C Products 9mm AR15 Mags won't feed properly?????

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Hi Guys

I got 5 of the C Products LAR-15 Ten Round AR 'Pistol' Magazines from Questar. I tried them in my Rock river arms 9mm ar and they don't work. They usually jam every 2 or 3 rounds. 90% of the time this is because it fails to eject the spent casing and then the bolt closes on the spent casing. My ar works fine with a pro mag nylon magazine or modified uzi mags.
I had another guy at the range try the c-products magazine in his ar, and they did not function in it either.
Has anyone had a similar problem? Any suggestions on what to do to fix it?
This is my first ar and my first feed problem, so I don't even know where to start.

Thanks!

 

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If this AR of yours is the type with an aftermarket mag-block you may have to tweak the ejector a bit... Bending it in towards center..
The mag block itself may need to be moved a few thou up or down..
As far as the mags go... You may want to file the lips down a bit...
I too experienced some difficulty wth the CProducts 9mm mags, but a few passes with a fine file fixed the problem of the bolt rubbing against the feed lips... This may be slowing your bolt in one direction and/or the other causing grief.

Visit AR15.com.. Their pistol cal AR sub forum is full of great info.

I put together a 9mm AR recently and after a few teathing problems similar to yours it now runs problem free..

Another thing to look at is ammo... My buddy also put a 9mm AR together and was having trouble with jams/feeding.. Forensic examination of the ammo he was using reveiled that it was the problem... 'Won't get into it, but stick to FMJ RN boolits.
I also found that the LAR15 9mm pistol mags do hold 10 rounds, but tight. They wouldn't seat easily on a closed bolt.
Disassemble and shave a few though off the follower "legs" so the mags will fit 10.5 rounds...

 

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I looked at the mags closely and it looks as though the bolt wore off the paint a little on the lips. I will try filing one of the mags tomorrow and take it back to the range. I don't want to change anything on the gun just yet since it is working ok with the other mags. Thanks for the advice.

 

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Extractor

When I first got my RRA 10.5 9mm upper I was quite frustrated. I would have at least on FTF with every other mag. Almost all would be a failure to eject, which sounds like your problem. The spent case would extract but not clear the action, and get mangled in along with the next round stripped off the mag.

I tried different ammo, mags and changing the height of the mag block but only using hot 147gn rnds seem to make any difference, but was still problematic.

I did notice two things that concerned me. First, when I would put an empty case in the chamber and cycle it buy hand the case would just fall off the bolt and get stuck in the action. No matter how vigerous I tried to cycle buy hand, the case would fall straight into the action. Second there was alot of brass markings along the inner top of the ejection port from cases.

I decided to get drastic. First I tightened my extractor. I tightened it just enough to get the case to come out and barly clear the ejection port buy hand.

I also put the upper in a mill and opened up my ejection port. This was pretty drastic but I figured people started doing it years ago with the Gov 1911 so what the heck. So with a 1/2" end mill I took off .612" off the top and bottom of my ejection port making .125" wider from the dust cover ball detent forward.(that way I can still close the dust cover).

I never did bend my ejector but I probably could have lowered the angle of ejection and kept the cases from hitting the top of the ejection port if I had bent it up alittle. I never thought of that, but the extra room in the ejection port seems to have solved my second problem.

Now it runs like a top. I have only had two FTF in about 500 rounds, and both failing to chamber the first round when charging buy had. I haven't had any failure to eject since doing my two mods.

If you can get a spare ejector and extractor, then you can go at it. Milling the port is not for everyone, but worked for me.

Gas Can