Sight: Adjustable – Elevation
  • Rear Sight: Detachable, Adjustable – Windage & Elevation
  • Overall Length: 31.1–34.4 in (790-875 mm)
  • Overall Height: 9.1 in (230 mm) w/Mag
  • Overall Width: 2.6 in (65 mm)
  • Stock Style: Adjustable Telestock
  • Trigger Type: Single-stage
  • Trigger Pull: 6.6-9.9 lbs
  • Safety Type: Manual
  • Operation: Blowback
  • Muzzle Thread: M8x.75
  • Length of Pull: 13-7/8 IN
  • Sight Radius: 14.8 in (375 mm)
  • Rear Sight: Aperture .06 / .2 in
  • Front Sight: Width .08 in (2 mm)
  • Weight w/out Mag: 5.9 lbs (2830 g)
  • Weight of empty: 4.2 oz (120 g) Mag-30
  • Features Full metal body
  • Rail interface system
  • Flat top receiver
  • Street Price: $499
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By Major Pandemic – Is the editor at large of which features hundreds of deep product reviews. No my name is not Pandemic, nor am I a Major, I am but a mortal being, using my freedom, intelligence, and available resources provided in this great free nation to survive another day. Hopefully I can help you get smarter and live longer and enjoy the outdoor more comfortably and more safely.-

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