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Posted: 10/9/2007 6:45:07 AM EDT
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I've got a 9mm SBR AR, with a 11.5" CMMG upper on a Stag lower with Hahn dedicated mag well block, and it has been giving me fits. I bought two new C Products mags when I first assembled the gun back in July or so. At first these two mags would fall out every third or fourth round, but when I finally managed to empty the mag the bolt would lock back. After a couple of loadings it seems these two mags are okay. I bought three more C Products mags a little later, the ones that were back ordered for so long, and just now got a chance to try them out. The first two of these three new mags fall out on every shot. I can't tell you how annoying that is. I put my hand under the mag to keep it in, but that would cause a malfunction. The fired brass wouldn't eject completely and a the next round would try to chamber anyway. I was so pissed by then I didn't even try the third mag. It was so hot yesterday I didn't feel like troubleshooting the little bastard. Oddly enough, before the mag falls out it picks up and chambers the next round. It must cycle pretty damn fast. Since the first two mags seemed to work out their problems with a couple of firings maybe these would do the same, but the first mags were never this troublesome. I don't feel like going through this process just to break the mags in, in the hopes that the problems go away. Maybe it's not even the magazine's fault. Is the mag catch to blame? It's a Armalite mag catch, I don't know if that matters. I'm to the point where I'm going to yank the 9mm crap out of it and put a LMT 10.5" 5.56mm upper on it and be done with it. It was my plan to get a suppressor for the 9mm setup, but it won't be much fun if I have to keep sticking the mag back in. 
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I had this issue a couple of years ago with Colt mags. The remedy that worked for me: 1) Added tension to the mag catch by giving it a couple of more turns. 2) I moved the mag block around little to fine the sweet spot for proper mag engagement. (This may be difficult due to you using the Hahn dedicated mag block, I use the bottom loader. 3) I also swapped out the DPMS mag catch to a CMT part, the CMT catch seemed to fit better in the mag catch slot in the mag. Also, when you insert a loaded mag, give it a tug to make sure it is properly seated. |
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I failed to mention that during my problems with the first two mags, I tightened the mag catch. I also give the mags a yank after inserting them to ensure they're seated. The weather is supposed to cool off this weekend, and maybe by early next week I can get out and try again. This time I'll take that gun and no other so I can concentrate solely on it. It was just too hot yesterday for me to try anything else to keep it going. Maybe cooler weather will help keep my head cool. 
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Try twiswting the mags to see if they fell out. I'd pull and pull on mine to see if they would jerk out of the magwell, and they didnt, but they fell out when firing. So, yes, I know how annoying it is. Lets not forget that when a loaded colt mag hits the floor, it unloads itself. So I think I had it a little worse. Anyway, I wouldnt say its a common problems, but it happens a little too often to be uncommon. Basicly, the mag catch isnt deep enough in the magazine. Some members have filed the slot into the back of the mag deeper, others have managed to bend the mag catch where it sits deeper in the mag, and there are a few of us who swapped it with another part and been fine. I'm sure I'm forgetting something. Anyway, when I had the same problem, I replaced my mag catch with a DPMS part. I had to, because I broke my RRA catch when I tried to bend it. If you've got more than one AR, try a mag catch out of one of them. |
Take the mag catch out and put it on your work bench with the threaded part pointing up . Where the threaded part is connected to the flat area of the catch, take down the flat area around the stud with a dremel about 1/16", and this WILL fix your problem. When the mag catch is in the lower, it is in as far as it will go. It does not matter how many more turns you run it, the catch will not sit any deeper until you take some material off the catch . |
I see. I will give that a try as long as I have a spare mag catch, just in case I screw up!
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| I bent the mag catch about 0.020 inward, and also squared up the top edge. Until then, I had the same problem with my RRA as you describe. If pulled straight down, they would always hold. When twisted around a very little bit they would always pop loose; and would always fly out after 1 or 2 rounds fired. Now, I could probably hang a small car and give the mag a twist, with no problem! Be careful not to bent the catch so much that it hits the follower. |
Well, I've done as you said. Now I've got to go out and see how it works. Thanks for your input!
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I haven't tried any other mags. The C-Products mags are the only 9mm mags I have. I would love to get some modified Uzi mags to see how they function, but I am hoping my mag catch modification takes care of the problem. I'm going to try to take it out this week to see how it works. I agree with you 100% about breaking in mags. Ammo is too expensive to be wasting just to try to get a mag to work. |
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