need advice - AR15 Kaboom
- Thread starter darkgael
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stagpanther
New member
I'm thinking purely from the physics point of view something had to cause a huge spike in directed pressure to blow up an upper. Googling for this reveals that it seems to happen quite often--though I did notice there seems to be a few occurrences of hand-loads with relatively fast powders often being used at the time of failure. 2460 is typically quite fast for 223 and more usually associated with bigger cases like 308. I still think a chambering mishap, resulting in bullet push-back and possibly slightly out of battery (maybe even headspace tolerance had been "pushed out" over time and use) enabled peak pressures to spike way beyond normal pressures--and the case let go at the head before the bullet (obviously). The fact the bullet actually still fired and yet the pressures blew the upper up indicates tremendous pressure spike.
Found this at arf https://www.ar15.com/archive/topic.html? b=3&f=118&t=576463 and it looks like similar failure mechanics.
Found this at arf https://www.ar15.com/archive/topic.html? b=3&f=118&t=576463 and it looks like similar failure mechanics.
"2460 is typically quite fast for 223 and more usually associated with bigger cases like 308."
I think you have that bass-ackwards.
2460 IS slower than many recommended .223 powders "and more usually associated with bigger cases like 308."
It might be suitable for the heavier/longer .223 bullets(above 60 grains) but I don't load heavy bullets so don't really know about the performance.
At this point, everything is guess work but I'm really interested in the outcome regardless of if my guess is right or wrong. There may be some very important safety issues involved that need to be presented.
I think you have that bass-ackwards.
2460 IS slower than many recommended .223 powders "and more usually associated with bigger cases like 308."
It might be suitable for the heavier/longer .223 bullets(above 60 grains) but I don't load heavy bullets so don't really know about the performance.
At this point, everything is guess work but I'm really interested in the outcome regardless of if my guess is right or wrong. There may be some very important safety issues involved that need to be presented.
stagpanther
New member
Agreed--slower than some typical small cartridge rifle powders--but still a relatively fast powder for a rifle case especially with a small case capacity. Regardless of which direction the alignment my rear-end may be attached--I believe that there is a strong possibility that the compacting of a small spherical powder in a strong load was a factor in this failure. I put all the pieces together in my mind--223 brass, thinnish primers, hot charge, hand-loaded long bullets and a red flag goes up. But as you say I could be totally wrong.
stagpanther
New member
My apologies for thinking that you may have possibly had a bullet set-back if you are certain that was not a factor--just was trying to help.
1. CIP/military and SAMMI/Civ pressures are nearly identical. The MilSpec pressure is measured at/with a different case location/method.
https://ballistictools.com/articles/5.56-vs-.223-myths-and-facts.php
2. I'm going with the bullet Setback-on-Feeding theory. Given the OP's care/experience, and the highly unlikely probability of missing what is effectively a full case of 2460... AND the bolt now locked (even partially), that's the only thing that fits all the factors leading to catastrophic failure w/ normal brass. (shoving that bullet back 1/3" yield ~90,000 psi)
~~~~~~~~~~~~~~~~
postscript: Been There.... when it happened next to me... but more likely a loading problem:
8/23/2015
REPORT TO RANGE SAFETY
Today I was standing at a 45degr angle to the #4 shooting table at our local range reloading a Smith (50 cal/BP) carbine when I heard an unusually loud report from the #5 table next to me on the right.
I simultaneously felt a very hard impact on my right collarbone, so hard that I immediately put my hand up to the area and for awhile expected to feel liquid coming through the shirt. (As it was/is, I have a red-purple/plasma-weeping contusion about the size of a silver dollar.) At the same time I moved over to the #5 table where the shooter was standing up and back from a tricked-out Rock River AR-15 and looking at the magazine blown out in pieces on the table. Also on the table were several live rounds with distorted shoulders and bullets pushed at least halfway back into the cases from apparent misfeeds.
The rifle itself was still smoking a bit; the bolt carrier was jammed 1/3 of the way open; the bolt itself was extended forward from the carrier and locked into the receiver lugs; the receiver rails were bulged about a 1/4" out on each side; the receiver ring itself was cracked from the ejection port up to/past the lugs about an inch; ... and the bolt release on the left side was blown off/missing (having apparently hit me on its way down the firing line to the left). The shooter had no idea what had happened or why.
Looking at the distorted cartridges on the table it was apparent he'd been having feed problems with ammunition he had reloaded. Looking at the bullets shoved back into the case I mentioned that he'd likely had a feed malfunction/blowout where the bullet had been shoved all the way into the case before ignition. That didn't seem to register. The Range Safety officer was on the scene at this point and after ascertaining that the shooter has no injuries, asked what powder he'd been using. His answer was "1048". The Ranger Office offered that there was no "1048 powder"... and might it have been '748'? The shooter said he didn't know, but that "... it was in a green bottle."
