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Posted: 4/12/2008 10:40:57 PM
Bump to keep some good info active!
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Dano523
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Posted: 4/13/2008 12:10:40 AM
Not needed to bump the thread to keep it active.
It has been tacked, and will stay at the top of the forum like the other tacked threads.  |
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Posted: 6/5/2008 7:30:33 PM
you said armalite was gonna take the rifle back and go over it??.
it was never a ammo problem,and doubt was chamber issue. if a ar is working correctly you can take a handfull of differant ammo,mix them up,,theyll all roll thru. somtimes it a simple deal,,try a differant bolt,and all the stupid springs and doughnuts wont cure a extractor claw edge that not sharp and undercut correctly. you can run a stock spring if the claw is correct.,,springs are a great help but are a bandaid to the real problem a ar is very simple but you need the correct tuneup/balance. every one i have will eat all ammo,and they never stop.,,ill bet your hs is ok,,try a simple bolt,,a colt one i wouldnt do a thing if there gonna go over the rifle,,,,its almost always a simple problem,,and most times ar people will buy there way thru issues,,dont do that.... good luck brad |
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wrecktech
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Posted: 7/28/2008 4:48:41 PM
Yes, they did take two back and when I got them back, the free-bore had been extended and velocity was reduced to normal levels. Since there was such a problem we replaced all the uppers with units from another vendor. Now the original units are sitting gathering dust.
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hotbiggun42
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Posted: 7/30/2008 9:06:55 PM
where did the pics go i am having simuliar issues and yould like to see the markings on the casings
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wrecktech
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Posted: 8/10/2008 9:19:07 AM
[Last Edit: 9/30/2008 9:57:05 PM by wrecktech]
Luckily I was able to restore the pictures and put them on the new photo server here on ARFcom. The images have been restored to their original messages and should all be present. I'm sorry for any inconvenience the lack of pictures may have caused.
I am also happy to report that there have been some new developments in this saga. I hope to present new information in the near future with additional chamber cast photos, bullet / cartridge comparisons and chamber information. Without being too theatrical, please stay tuned... |
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Posted: 11/23/2008 10:09:56 AM
Wow, glad I found this thread. We have dozens of 10" M4s having this problem w/ XM193. It is getting ridiculous having to take apart a gun every range day b/c a primer is stuck somewhere. The uppers have about 4,000-5,000 rounds through them in 2 years. When I first got mine my zero groups at 50yds had the holes touching. Now, I could not get my to hold less than 4" at 25 yards of a benchrest...I had other shooters attempt to zero it w/ similar results...is this related to head space??? |
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nf9648
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Posted: 11/24/2008 3:14:44 AM
My rifle recently started having the same issues, I am loading 77 gr SMKs in LC brass with 23.0 gr RE15 at 2.26" OAL and blowing primers, today I had to beat my bolt with a punch and hammer to separate my upper from lower then beat the bolt assy out because a primer got caught in the bolt cam and froze the assy in the receiver. Granted this upper has in excess of 8k rounds (most winchester 5.56 white box ammo and federal .223) but never an issue til the last 500 rounds or so, only with reloads that are over a grain lighter than max in all published reload data. Today was the final straw, I will be replacing this CMMG upper with a LMT MRP and rebuilding this upper with a noveske barrel to go on a different lower I have laying around that doesnt see the range much.
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Dano523
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Posted: 11/24/2008 3:14:11 PM
Originally Posted By nf9648:
My rifle recently started having the same issues, I am loading 77 gr SMKs in LC brass with 23.0 gr RE15 at 2.26" OAL and blowing primers, today I had to beat my bolt with a punch and hammer to separate my upper from lower then beat the bolt assy out because a primer got caught in the bolt cam and froze the assy in the receiver. Granted this upper has in excess of 8k rounds (most winchester 5.56 white box ammo and federal .223) but never an issue til the last 500 rounds or so, only with reloads that are over a grain lighter than max in all published reload data. Today was the final straw, I will be replacing this CMMG upper with a LMT MRP and rebuilding this upper with a noveske barrel to go on a different lower I have laying around that doesnt see the range much. Using slower powder to get increased speeds with heaver bullets is not out of the norm (Fed did it with their match ammo), but the problem is the slower powder causes higher gas port pressures, and does end up with blown primers in the auto's (same happened with the Fed match ammo). If you are going to go this way of slower powders with heaver bullets, then you will need to tune the gas system for such. In the case of your current rig, going with either more B/C-Buffer mass or just an adjustable gas tube would help to resolve the problems by slowing down the unlock and allowing more barrel resudial pressures to lessen to allow the spent case to the pulled from the chamber. That is as long as you are not working beyond standard working pressures as a whole,and just welding the spent case to the chamber. In your case, the question comes down to if the bolt did first start to unlock, and pull the case a fraction of the way out, then just slammed the larger than normal case back into the chamber, or was the case just welded in place from the start that caused the stuck case. Again, if the first, then slowing the unlock down will help. If the latter, then you need to back your loads off. Lastly, this ain't no bolt action rifle, so you have to take the loading manuals with a grain of salt. Back your starting loads off as stated in any manual, then work them up for signs of over pressure and function is such a rig. Starting from/near any max load will get you in trouble, even in a bolt action rifle since your cases could be different volumes that what they where using, or better yet, your chamber tighter than the test barrel they had. |
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Posted: 12/11/2008 12:19:39 AM
didnt the first note say it had never had this problem,but just started?
