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Posted: 6/17/2007 6:28:39 AM EDT
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After this AR gets hot (5-10 rounds) I start experiencing stuck rounds in the chamber. First couple the bolt will pull back and the round can be tapped out with a cleaning rod fairly easily, but if you do that a few times and it really gets warm then eventually a round will lodge in the chamber with the bolt also stuck forward. This requires MUCH more force to 'tap' out. This happend with Wolf and then the mil spec Winchester Q3131A. The missing primer is a result of tapping the round out I think, as all the primers were missing in the ones that I had to forceably extract. What is causing this, I am fearing a bad chamber, but I really dont know. Here is a pic, is the ring that is about 5mm forward of the rear of shell normal? 
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It's a DPMS lower with this unknown upper The barrel is marked 5.56 NATO. It was spic and span, looked like it was un-shot. |
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Hmm....Best thing I can come up with is for you to take the upper to a good gunsmith who can check out the chamber dimensions and tell if it's proper or not. If that is a Rock barrel , someone may have ordered the blank from Mike Rock and then screwed up while cutting the chamber. Other than that , if you keep it clean and you're using good ammo(and clean it when switching from Wolf to brass case stuff) , I don't know what to tell you. I'm sure someone with more technical knowledge than me will be along shortly though. 
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Start here, www.ar15.com/forums/topic.html?b=3&f=66&t=332322 And, any ammo chased after Wolf ammo fouling is going to be problems. It's not that wolf is evil ammo, its just leaves behind a polyurethane fouling, and takes a chamber brushes to remove it. |
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Looks like you have a big overpressure problem. I have never seen any brass flow into the extractor notch and ejector like that personally. Exept those thad KB'd due to overpressure (squibs or pistol powder) I would have the Barrel/chamber Dimensions checked before you shoot that rifle again. Richard |
I agree 100%, this needs to be checked by a 'smith. Ben |
Man oh man, Big Time! Major brass flow into the ejector cutout and the extractor groove. I would suspect a serious headspace problem if this is happening with factory ammo. Also, that primer blew out because of this. Not because you tapped it out with a cleaning rod. |
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This is Rem-UMC 55gr FMJ fired from a RRA AR. The round ejected and the next round was loaded and fired. All I noticed was smoke from the bolt vents. I didn't notice it until I picked up the brass. There was no damage to the rifle and havn't had any problems since. I did check the rest of the Rem-UMC and found there to be little or no bullet crimp with bullets that i could move with my fingers.   |
What you are seeing is excesive pressure signs caused by the bullet being shoved back in to the case upon being fed up the feed ramps. The oridinal problem appears to be a head space issue caused by to deep a chamber or a bad bolt with a face cut to deep. that should be checked out by a gunsmith . Alpha |
| As others have pointed out you are getting SERIOUS overpressure signs. I have never seen brass flow that bad. You are also getting primer flow back into the firing pin hole. The bubble in the middle of the primer indicates it is about to pierce. The black smudges on the end of the case indicate that gas has leaked around the primer. The line around the case indicates the case head is about to seperate. Even one of these signs by itself would indicate extreme overpressure. Whatever the problem is it needs to be fixed before you fire your rifle again. You are very close to blowing up your rifle. |
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BTW the round wont extract because there is so much pressure that when it expands in the chamber the brass doesnt shrink back down after the pressure drops. The following are just guesses. I doubt you have a headspace problem. You may but I dont think that is what is responsible for the overpressure. Too little headspace and the round wouldnt chamber. Too much headspace and you would get the ring around the case but it shouldnt cause the other overpressure signs (primer flow, tough extraction, extractor mark, etc). I would think it is a problem with the throat or chamber dimesions. The problem could be caused by bullet setback but I doubt it. To find out you can chamber a round normally, but dont fire it, extract it and see if the bullet has setback into the case. You need calipers to measure it but you should be able to eyeball it if it is really bad. |
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Great info in this thread. I hadn't heard of looking for the little dimple in the center of the struck primer indicating flow into the firing pin hole. Terrifying! The photos have just about every classic sign of overpressure as you guys explained above. What gets me is that that someone probably sold the OP this upper suspecting that it was screwed up big time. This is not a consumer-grade barreled upper. Who would drop $700 on an upper, fire a few rounds that probably didn't function well at all, and sell it right off with no concern that the issues may have serious safety implications? |
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didnt you already get an answer? www.ar15.com/forums/topic.html?b=3&f=118&t=332474 |
I have a Lothar Walther Match Barrel with a tight .223 chamber on one of my 14,5" ARs (believe it or not its my favourite AR) and on my 20" AR. I shoot every kind of Ammunition including Wolf and austrian Army issue ss109 and have never seen any brass flow like that. Didn't even have any issues up to now. So I don't think it's a .223 or 5.56 chamber issue because both should work fine in any chamber as long as dirt doesn't come into play and the rifle is in good working condition. Richard |
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