9mm AR magazine issue

[volksjager]

I recently purchased from CMMG this 9mm AR

and have been having a few issues. The main one I set the rifle back to them for repair. The firing pin wouldn't strike the primer or if it did it barely made a dent in the primer and wouldn't fire.
The second issue is the metal mags I bought from brownells. I bought 4 mags and only 2 of them fit without issue. The other 2 would be real tight. Pita to get in and out. I sent them back and their replacements won't even fit in the magwell more than a few cm's. am I buying the wrong mags? Should I just pay extra and order them from CMMG?

 

[paddling_man]

That's, uh, interesting looking.

What magwell block are you using? Specifically what mags? Metalform? Weak fcg spings? I'd remove the slidefire for a nornal stock until reliability was proved good, though i suppose you can just lock the stock.

 

[jd4320t]

My Metalform mags from Brownells fit and run great. I assume you are running the CMMG mag block. You need to adjust the location of the mag block according to the how the mag fits on the mag release. Also, your mag release may be too tight and need backed off a turn or more. As for the BCG I haven't had any issues with my CMMG.

 

[volksjager]

using metalform mags from brownells. 2 work great, the other 4 haven't. just eyeballing them they all look exactly the same.
i don't think it's the mag release as the new mags barely fit into the opening of the magwell.

there is also an issue with either the rail or my sights. they don't want to sit flat on the upper. they fit fine on the quad rail (nice and flat) but they seem crooked on the upper rail.

this is on the quad rail

this view in on the upper rail

on my another AR they lay flat and aren't crooked at all

 

[tradertator]

I had mag fit issues when I was running a mag block. Went to a dedicated 9mm lower with integrated well, problem solved.

 

[volksjager]

I had mag fit issues when I was running a mag block. Went to a dedicated 9mm lower with integrated well, problem solved.

that's what i'm using

 

[jd4320t]

that's what i'm using

I see that now so I was way off.

I'm not familiar with those lowers so I can't say much but hopefully someone will come along.

 

[tradertator]

I was looking at this thread on my phone, and all the pics didn't load so I didn't see your magwell. That really sucks. I haven't encountered a tight fitting mag since purchasing my Rock River lower.

 

[Mr.JAG]

I bought 12 or so metal form mags for my 9mm SBR. Half fit just fine, the other half were too tight to even get them seated. I sold the ill fitting ones to a buddy who's rifle worked just fine with em.

Now, I had a mag-block. I see that your lower is dedicated.

We both have (had) the same issues, but with different setups. The common denominator seems to be the metal form mags. It's possible that their tolerance between runs are too large.

OH, and on the firing pin.

My upper was a CMMG, and the firing pin broke in half during the very first magazine I ran through it. It went through fits of being a jam-o-matic and then running just fine. All the rounds that didn't fire had a very noticeable weak primer hit. I eventually pulled it apart and found my kick-butt 2-piece firing pin. CMMG was kind enough to send me 2 replacement firing pins, springs, and cotter pins at no cost. I have not had a problem sense. The rumor is that they had a bad run of firing pins some time back and I must have got some old stock.

 

[sig1473]

It looks like your Quad rail might be off a tad. Is there any play/wiggle in your quad rail? Is it a free floated rail?

 

[bmbutch]

1st: Thank You for head's up about mag issues.

My CMMG is only a few months old, thus far the 32 rounders have been no issues. I just picked up 2-20 rounders, will be trying them out tomorrow.

My CMMG has been 100% thru ~ 500 rounds or so.

 

[volksjager]

Thank you guys for all the help. I feel better knowing that I'm not crazy and others have had issues with the mags.

It looks like your Quad rail might be off a tad. Is there any play/wiggle in your quad rail? Is it a free floated rail?

It is a free float and no wiggle on the rail. From what I can tell (sorry about the pics as it is hard to see) the rear sight even looks crooked so it makes me think the rail issue is with the upper...but I

 

[DocIndy]

Have you checked the outside dimensions of the mags with a micrometer? Could be an issue with the mag bodies.

 

[volksjager]

no i haven't. i should really get a micrometer...not the first time i've needed one