Keep the reamer out of the chamber,try a new bolt ,or at least mike the thicknes of the locking lugs a properly set up ar will run all ammo,i mix and match all the time when plinking,i never ever have faults/stops.... good luck brad |
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nf9648
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Posted: 12/26/2008 8:25:07 PM
Originally Posted By Dano523:
Originally Posted By nf9648:
My rifle recently started having the same issues, I am loading 77 gr SMKs in LC brass with 23.0 gr RE15 at 2.26" OAL and blowing primers, today I had to beat my bolt with a punch and hammer to separate my upper from lower then beat the bolt assy out because a primer got caught in the bolt cam and froze the assy in the receiver. Granted this upper has in excess of 8k rounds (most winchester 5.56 white box ammo and federal .223) but never an issue til the last 500 rounds or so, only with reloads that are over a grain lighter than max in all published reload data. Today was the final straw, I will be replacing this CMMG upper with a LMT MRP and rebuilding this upper with a noveske barrel to go on a different lower I have laying around that doesnt see the range much. Using slower powder to get increased speeds with heaver bullets is not out of the norm (Fed did it with their match ammo), but the problem is the slower powder causes higher gas port pressures, and does end up with blown primers in the auto's (same happened with the Fed match ammo). If you are going to go this way of slower powders with heaver bullets, then you will need to tune the gas system for such. In the case of your current rig, going with either more B/C-Buffer mass or just an adjustable gas tube would help to resolve the problems by slowing down the unlock and allowing more barrel resudial pressures to lessen to allow the spent case to the pulled from the chamber. That is as long as you are not working beyond standard working pressures as a whole,and just welding the spent case to the chamber. In your case, the question comes down to if the bolt did first start to unlock, and pull the case a fraction of the way out, then just slammed the larger than normal case back into the chamber, or was the case just welded in place from the start that caused the stuck case. Again, if the first, then slowing the unlock down will help. If the latter, then you need to back your loads off. Lastly, this ain't no bolt action rifle, so you have to take the loading manuals with a grain of salt. Back your starting loads off as stated in any manual, then work them up for signs of over pressure and function is such a rig. Starting from/near any max load will get you in trouble, even in a bolt action rifle since your cases could be different volumes that what they where using, or better yet, your chamber tighter than the test barrel they had. My brass ejects from the rifle fine, unfortunately so do the primers from the brass. |
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Posted: 1/2/2009 7:54:17 PM
Not to highjack this topic... but I have a question about reloading the brass.
The first 70-80 rounds out of my new AR exhibited the same overpressure marks on the case heads, just like the ones shown in the photos at the top of page 2 of this thread. I'll need to test the gun a bit more, try some different brands of ammo, see if the problem continues, etc. Absolutely no problems with ejection or feeding, though. However, all my new empty Lake City brass has these same marks on the case head. Is it safe to reload these, or should I kiss them goodbye? |
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Posted: 1/4/2009 3:38:21 PM
I bought a headspace field guage to see if that was the issue and it did not close on it.
