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Posted: 3/6/2005 4:49:40 AM EDT
ouch.....i hate it when this happens...
what do i need to check on this gun, both dimensionally and otherwise to try and determine WHY it happened....BM bolt on Colt bolt carrier....20-inch h-bar bushy barrel.... TIA 
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Posted: 3/6/2005 5:07:32 AM EDT
[#1]
tag - extractor broken too ?
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Posted: 3/6/2005 5:10:55 AM EDT
[#2]
nope...extractor intact....
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Posted: 3/6/2005 9:19:10 AM EDT
[#3]
Improper heat treat? Might be why a bolt that is Magnetic Particle inspected is better. BM only randomly sample MPC's their bolts....
Mick |
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Posted: 3/6/2005 10:15:18 AM EDT
[#4]
put another bolt/carrier in today and fired 25 test rounds. had 3 cases that blew out the primers (win 55gr fmj white box). i'd say its a case of excessive chamber pressures....for some reason...
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Posted: 3/7/2005 3:29:14 AM EDT
[#5]
checked the MAX HS dim?
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Posted: 3/7/2005 3:42:06 AM EDT
[#6]
Ditto, I'd be checking the "head-spacing" on my rifle. Mike |
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Posted: 3/7/2005 11:10:33 AM EDT
[#7]
Using same ammo with new bolt that you shot with the broken bolt? Was the primers showing overpressure before the bolt broke?
Shok |
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Posted: 3/7/2005 3:29:04 PM EDT
[#8]
Tweak & Mr_Wilson ~ thanks....checked barrel for HS and it checks out fine.
QShock ~ using same ammo before bolt broke, but dont recall any blown primers......humm.....interesting.... 
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Posted: 3/8/2005 12:23:09 AM EDT
[#9]
so it wasn't the bolt getting a running start on the lugs of the extension.
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Posted: 3/8/2005 12:44:28 AM EDT
[#10]
bolt is on its way back to the factory to see if they have any comments. if so, i'll post 'em right here dudes......
i need to run some different ammo thru the gun and see if i continue to get blown primers. if HS is ok, what else could be causing that kind of chamber pressure? doesnt make sense to me. manual insertion of bolt/carrier feels smooth. i dont get it... |
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Posted: 3/8/2005 3:09:09 AM EDT
[#11]
are you seeing signs of high pressure on the base of the case?
did the rifle work before the kB? |
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Posted: 3/8/2005 5:39:13 AM EDT
[#12]
I didn't see a section in ammo oracle on signs of overpressure to refer you to. Popping primers is not the only sign of overpressure. Did any primers have holes? Exactly what ammo were you using?
Shok |
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Posted: 3/8/2005 6:12:30 AM EDT
[#13]
Personally Iv'e run into to latter case head problems when assembling short barreled (14" to 10") ar's for L/E personell. Seems that the head space needs to just about perfect or the guns rip case heads and blow primers. By perfect I mean you need to experiment with different bolts to find a match to your gun and chamber. Any gunsmith/armorer will tell you that even though the parts on the M-16/AR where designed to be mismatched for a field expediant repair it always doesn't work as easily as that. Also as has been mentioned Ammo can play a big role. One 12" gun I built would not run Win White Box but it ate everything else and S+B for practice and SS109 Surp for carry. Go No/Go and Field gauges can really help in bolt selection but they may not always be available and even if the bolt passes all the gauges.
Just my .02 GPK...out  
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Posted: 3/8/2005 6:48:40 AM EDT
[#14]
good info guys - thanks for the comebacks and questions.
was using winchester 3131 white box. i didnt notice any excessive pressure indications on the brass or on the bases of the cases. rifle worked good before the kb. no holes found in any of the primers, and they all looked pretty standard with regards to firing pin indentions.... i'm going to load up a few round of xm193 and see how it shoots here in an hour or so if i can get myself up to it....working graveyard shift this week and it's hell on the bod.... 
