Suggestions for mis-feeding CMMG MKG 45acp?

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  • Karl-just-Karl

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    I'll try to keep this tidy, but it seems like a messy problem.

    Glock 21 magazines, usually loaded to just 10 rounds for square range paper punching.
    Inconsistent feeding, but always on the 3rd to the last round when it occurs...always.
    I haven't been able to get the misfeed to occur when I only load 5 rounds in the mag. :dunno:

    The misfeed usually involves a bolt over-ride of the round and a nose up condition.

    I've tried American Eagle, S&B, Independence, UMC, my own reloads. All of it 230gn ball; some plated, some FMJ.
    The malfunction frequency changes with the ammo, but seems to be more dependent upon which mag I am using.

    It is also amazingly, consistently inconsistent. The only consistency when it occurs is that is always 3rd from the last round, always 3rd from the last...unless I only loaded 5.

    I've considered calling CMMG, they have been helpful on other problems I had with one of their other firearms. I'm just afraid of sending it back and and getting the response that they couldn't get it to malfunction.

    So, mag problem? Finicky ammo-gun? Does anybody have any opinions on the Glock extra-power springs?

    Just being cheap, trollin' for the easy solution...thanks.
     

    Tactically Fat

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    Have you marked the mags that this happens with? Or does it happen to all the mags?

    If you've marked the problem mags, I'd start by replacing a follower or two in those mags. Should be a cheap and easy way to determine? Springs, too.
     

    Karl-just-Karl

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    Yep, marked all the mags. It happens with all the mags, some are better than others. Ammo vs mags is something I just started playing with.

    I haven't considered the followers. Is there something aftermarket?
    I was looking at the springs on Midway, they are only 7 bucks, I might throw a couple in the cart next time I order.
     

    Bigtanker

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    Try resting the gun on the mag when you fire it if you can. From your description, a mag seating issue seems most likely.
     

    Karl-just-Karl

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    Thanks, I'll give that a try.

    I looked up the specs for the feed-lip gap. Mine look to be a little on the tight side. I'm not certain if that is intentional to account for wear or not.
    I figured I would find the worst performing mag and then start experimenting on it.
     

    Karl-just-Karl

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    Alrighty! I made it back to the range.

    I loaded up a magazine, first time, three rounds to go, misfeed. I done it again, misfeed again!
    I tried the mono-pod on the magazine. No problems. Did it again. No problems.
    Went back to standing and the magazine fell out of the gun. That took me a little by surprise. That never happened before. So I reloaded the mag, made certain it was seated, three to the end the magazine fell on the ground and I was certain I was nowhere near the release.

    Upon inspection of the magazine, I saw that there was now a burr, or lip, raised up on the mag catch/notch. The plastic is deformed and cold-flowed. I tried to get a picture of it, but it is small and black on black is hard to get a photo of it.

    I guess CMMG is going to be contacted today.
     

    Karl-just-Karl

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    After a week of negotiations and sending photos to CMMG, it looks like a trip to Missouri is required for inspection and evaluation.

    I'll probably end the updates here. Customer service response has been positive.

    It is a pet peeve of mine that troubleshooting threads rarely have any closure.
     

    Karl-just-Karl

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    Just another update for the story...

    CMMG has opened the mag well, replaced the mag catch and added a mag catch shim.

    For whatever its worth, maybe someone will find the information useful.
     

    WebSnyper

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    Just another update for the story...

    CMMG has opened the mag well, replaced the mag catch and added a mag catch shim.

    For whatever its worth, maybe someone will find the information useful.

    Is it still on its way back or did you already get it? Interested to hear if this fixes it.
     

    Trapper Jim

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    Alrighty! I made it back to the range.



    Upon inspection of the magazine, I saw that there was now a burr, or lip, raised up on the mag catch/notch. The plastic is deformed and cold-flowed. I tried to get a picture of it, but it is small and black on black is hard to get a photo of it.

    I guess CMMG is going to be contacted today.


    Wait. Plastic?

    hope the gun is for playtime only:):
     

    Karl-just-Karl

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    WebSnyper: I'm supposed to get it back today. I'm hoping to get a couple of range trips in this week to give it a through testing. Interesting thing, CMMG sent me a link to a video of them test firing it post-repair. Someone from the company held up an RMA slip to the camera like it was the newspaper in some sort hostage situation showing proof of life. It was pretty brief and showed them doing a mag dump with only one mag. Considering the malfunction was intermittent I hope they test fired more than one mag to prove their repair. If not, I certainly will.

    So far CMMG seems to be standing behind their Lifetime Gaurantee. This was also tested a while ago with a MK47. The CMMG CS has been pretty good. I just regret having to use it.