My rifle has also lost accuracy badly. Going from 1" groups at 50yds to all over the paper consistetly. I cleaned it. I had several top shooters shoot it. It is jacked. Still blowing primers too. |
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Posted: 1/4/2009 6:34:01 PM
Here is a test I did today:
XM193 on left. Federal AE .223 on right. Using my 10" CMMG 5.56 upper at 25 yards. Didnt take forever, maybe 2-seconds per shot using my VFG on my range bag as a rest. The XM193 is what is also blowing primers. There is something about this gun/ammo combo that is not working... |
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wrecktech
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Posted: 1/10/2009 12:04:52 AM
[Last Edit: 1/10/2009 12:13:33 AM by wrecktech]
Originally Posted By MP906:
Wow, glad I found this thread. We have dozens of 10" M4s having this problem w/ XM193. It is getting ridiculous having to take apart a gun every range day b/c a primer is stuck somewhere. The uppers have about 4,000-5,000 rounds through them in 2 years. When I first got mine my zero groups at 50yds had the holes touching. Now, I could not get my to hold less than 4" at 25 yards of a benchrest...I had other shooters attempt to zero it w/ similar results...is this related to head space??? Were you having the primer blowing from the start or did it start later? I'm sorry that I did not check back sooner to see your post. I firmly believe that the guns with problems were all .223 chambers. I recently used a neck & throat reamer made by Ned Christianson of Michi-Guns on six of the problem uppers and saw immediate MV drops to more normal levels. In recent correspondence with Tweak he said that he has seen more than one manufacturer mess up an order which are supposed to be NATO chambers and deliver .223 chambers and when the complaints start, blame the ammo rather than fix the problem. Please remember that Headspace is measured from the base of the cartridge case to a spot on the shoulder. That dimension rarely changes and has nothing to do with the neck of the cartridge. The real question/problem area is the freebore and where the bullet engages the rifling in the throat. |
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wrecktech
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Posted: 1/10/2009 12:08:54 AM
Originally Posted By BikerNut:
Not to highjack this topic... but I have a question about reloading the brass. The first 70-80 rounds out of my new AR exhibited the same overpressure marks on the case heads, just like the ones shown in the photos at the top of page 2 of this thread. I'll need to test the gun a bit more, try some different brands of ammo, see if the problem continues, etc. Absolutely no problems with ejection or feeding, though. However, all my new empty Lake City brass has these same marks on the case head. Is it safe to reload these, or should I kiss them goodbye? First some questions... What kind of ammo? XM-193, Remington UMC or something in .223? Do you know what kind of barrel you are supposed to have? Do you have access to a chronograph? If so check the MV ASAP. |
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Posted: 1/13/2009 5:34:21 PM
Originally Posted By wrecktech:
First some questions... What kind of ammo? XM-193, Remington UMC or something in .223? Do you know what kind of barrel you are supposed to have? Do you have access to a chronograph? If so check the MV ASAP. I was shooting Federal XM193 Lake City rounds with NATO headstamp. My DPMS is supposed to be a 5.56 chambered gun, and is marked "5.56" on the receiver and on the barrel. The empties had pretty noticeable pressure marks on the bottoms: indents from the bolt face and stress marks from the extractor. They also had light vertical scratches along the case walls. Overall, it looked like the cases were still a bit tight in the chamber while the extractor was trying to cycle them out. YET... absolutely no hangups in feeding or extracting. Every round went boom and the brass went flying. Some people have told me that, since it's a new gun, it may need to cycle a few hundred rounds to smooth out the chamber, and that it wasn't anything to worry about. So I'm not going to worry about it until I feed it more ammo. If it's still doing this after another hundred rounds, I'm going to try feeding it some plain old commercial .223 and see what happens. If it's stressing out on NATO ammo but cool with commercial .223, then I'll send it back to DPMS and have it checked. And likewise if it's gouging the cases on commercial ammo, too, since that would be an obvious overpressure issue. But my question remains: is this brass safe to reload? Can I take a small file to take the nicks of the rims and resize the brass and expect it to feed and function normally? |
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wrecktech
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Posted: 1/19/2009 1:47:38 PM
Originally Posted By BikerNut:
I was shooting Federal XM193 Lake City rounds with NATO headstamp. My DPMS is supposed to be a 5.56 chambered gun, and is marked "5.56" on the receiver and on the barrel. The empties had pretty noticeable pressure marks on the bottoms: indents from the bolt face and stress marks from the extractor. They also had light vertical scratches along the case walls. Overall, it looked like the cases were still a bit tight in the chamber while the extractor was trying to cycle them out. I misunderstood your question. I thought you were blowing primers with pressure signs. I'm sorry but I know nothing about reloading 5.56 brass. Have you tried asking your question in the reloading area? |
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Posted: 7/20/2009 3:08:14 AM
Not related to the problems here but, I have seen heavy crimps and excess oil in the chamber and bore cause high pressure signs also.
