CMMG .22 Upper Review

[ASH]

If I was running a standard trigger settup, that would be the right track. The WC trigger is a one piece unit with no springs to swap. I have thought about building a dedicated .22 lower for this upper, but the WC trigger works great on the 5.56 and 6.8 upper and those are my main concern.

Do you have another lower w/out a 1 piece trigger? I'm sure you've thought of that already. My lower was the same way, worked great on my 5.56 and 6.8 but not the 9mm.

[HandgunHTR]

68WJ,

Did you see the thread about the guy who shot himself in the leg with his CMMG upper on the Outdoor Trader forum? According to him it wasn't even installed on a lower.

[68WJ]

68WJ,

Did you see the thread about the guy who shot himself in the leg with his CMMG upper on the Outdoor Trader forum? According to him it wasn't even installed on a lower.

Link? Sounds like the opposite problem I was having.

[HandgunHTR]

Here you go.

http://www.theoutdoorstrader.com/thr...KIT-and-no-gun

[DDriller]

I bought a TacSol upper and it has been flawless.

[68WJ]

Ended up selling the upper. The buyer tested it on two lowers before committing to buy. With a RRA 2-stage, it failed just as much as my TTU. With a factory/mil-spec trigger it ran flawlessly.

I still don't think CMMG addressed the issue with the gap between the rear of the bolt and hammer. In my uneducated opinion, allowing the hammer to come all the way forward should provide a reliable amount of energy to the firing pin for most hammers to work. I think the TTU and RRA hammers already hit harder than a Ruger 10/22.

So there it is, my CMMG .22 upper, non-biased, from start to finish. Too bad for me, but hopefully it will help someone out.

[Offroadtek]

Reviving old thread, but wanted to put in my .02.

I had very similar problem with my TacSol upper and Timney 3lb trigger. I had another lower with mil-spec trigger than it worked much better on, but not 100%. With the use of a dremel and file I rounded the lower part of the bolt under the firing pin. This improved reliability alot as well as help out with a little reset issue i have b/c I mostly run 22 subs in it. As for the timney trigger, I ordered a AR10 spring from Timney and now it works great.

[BamaInArk]

Caught this thread now that it was revived. I had debated about getting a CMMG upper but ended up buying a conversion unit initially. I got the top of the line one though.....the Evolution India kit. That is the stainless steel with forward assist, bolt hold back device, charging handle. I built a new upper using a Bushmaster 1:9 barrel. I was not as impressed with the accuracy. So ended up ordering a CMMG .22 barrel. I rebuilt it using the CMMG barrel. MUCH better.

I tried several lowers as well but never saw the misfires as you did OP. It is common knowledge, or reported and written about anyway, that the .22 conversion kits work better with the standard AR rounded hammer. Mine works fine with a notched hammer though....so far. I do have a lower with a Wilson TTU and will give it a try to see if it makes a difference. I have also tried it on a lower with an SSA trigger and no issues there.

There are a couple of users on the Rimfire forum on arfcom that are very knowledgeable of the CMMG stuff. One even tests for CMMG. They are both very helpful to people with issues.

Generally I think the CMMG uppers have high praise however you do read of the few who slip through the cracks and leave some wanting.

Oh and I'm still trying to visualize exactly what was happening with yours. Guess I'm gonna pull mine out and see if I can see what you were talking about.

[68WJ]

I tried several lowers as well but never saw the misfires as you did OP. It is common knowledge, or reported and written about anyway, that the .22 conversion kits work better with the standard AR rounded hammer. Mine works fine with a notched hammer though....so far. I do have a lower with a Wilson TTU and will give it a try to see if it makes a difference. I have also tried it on a lower with an SSA trigger and no issues there.

I don't think it had anything to do with the strength of the hammer and everything to do with a defective assembly or poor design. When the hammer fell, instead of driving the firing pin forward, it made very slight contact with the pin and then came to rest against the bolt stop. The photo that I included previously shows the gap between the hammer's stopping point and the back to the bolt. This is the same result as dry firing your lower without the upper in place. I realized that this was happening when I attempted to shoot once and noticed the bolt stop jump. Essentially, the firing pin was only receiving a fraction of the available force before the bolt catch interfered.

So, was it maybe a defective lower or bolt catch? Based on two other centerfire uppers not having this interference issue, I think the lower parts are good.

CMMG's response was that they test fired it and it worked. They also added that the gap was normal, and in a typical centerfire setup the hammer is stopped by the back of the carrier and doesn't rest on the firing pin either. I don't agree with that on fully shrouded carriers, and it is obviously erroneous on open carriers.

[BamaInArk]

Okay I'm playing with a few of my lowers here and trying my .22 upper. I realize your upper is gone now so this really doesn't matter. But some of what you were seeing got me curious.

First of all I was wondering how you even got the pic of the hammer and firing pin. I think you mentioned being able to look through the ejection port on your upper? I have noticed on most of my lowers, with the upper removed, the hammer strikes(touches) the bolt catch slightly before the hammer hits the receiver frame. My Wilson TTU does that as well. Now my Geiselle triggers do not. They are notched on the lower end of the hammer and do not make contact with the bolt catch at all.

What you are seeing or suspect got me wondering.... just how close does the hammer come to the lower receiver with a normal AR upper installed? I'm not sure how to determine this. With a normal BCG does the hammer strike the firing pin with full force and not allow the hammer to actually hit the receiver? I don't know.

Anyway I put the .22 upper on a Bushmaster lower with the WC TTU trigger and guess what? With it installed I was not able to pull the charging handle. It felt like something was jammed and not allowing the carrier/bolt assy to be pulled back. If I cock the hammer before assembling them together and then drop the hammer, the charging handle again feels stuck. Not sure what it going on there since I haven't tried it with that trigger/hammer combo. Weird!

One other thing I've noticed. I can open the receiver by removing the take down pin and allowing the lowers to pivot. Now on a lower with a rounded hammer I can close the upper easily with the hammer released and against the frame. But with a notched hammer it will not close. I have to cock the hammer back to get the upper to close all the way against the lower. The Geiselle triggers are similar to the rounded hammers. Crap I can't remember what the TTU did. lol Doesn't matter anyway...it doesn't work.

Still testing components. Obviously I won't be trying to shoot that combo. lol I am going to the range tomorrow so will test some other lowers/trigger combos I have available.