CMMG mag extension failures?

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CMMG mag extension failures?

Post by cornhusker » 12 Mar 2011, 19:22

I am new here so apologize if this is a repost but have only just now obtained a brand new USG FsN, and also picked up 2 CMMG mag extensions but have not yet installed them because I saw a video review about them not feeding properly. The individual said that he had trouble with rounds not feeding properly withthe supplied CMMG replacement spring installed but that he had no problems with misfeeds using the stock FN magazine spring with the CMMG extension. I am leary about using the stock spring with the extension since that is not how FN designed it to be used but also dont want to have to worry about critical failure to feed when it counts and am just wondering what experiences, good or bad, others have had with the CMMG 10 round mag extensions.

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Re: CMMG mag extension failures?

Post by PainKillaX » 12 Mar 2011, 19:43

There are quite a few threads regarding problems with the CMMG/ProMag extensions. It's generally advised to clean the heck out of them and check the mag+extension body for bits of extra plastic where the follower can catch. Elite Ammunition, a forum sponsor at the top, sells more powerful springs for a great price. There's more info but it's not coming to me right now, give the search bar at the top a go. It may not bring up exactly what you want since it works off keywords but you'll find something. Someone more knowledgeable than myself should be along soon.

If your concern is failure at a critical moment, just keep a self defense 20 rounder loaded and carry that, and use the 30 rounders at the range for giggles. Cause honestly, if you need more than 20 right that second, you're already in trouble :)

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Re: CMMG mag extension failures?

Post by Esteves » 12 Mar 2011, 19:45

Some of the extensions seem to fit and function fine. Others seem to require a bit of work with a file & sandpaper in order to feed reliably.

They're fun at the range. I don't (personally) carry them for defense. YMMV.
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Re: CMMG mag extension failures?

Post by smpsmp » 12 Mar 2011, 19:49

I would recommend, as PainKiller said, go with the elite ammunition springs (if they aren't functioning after you test them), but don't bother with the extensions for carry, stick with the 20 round for SD.

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Re: CMMG mag extension failures?

Post by fzr confused » 12 Mar 2011, 20:42

i have 4 CMMG extensions and they all function fine. but like everyone else, i only carry my FsN with the 20rd mags in them. the added length makes it harder to conceal in FL weather clothes.

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Re: CMMG mag extension failures?

Post by DmL5 » 13 Mar 2011, 00:00

I haven't had any problems with my magazine (CMMG).

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Re: CMMG mag extension failures?

Post by Nickf150fx4 » 13 Mar 2011, 15:01

No problems so far with my CMMG extension and i'm using my factory spring instead of the CMMG spring. I only have about 200 rounds through it now though. I would also recommend getting the Elite Ammo springs to put in all of your magazines. I plan on doing this pretty soon, but for now i'm just using the factory spring. Theres a bunch of other great posts on here that talk about the different extension and what to expect here's a few to get you started.. :thumb:

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viewtopic.php?f=15&t=9679" onclick=";return false;

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Re: CMMG mag extension failures?

Post by DarkWater » 13 Mar 2011, 21:22

mine took some work...sanding/scraping mold marks off to get the follower plate to move past the interface normal mag to extension. had to redo it a few times (didn't want to take too much off first time around...). now they work very well.
don't let the spring bite you when you pop the mags open....

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Re: CMMG mag extension failures?

Post by DBrigade81 » 16 Mar 2011, 15:10

I just received my extension today and it did have a few burs around the edges. I filed them off and it seems to be functioning properly. I will see for sure this weekend when I load 30 rounds and see how it feeds.

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Re: CMMG mag extension failures?

Post by Mister Freeze » 16 Mar 2011, 18:07

When I carry my FsN, it's with the 20 rounder. 30's are for backup. I've used 30's in competition and at the range; no failures.

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Re: CMMG mag extension failures?

Post by section88co » 19 Mar 2011, 18:39

I tried a couple CMMG's and have had failures to feed on the first few rounds every time like the CMMG springs are too stiff, would trying the factory springs work better? Do I need to try and stretch the factory spring to make it a little longer or will it work fine as is? Thanks!

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Re: CMMG mag extension failures?

Post by blueorison » 19 Mar 2011, 21:02

Section, did you even bother reading the thread? :ponder:
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Re: CMMG mag extension failures?

Post by smportis » 22 Mar 2011, 11:16

blueorison wrote:Section, did you even bother reading the thread? :ponder:
Nah, why do that? They are just repeating what Section already said. :D

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Re: CMMG mag extension failures?

Post by murphytech » 26 Apr 2011, 07:44

heres a video of my cmmg failure with both factory sprint tested and what came with the cmmg. After a couple of uses the cmmg killed my magazine." onclick=";return false;

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