Almost every M193 and 855 load I have fired in the last 15 years has shown swipes but I have never had a primer fall out. |
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Posted: 7/12/2010 1:55:07 AM
Originally Posted By wrecktech:
Okay here goes the latest details: Headspace Check: Forster .223 Go Gauge 1.4636 - Closes with no problem Forster .223 No-Go Gauge 1.4666 - Closes with no problem Forster .223 Field Gauge 1.4696 - Resisted closing but then popped closed and opened without any problem with charging handle. ?????? .223 (Max-Field) 1.4736 - Would not close IIRC, All the gauges were purchased from Brownell's Suspect Gun: Armalite M15A2 5.56 Cal. .223 Ammo Test (Win. USA223R1) 70 Deg. / 15' from muzzle / Lo: 3011.93 Hi: 3043.74 Avg: 3024.37 No malfunctions of any kind in all rounds fired! No evidence of pressure marks on the case bases / primers and no raised primers visible. XM193 (Lot 39) Lo: 3342.99 Hi: 3371.86 (Blew primer on this shot) Avg: 3356.66 Comparison Gun: Styer AUG 16" ".223" XM-193 (Lot 39) Lo: 3112.62 Hi: 3153.16 Avg: 3132.81 (This AUG is known to take 5.56 without a problem.) My testing partner and I pretty much agree now that the M15A2 is probably a .223 chamber even though the barrel was replaced by the manufacturer shortly after a batch purchase resulted in troubles with every gun bought in the group. Why the gun has not had problems in the past two years and is now acting up remains a mystery. Please Tell me you are not Putting Head space gauges into a Fully assembled Weapon and allowing the mainspring tension to drive the bolt home??? 
Especially when the No Go Gauge did not want to close and then Closed...  ...
You should have used only Slight Finger pressure on an Disassembled Flawlessly cleaned gun... That's all you need to know if the gauges go or not... NO hard pressure... you are forcing very closely fitting HARDENED Gauges into the Chamber... not good my friend. You Can Ruin Guns doing that. |
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Posted: 5/8/2012 1:38:28 PM
I just ran across this thread because I jammed up my rifle yesterday and it turned out to be a smashed up spent primer down in chamber hiding behind the locking lugs.
This is the 2nd time this has happened to me in about 2000 rounds, the first time the primer fell down into my trigger assembly. I have a Ruger SR-556 so it is definitely chambered for 5.56. I bought several 500 and 1000 round boxes of Federal XM-193 and it is mostly all I shoot. Can I assume since the problem is infrequent, it is likely just the ammo and no fault of my rifle? |
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Posted: 6/26/2012 6:08:35 PM
Below, normal chamber pressure and the high stress points in red and yellow. (case stretching)
Below, excessive high pressure caused the base of the case to expand enlarging the primer pocket allowing the primer to fall or pop out of the primer pocket. 
Without pressure measuring equipment you can measure the base of the case with a micrometer and when this cartridge is fired if the base diameter increases more than .001 (one thousandths) it is a sign of excess pressure.  |
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Posted: 10/16/2012 12:33:20 PM
Haven't posted here in years, and we know we'll be looked upon with disdain due to the type of rifle we specialize in and work on, (we do work on ARs occasionally) but this came across my 'puter the other day and wondered if any here had read it. (?) Gun Digest Article
And clicking on the pic of the "5.56 Reamer" and ".223/5.56? gage" allows you to read more info on this guys answer to the pressure problem, on his site: m-guns Thoughts, questions, comments? |
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FMD
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Posted: 10/16/2012 2:49:06 PM
[Last Edit: 10/16/2012 3:00:38 PM by FMD]
We're not *all* snobs...
Tolerance stacking, both in head space/throat erosion and initial dimensions due to tool wear, can lead to bad, bad stuff happening. It seems to happen more in ARs due to the caliber and the ubiquitous nature of the gun. |
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Posted: 10/17/2012 11:53:26 AM
We're not *all* snobs... 
We used the "gage" and checked a S&W M&P15 yesterday that was marked 5.56 and it truly was. Then I checked a SP-1 that was marked on the barrel, "0 MP 5.56 NATO 1/7" and it was Not 5.56 but actually the smaller/shorter .223. Guess we'll find out what other brands are in time. |
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