cmmg upper problems

[psubond]

*edit* i'm home now and have uploaded pics. pretty sure it's the mags now i just need to figure out why they are making the last (sometimes second or third to last) round stand straight up. did it with federal bulk 550 pack hollow points as well as with cci mini mag solid round nose bullets. please help on what to do about the mags really don't want to buy more and would like to be able to use this at an appleseed at the end of the month and would rather not have to send my mags back to cmmg. i trimmed the mags to where they dropped free which means they move around a tiny bit in the mag well but no more than my 5.56 mags do

First day at the range with a new dedicated upper and the last round always gets jammed in the bcg. Its getting pinched at the top. Between the stainless bolt carrier and the collar that has the feed ramp on it but at the top not where the feed ramp is. Its like the rounds are feeding straight up. Does it with both fed 550 and cci mini mags with two diff cmmg10 round mags. Pics to follow I'm still at range trying to figure this out.





this is how the mags had been coming out if i eject them before they jam. now that i'm looking at the pic it looks like the mag is flipping me off. well f**k you too buddy




this is not a typical malfunction only happened twice unlike the other type which got jammed in the bcg (first pic)

[Packy14]

this happened to me when my mags were failing, check the mags

[psubond]

Brand new mags. What should I be looking for to check?

[shadow65]

It's the mags. Do you have access to any BDM mags?

[psubond]

Will have to order some. Almost feels like the spring is too weak in the two mags I have

[shadow65]

Did you adjust the mags for fit in the mag well?
Also, make sure the bolt is closing all the way and not dragging on the bolt catch.
Dave N

[shadow65]

Shouldn't have anything to do with spring pressure. The standard mags don't require the same pressure the BHOA do.
We will get it straightened out. I hate that your first range trip results in problems. Wish I was there to fix it.
Dave N

[psubond]

They fit about the same as my 556 mags. Trimmed them like paper said that came in box

[capitol]

dude dont worry too much because I had several issues with my cmmg upper at first, but after a lil tuning here and there my rifle is running great!

tip: it's the mag

[psubond]

What did you do to fine tune it?

[xbimmers]

I had the same issue when I used Blazer 22LR...it seemed the coating on the lead bullet was gumming up the action. I switched to Federal and have NO problems at all!!!!!!

What ammo are you using?

[shadow65]

I still think it's a bad mag. The same thing will happen if the feed lips are worn.
If you have somewhere close to pick up a BDM mag, grab one. It should work fine and give you something to shoot until CMMG gets the mag taken care of.
Do you have more than one CMMG mag? Are both the same?
I suspect the feed lips are out of spec.
Dave N

[psubond]

yea i have two. both are doing the same ****

[psubond]

will the mags for a S&W or colt work with cmmg upper/stag lower?

[xbimmers]

Shadow, I was having the same issue with all my BDM (Black Dog Machine) mags during the first 100-150 rounds. I have the stainless bolt and collar. I couldn't go through 10 rounds without a failure. It was really pissing me off. I stopped using the Blazer ammo and went with Federal bulk. All is well now.

I still think it's a bad mag. The same thing will happen if the feed lips are worn.
If you have somewhere close to pick up a BDM mag, grab one. It should work fine and give you something to shoot until CMMG gets the mag taken care of.
Do you have more than one CMMG mag? Are both the same?
I suspect the feed lips are out of spec.
Dave N