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My work-mandated personality profile indicates that I have a severe issue with making promises. According to the head doctors, if I promise to do something, it plagues me until I get it done. Quite the advantage for all those pesky TPS reports, but a real PITA when I promise our readers that I’ll follow up on something and then can’t make it to the range for a few days.  If you’ll remember from my Part 1, I wanted to follow up on three things. Those would be bolt cycling speed, subsonic ammo compatibility, and accuracy with a nice optic aboard. Two of three are complete. We’ll save rapid fire gun porn for a later date if necessary, but I have full confidence that the little Umarex can keep up with my sluggish fingers. However, I’ll substitute the bolt cycling for some choice nuggets on full teardown and cleaning.

Subsonic Ammo

It works!!! In fact, I didn’t have to mess with the bolt return spring at all. I just loaded up some Remington Subsonic ammo and shot to my heart’s content. It made a world of difference in noise and control. Did I mention that it is also quite a bit more accurate than standard ammo? Check out the following examples of noise. Here it is shooting the Winchester Bulk Value Ammo. The box says this is a 36 gr bullet leaving the barrel at 1280 fps.

Here it is shooting the Remington Subsonic ammo. Rated at 38 gr. and leaving the barrel at 1050 fps.

I was using a GoPro camera with the waterproof plate in place. This has proven to be very good at isolating echo and various other background noise. As I’m sure you can tell, I was blessed to have the range mostly to myself.

I shot 100 rounds of the Remington Subsonic and had only one failure. And I’ll chalk that up to a gun that was absolutely filthy. Other than that, no cycling issues whatsoever. I think I may have to call Gemtech or AAC soon to see about suppressor availability. I think a suppressed semi auto .22 might be the world’s greatest rabbit and small varmint gun.


Off a very stable rest using my trusty Leupold Rifleman scope and Burris PEPR mount, I was able to get fairly reliable groups like the one here at 50 yards using the aforementioned Winchester Bulk Value Pack Ammo.

Imagine my surprise when the subsonic rounds consistently put up the following results.

I even took my target out to 100 yards just for fun. Notice the pink X at the top of the page that shows my point of aim. I had the gun sighted at 50 yards and had to hold about 7.5 inches high at 100 yards. Hardly minute of rabbit at that distance, but certainly making better groups than my shotgun.

My guess is that the slower velocity allows to barrel grooves to actually do some work. Looking down the barrel, it looks as if rifling is cut fairly shallow in comparison to other rifling I have seen. I have neither the tools nor the experience to back that claim though.

Cleaning and Maintenance.

YouTube user hughes500pilot has the most comprehensive set of videos out there on cleaning the Umarex M4. If he’s reading this, ping [email protected] so I can thank you properly.

Part 1

Part 2

Part 3

These instructions were EXTREMELY helpful since this info is not covered in the manual. After finally breaking the gun down and giving it a thorough going over, I can confidently say that this gun is not for the neat freaks out there who don’t like a lot of manual labor. If the thought of powder residue sitting in your gun keeps you up at night, you might not be a great Umarex owner.

To clean the M4 thoroughly, you need to completely disassemble it. That process took me about 30 minutes and could easily be down to 10 minutes or less with some practice. However, there are a lot of little pieces to keep track of, and it is generally not a “fun” takedown. If you don’t mind grime in the action, disregard the last paragraph. Here are some pictures that show what 1000+ rounds with very little maintenance looks like.

This is one half of the two-part receiver. Luckily Umarex or Colt or Walther thought to coat the metal parts in something that prevents residue from baking on. Most of this wiped off after a quick scrub with some Hoppes #9.

Unfortunately, the bolt did not receive the same mystery coating. No matter how much I scrubbed and cursed, I could not get the burn marks to go away. Either way, it didn’t seem to make much of a difference in overall function.

After breaking it down, the whole thing seems really flimsy. I realize that .22 LR isn’t exactly a powerhouse round, but a two-piece action? Under that shroud is a barrel that looks thinner than a NY model during fashion week. The whole thing honestly looks like the guts of a quality airsoft gun which makes me wonder how much say Umarex had in the design aspects. I have not had any issues with the gun, but my-oh-my did that tear down make me question the long term viability of this particular rifle.

Bolt Release

I want to revisit the bolt release issue after one of our readers, Slowburn FYI, blew me up in the comments of my original post. Slowburn recommended that I reach inside the magazine well while holding the bolt back to engage the bolt catch. I guess that certainly is one way to do it, but my daddy always taught me not to stick my fingers in dark places where things could snap them off. You won’t find me digging around inside any of my guns while doing a happy hand dance with the other fingers. To prove my point about the bolt release issue, I managed to capture the following footage at the range.

In case it isn’t apparent from the video, I had a round that wouldn’t chamber from the magazine. When I tried to open the bolt and drop the mag, I ran out of hands. At that point, I would have loved to have locked the bolt back, drop the mag, check to make sure everything was clear, and then assess my issue. Instead, I had to switch hands, bull the bolt back, drop the loaded mag, find an empty mag, insert the empty mag, lock the bolt back, and then go about my business. A real Grade A pain if you ask me.

My final assessment is that the Umarex M4 Ops has been a stunningly reliable gun that has given me much joy at a very low cost. It will cycle subsonic ammo (and pretty much anything else you have sitting around). Long run reliability is certainly up in the air, and suspect given the lightweight construction of the action and barrel. Hopefully, future revisions will address that and the 180 degree safety and bolt release.

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  1. Tyler, I contacted Umarex about the safety, and trigger, and their response was no you could not change out the trigger, and that they had no plans on making the safety a 90 degree, or ambidextrous. So even though I really enjoy my Colt/Umarex AR 22 Rimfire, a better trigger and a 90 degreee safety would make it so much better.
    I’m going to have to watch your videos when I get time, for I really want to be able to do a more thorough cleaning. When I purchased the Colt I also looked at the M&P, but it felt like a toy compared to the Colt. And from talking to owners of the M&P, they also had ammo problems, so I’ll stick with the Colt.

    • Hmmm… My M&P 15-22 has been utterly reliable. I’ve got the MOE version. Love it.

      With thousands of rounds through it, the ONLY malfunctions have been the oddball squib round (maybe twice?). I’ve run mostly Federal bulk (500) from Walmart. I have not yet tried sub-sonic ammo, yet.

  2. Subsonic is usually more accurate. It has to do with the bullet crossing the sound barrier and becoming destabilized.

  3. Tyler, just had time to watch the videos, wow, thank you! Didn’t like the superficial way Umarex and many other 22 handgun/rifle manufacturers wanted us to clean our weapons. This was a big help, thanks again!

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