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Posted: 3/8/2005 7:28:52 AM EDT
[#15]
If you were useing Q3131 no "A" then I think you found your problem. |
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Posted: 3/8/2005 7:50:14 AM EDT
[#16]
am using Q3131A.....however.....
just ran 15 rounds thru with no problem....ya know, this kind of thing reminds me of troubleshooting those pesty "intermittant" problems i remember as a kid working on cars.....anyway... no blown primers this test run. pics of the win Q3131A casings (no blown primers this time)....  pics of xm193 casings....  pics of SS109 LC casings....  pics of all three....you guys with keen eyesight see anything out of the ordinary here? need to get to the range and run about a 1000 rounds thru it over the course of a day and see how it functions i suppose...... 
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Posted: 3/8/2005 10:24:31 AM EDT
[#17]
burnsome, check your q3131a lot #'s, there were several strings last summer/fall about bad lots
Problems reported with Lots: TD51 - Blown primer TK42 - Blown primer UF21 - Feeding problems UM11 - Failure to fire - bad primer? VA82 - Blown primer VA92 - Blown primer VE21 - No primer hole? VG41 – Blown primer, FTE VA82 and VA92 had the most complaints. Also please post what you hear back from Bushmaster about the bolt. |
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Posted: 3/8/2005 2:50:35 PM EDT
[#18]
case heads look fine. chamber might be oversize or brass is soft. tried other ammo?
is this a short barrel? |
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Posted: 3/8/2005 9:31:06 PM EDT
[#19]
GODBLESSTHEUSA - thanks for the tip there. i had no idea there was a problem with win white box. i'll check lot # of my stuff and report later today....
Tweak -- i might have some PMC laying around i can test run a few through....it is a 20-inch barrel. |
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Posted: 3/9/2005 3:34:52 AM EDT
[#20]
20" and you're running the standard spring and buffer?
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Posted: 3/9/2005 4:17:37 AM EDT
[#21]
Sorry if this is too off topic, but did Bushmaster ever ship CAST bolts?
The reason I ask is because I was looking at my BM supplied bolt(circa 1993?) recently, and the front of the locking lugs looked cast rather than machined. Some of those fired casings do look hot, notice how the brass has flowed into the ejector hole in the bolt face. Paladin |
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Posted: 3/9/2005 9:40:50 PM EDT
[#22]
tweak - yes sir..std buffer and spring....
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Posted: 3/10/2005 10:55:10 PM EDT
[#23]
oh shit, you're right paladin, definite sign of overpressure, I thought that mark was part of the stamp on first, and only, glance.
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Posted: 3/10/2005 11:17:23 PM EDT
[#24]
yup, that had me scratching my head and wondering why those marks were pronounced a bit more than i'm used to seeing.....
ok gents - so what could/would cause that kind of overpressure...? |
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Posted: 3/11/2005 8:11:05 AM EDT
[#25]
Winchester Q3131A, Lot PG51. I picked the two worst cases with that indication you guys spotted and here is a close-up.....
time for a new barrel? 
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Posted: 3/11/2005 10:02:00 AM EDT
[#26]
Still could have a bad lot. Check OAL maybe the bullet is seated too low.
Shok |
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Posted: 3/11/2005 10:20:49 AM EDT
[#27]
I'm sure I'll be corrected if I'm wrong but if the barrel headspaced fine with a new bolt AFTER the incident I'd think the chamber would be ok and there'd be no need to replace. Only other consideration is cracks in the chamber, throat, and barrel outside the chamber. Looks like the bolt is what took the brunt of the overpressure.
It seems that Q3131a is not to be trusted, which totally sucks as I have a couple of cases of it. |
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Posted: 3/12/2005 1:39:05 AM EDT
[#28]
just bad ammo unless the bore is too small or the chamber way short; sub GO HS or tight/short leade.
Whose barrel? first time firing that barrel? |
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Posted: 3/12/2005 1:41:56 AM EDT
[#29]
that sucks!