    Trapper Jim: Plastic=Glock mags. The mag catch is metal. Range toy? Perhaps. Go ahead and step into that mess if you want to.:):

    I was willing (once again) to be a Beta-tester and picked up a MKG, which is a 45ACP AR based design which utilizes Glock mags, about a year ago. After the first few hundred rounds the malfunctions were reduced to only one kind as described at the beginning of this thread. I considered a lot of them to be "break-in" pains. After a while I grew more displeased with the frequency of the mis-feeds as they seemed to be increasing after initially falling off.

    I was told by the service tech that based on my serial number it was an earlier version and they had made some changes. The changes weren't described. I'm looking forward to getting it back and seeing how it runs!
     

    Trapper Jim

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    Trapper Jim: Plastic=Glock mags. The mag catch is metal. Range toy? Perhaps. Go ahead and step into that mess

    No worries as I have many range toys that are fun to shoot as well but I try to help many Ingoers that would carry substandard toys on the street. It boils down to what your life is worth when it comes to the number one rule of gun fighting.
     

    Karl-just-Karl

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    Range toy, it is fun when I don't have to clear a jam third round to the end.
    Zombie/apocalypse gun, not if I have to worry about a jam third round to the end.

    If it runs 100% I might consider it for HD.

    The mess I was referring to was plastic=Glock mags might relegate it to being a range toy=Glocks are only range toys. :runaway:

    UPS delivered it last night about 1900. I'm hoping to take it out tomorrow or Friday and then again on Saturday. I'd like to get 250 rounds through it and see how it does.
     

    Karl-just-Karl

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    So I managed to put 300 rounds through it between Friday and Saturday. I cleaned it fresh for the Saturday session.

    The problems persist. Overall performance was better. The misfeeds were still worse with some magazines than others. My reloads were worst performing (5.3gn 231 for a 230gn RN) with a couple of magazines in particular. I still saw the malfunction with some factory ammo. Of course there were lots of rounds fired without any misfeeds.

    My next experiment is to cut some 0.25" material that fits in the bottom of the magazine. This should increase the spring tension. I theorize that this should put whatever evil happens in the magazine spring tension decompression curve half a step off of what it usually is. This might push the malfunction to the fourth or second to the last round (as opposed to the third) or eliminate the issue if there is some strange combination of forces and timing that is causing the issue.

    Of course this makes it a 12 round magazine instead of 13. I'd rather have a 100% feeding firearm than the extra round.

    I also received lots of suggestions from the regulars at the range. Send it back to CMMG, lighter buffer, lighter buffer spring, stronger magazine spring, put more oil on it, etc... One step at a time.
     

    Karl-just-Karl

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    I tried to add the 0.25" spacers to the bottom of the worst performing magazines. One it helped perform better, the second it causes it to choke almost every time.

    The mystery continues.

    I'm probably going to contact CMMG again to find out if there is anything else they can/will do before I do any serious tinkering.
     

    Karl-just-Karl

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    An update for anyone who follows such things.

    After contacting CMMG again they suggested I try using Winchester White Box. Strangely enough, it seemed to run a lot better. There were still a couple of misfeeds, but there was a noticeable increase in reliability.

    Does anyone have any suggestions why WWB would make a difference? Of all the other factory ammos (AE,S&B, Independence,UMC) I tried I just have a hard time swallowing the pill that the preferred ammo for this firearm is WWB.

    I'm still tempted to buy another buffer spring and take off a coil or two or try a different buffer.
     

    churchmouse

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    An update for anyone who follows such things.

    After contacting CMMG again they suggested I try using Winchester White Box. Strangely enough, it seemed to run a lot better. There were still a couple of misfeeds, but there was a noticeable increase in reliability.

    Does anyone have any suggestions why WWB would make a difference? Of all the other factory ammos (AE,S&B, Independence,UMC) I tried I just have a hard time swallowing the pill that the preferred ammo for this firearm is WWB.

    I'm still tempted to buy another buffer spring and take off a coil or two or try a different buffer.

    WWB as the go to is confusing.

    You mentioned forces at work being the cause. That far up on the spring does seem very unusual.
    We have used a lot of CMMG parts/pieces etc over time with good results.
    It seems you enjoy tinkering. Just be careful doing to much and then having to send it back and CMMG saying no joy.
     

    Karl-just-Karl

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    Chapter 17: The saga continues

    CMMG had me return my mags to them with the promise they would send me new mags. They tested my mags and said they had no problem with them so they sent me no mags. Now they want me to return the firearm to them for a second trip back to its birthplace.

    The plan from CS was to have me send in my old mags so they could send me new mags and have me return to the range. If the firearm continued to malfunction they wanted me to take a video of me shooting to ensure I was not inducing the malfunction with my technique.

    I have yet to tinker with anything.

    I now feel compelled to continue this thread for the sake of posterity. May someone else find comfort or insight in this adventure.
     
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