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Posted: 11/17/2006 8:26:14 PM EDT
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Had my AR-15 out to the range the other day and had my first misfire then my first fail to feed. Thought I'd check with the gurus here and see if there was anything I could do to help avoid them in the future. The gun: Rock River lower, Del-Ton LPK assembled by me; Stag 16" carbine upper; 9mm buffer; Wolff extra power extractor spring; CProducts stainless 30-round mags with Magpul Gen II followers. The ammo: Remington UMC 55 gr. FMJ The misfire was just a click instead of a bang. Waited half a minute, then discarded the round. I would have fired it again, but noticed that the bullet was slightly loose in the case, moving maybe 2mm back and forth. The fail to feed was one I hadn't seen before. I thought it was another misfire, but when I went to check the round, there wasn't one chambered. This happened about halfway down the magazine and didn't happen again. This is a pretty new gun. Less than 200 rounds through it, almost all of them UMC, never the slightest problem before. I clean and lube after every trip to the range. Same magazines this time, but the extractor spring and 9mm buffer were both new. Which bugs me, because both were added for reliability. The dud doesn't bother me too much. What was a little weird is that I also had a dud out of my 870 the same day. That was with Remington Express 00, but I've had maybe 500 rounds of Remington Gun Club through that gun with never a hiccup. What does bother me is the failure to chamber the round. I'm new to the AR, but haven't seen this one before. Is this somewhat common? Is there anything I can do to help improve my reliability? Have I been led astray by the 9mm buffer? After the dud, I noticed more of the UMC rounds had the loose bullet problem, mostly if they'd been chambered, then ejected. Everything shot fine and as accurate as I am, though. It seems possible that the bullet moving could cause problems, but not a failure to strip the round from the mag like I had. Okay, I think that's all I have to give. I look forward to your help and responses. |
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The loose bullets are low feeds out of the mag, the tip of the bullet striking the barrel/receiver below the feed ramps, and this causes the jam, bullet set back. Could be just mags needing to be broken-in or cleaned, to the rifle fouling out, and this later causing a less than stellar stoke. A clean/full force B/C-buffer stoke causes a jolt to the rifle (buffer off the back of the receiver extension), and this jolt assisted the a new/rough/questionable mag in getting the top round top round in the mag into the correct position. Also to point out, pull the 9MM buffer ad install a standard carbine buffer since the combo of a new rifle, and the ammo at hand does not warrant such use. |
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Dano, thank you very much for the thorough response. That's a good idea on the loose bullets. And it's upsetting. Is there anything I can do to correct that? I hope it's not the mags; I sort of have to use them. I haven't had a chance to clean it yet, so I just took the upper off and checked out the inside. There aren't any noticeable marks below the feed ramps from the bullets. I thought maybe the copper jacket would leave a mark if it was slamming into the receiver there. I don't think the trouble was caused by the rifle or mags being dirty. Both were thoroughly cleaned after the last use. The misfire happened like ten rounds in and the fail to strip happened less than 100 rounds in. I was talking on here about the 9mm buffer before I got it and was told that, even if it was a bit heavier than it needed to be, it wouldn't hurt anything. What are the negatives of using it? Back to the fail to strip. I'll do some testing and report back. I'm thinking if I mark the receiver below the feedramps with a pencil, I should see marks if it's hitting low, like you suggested. I'll also be more thorough about tracking mags and see if it's just one doing it or all of them. One last thing. Is there a downside to installing a heavier hammer spring to help with hard primers? It won't bother me if it makes the trigger slightly heavier. Thank you again. |
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Okay, thoroughly cleaned and lubed today. I couldn't get to the range, but did an experiment at home. First, did the 45-degree test with the bolt sliding into position. That worked fine and it locked into place. I examined the feed ramps as best I could. I didn't see any marks below or any rough spots. It's possible that the receiver is overlapping the feed ramps by a fraction of a millimeter, but I may be just making that up. When looking for debris in a tire at the bike shop, we sometimes dragged a cotton ball across to snag the invisible bit of glass or whatever. I went over the feed ramps with a cotton swab, but no snags. I marked my three mags and loaded five rounds into each. I loaded the mags and manually cycled all five rounds out and kept track of which went with which. For each mag, a couple of rounds ended up with a bullet that would move. No correlation between where in the mag the round was. Examining each round, there was a very small nick in the bullet at what looks like is the same place on each, a couple of millimeters from the nose. When I say they move, I don't mean much. Some I can't even see it moving, but I can just barely feel it. The worst have the notches around the base (can't quite remember the name) moved from just visible to hidden below the case rim. I'm not sure if I'm being paranoid or what. I shot a little over a hundred rounds the other day and had the one misfire and the one failure to strip. Heck, I don't really think this, but now I'm even wondering if maybe it was me. If I'd cleared the rifle, and dropped the bolt before inserting the mag, that would have caused the empty chamber I found after the click. I can't really imagine that I did that, but I guess it's not impossible. This is my only rifle, so I'm very anxious for it to work flawlessly. I think I owe myself another range trip in the next few days. A couple hundred more rounds downrange without problems will probably do more to ease my mind than anything else. Anyway, thoughts or opinions are always appreciated. I can post pictures of anything I'm not explaining clearly. My first worry is the failure to strip and my new worry is the bullets moving in the case. Thanks. |
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The rifle and mag break-in should solve all the problems, but until you hit the 1K fired mark, clean and lube the rifle more than you normally would. Out the gate, around the 200 mark is the norm before some of the rifles just fouls out on the civilian builds (powderized anodizing/parkerizing, and gunpowder fouling)*. Once the rifle starts to mate together, you should be able to take it a bit longer before cleanings, but on the norm, it's nor a bad idea to slightly pull back on the charging handle and apply a few drops of CLP into the carrier exhaust ports. CLP applied to the gas chamber will migrate throughout the action in a few shots, and will keep you in the hunt. * With the heaver than normal buffer, this accelerates the choking process since not only do you have additional fouling friction, you have the additional mass slowing the stroke down as well. |
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