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Posted: 3/12/2005 9:34:15 AM EDT
[#30]
Just went through my ammo this A.M. - found 2 rounds of Q3131A with a .008" over 0 on an RCBS Precision Mic along with 10 rounds ( out of 500 ) of my reloads in .005"+ range . May be unrelated, I also found the ejector retaining pin to be very shiny on one end , so it was reseated equadistant in the bolt . Function tested all ammo ( NO firing pin ! ) and only oversized ammo failed chambering fully and ejecting |
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Posted: 3/12/2005 3:03:57 PM EDT
[#31]
tweak - good dam question sir....!
went looking at this barrel and, low and behold, there are no stamps anywhere on this barrel so i have no idea who the hell made it.....its a pre-1985 purchased item that was thrown in on another deal i was doing.... i think i'm going to cut my losses on this and get a new upper and/or barrel and go with the flow gents.... thanks all for the comebacks and stay safe out there... |
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Posted: 3/17/2005 7:46:51 AM EDT
[#32]
Ditch that barrel.... or have the chamber reamed to NATO spec if it aint chrome lined.... which I'll bet it aint.
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Posted: 3/17/2005 7:55:22 AM EDT
[#33]
i'm with ya sir.....
ditched it is !!!!! this kinda stuff is not worth messing with when ovepressure signs tell you to watch out..... have a new RRA upper on order..... |
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Posted: 3/17/2005 1:52:20 PM EDT
[#34]
Hey - you guys taught me a lesson - indirectly. I was always taught to look for squished primers. But then I was just reading that mil-spec primers are supposedly tougher than normal - so maybe they don't squish.
Of course, you also look at headstamps - and I realize now those ejector markings... Neat. Oh, sucks btw - Q3131A is supposedly hot but that's HOT! |
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Posted: 3/21/2005 5:32:46 PM EDT
[#35]
Congradulations on proof-load testing your bolt 15 times.
 Did that once with a 20 round box of '99 Q3131, 3200fps from a 16" barrel vs 3085fps for normal Q3131A, whee. :) |
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Posted: 3/21/2005 11:09:14 PM EDT
[#36]
you bet...
good reading courtesy of NorWester from another thread... www.reloadingpro.com/Case%20Conditions.htm |
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Posted: 3/22/2005 10:17:11 AM EDT
[#37]
that is a good thread! i just looked, i've got 15 boxes of winchester white box, five of which are q3131, no "a"...should i toss this stuff? or maybe break it down for components?hinking.gif
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Posted: 3/22/2005 10:24:31 AM EDT
[#38]
Only some of the '99 lots were bad so check the headstamp. Even if it is '99 that doesn't mean it's bad.. might want to put a couple rounds over a chronograph. |
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Posted: 3/27/2005 6:20:56 AM EDT
[#39]
I just have to ask as a point of reference.
Could this barrel be chambered for .223 and not 5.56? I have heard a lot of discussion regarding shooting 5.56 ammo in a .223 chamber will cause pressure problems. In fact my agency bought ten rifles a couple years ago and they all had to be rebarreled (under warranty) because they were .223 even though they were marked 5.56. We were having major problems with malffunctions and blown primers on brand new rifles shooting the Remington and Winchester generic 5.56 ammo. |
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Posted: 3/27/2005 2:19:08 PM EDT
[#40]
only in an extreme case.
who made your agency's barrels? |
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Posted: 3/28/2005 5:01:08 AM EDT
[#41]
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Posted: 3/28/2005 10:55:11 PM EDT
[#42]
were the barrels chromed?
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Posted: 3/29/2005 5:12:06 AM EDT
[#43]
With all the problems, the ten guns all went back to the factory once and then a tech from the factory came to our station and did the barrel change there. That much I did see as he also reset the front sight base on my personal gun that was canted off to the right. Since the barrel change, we now have several length barrels. Mostly 16" but some 18". Not noticeable unless you put them all side by side in a rack. |
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Posted: 3/30/2005 5:32:02 PM EDT
[#44]
just FYI
bushmaster delivered new bolt to me today. no comments, but just good customer service. thought it was worth mentioning.... |
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Posted: 3/30/2005 5:56:32 PM EDT
[#45]
+1 for Bushmaster Customer Service.
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