Now the only powder I know that comes in a Green bottle potentially suitable for 223 is the newer IMR 4166, but no matter.... I asked him what load he was using so I could run a pressure simulation for a bullet fully jammed into the case and he replied "...well its a progressive but I don't think I have doubled charged it..., but [he thought] it was about 13** grains."
Hearing that, it was obvious I needed to bow out of the conversation and let the Range Officers handle it -- until I saw the shooter trying to pry open the jammed bolt carried with a screw driver levered against the front of the ejection port. I suggested that the bolt itself was completely locked into the receiver's locking lugs and that no amount of prying on the carrier would do anything but bend the ejection port edges and mangle the bolt carrier.... and that he probably wanted to ship things undamaged back to Rock River for a failure analysis... But he wasn't in the receive mode at that point.
The Range Officers gently suggested he pack things up, and he did.
I could start ticking things off on my fingers here... but I'll simply say that had I taken a normal rifle to the range I would have been sitting head level/temple exposed to that flying bolt stop.
But God sent me there with a Smith today... so I'd be standing when things came apart at the seams.
meh
postscript: I've heard that IMR-4166 is similar to 4064 burn performance, so I loaded up QuickLoad with a 55ksi/**26gr load of 4064 and then shoved the bullet back into the case all the way: 105-110,000psi. Shooter at table #5 needs to offer a novena to Gene Stoner next Sunday.
postpostscript: The Shooter was never anything but calm/confused and reasonable to both myself and the range officers. But it was obvious he wasn't quite totally connected with things from start to finish.
https://ballistictools.com/articles/5.56-vs-.223-myths-and-facts.php
2. I'm going with the bullet Setback-on-Feeding theory. Given the OP's care/experience, and the highly unlikely probability of missing what is effectively a full case of 2460... AND the bolt now locked (even partially), that's the only thing that fits all the factors leading to catastrophic failure w/ normal brass. (shoving that bullet back 1/3" yield ~90,000 psi)
~~~~~~~~~~~~~~~~
postscript: Been There.... when it happened next to me... but more likely a loading problem:
8/23/2015
REPORT TO RANGE SAFETY
Today I was standing at a 45degr angle to the #4 shooting table at our local range reloading a Smith (50 cal/BP) carbine when I heard an unusually loud report from the #5 table next to me on the right.
I simultaneously felt a very hard impact on my right collarbone, so hard that I immediately put my hand up to the area and for awhile expected to feel liquid coming through the shirt. (As it was/is, I have a red-purple/plasma-weeping contusion about the size of a silver dollar.) At the same time I moved over to the #5 table where the shooter was standing up and back from a tricked-out Rock River AR-15 and looking at the magazine blown out in pieces on the table. Also on the table were several live rounds with distorted shoulders and bullets pushed at least halfway back into the cases from apparent misfeeds.
The rifle itself was still smoking a bit; the bolt carrier was jammed 1/3 of the way open; the bolt itself was extended forward from the carrier and locked into the receiver lugs; the receiver rails were bulged about a 1/4" out on each side; the receiver ring itself was cracked from the ejection port up to/past the lugs about an inch; ... and the bolt release on the left side was blown off/missing (having apparently hit me on its way down the firing line to the left). The shooter had no idea what had happened or why.
Looking at the distorted cartridges on the table it was apparent he'd been having feed problems with ammunition he had reloaded. Looking at the bullets shoved back into the case I mentioned that he'd likely had a feed malfunction/blowout where the bullet had been shoved all the way into the case before ignition. That didn't seem to register. The Range Safety officer was on the scene at this point and after ascertaining that the shooter has no injuries, asked what powder he'd been using. His answer was "1048". The Ranger Office offered that there was no "1048 powder"... and might it have been '748'? The shooter said he didn't know, but that "... it was in a green bottle."
Now the only powder I know that comes in a Green bottle potentially suitable for 223 is the newer IMR 4166, but no matter.... I asked him what load he was using so I could run a pressure simulation for a bullet fully jammed into the case and he replied "...well its a progressive but I don't think I have doubled charged it..., but [he thought] it was about 13** grains."
Hearing that, it was obvious I needed to bow out of the conversation and let the Range Officers handle it -- until I saw the shooter trying to pry open the jammed bolt carried with a screw driver levered against the front of the ejection port. I suggested that the bolt itself was completely locked into the receiver's locking lugs and that no amount of prying on the carrier would do anything but bend the ejection port edges and mangle the bolt carrier.... and that he probably wanted to ship things undamaged back to Rock River for a failure analysis... But he wasn't in the receive mode at that point.
The Range Officers gently suggested he pack things up, and he did.
I could start ticking things off on my fingers here... but I'll simply say that had I taken a normal rifle to the range I would have been sitting head level/temple exposed to that flying bolt stop.
But God sent me there with a Smith today... so I'd be standing when things came apart at the seams.
meh
postscript: I've heard that IMR-4166 is similar to 4064 burn performance, so I loaded up QuickLoad with a 55ksi/**26gr load of 4064 and then shoved the bullet back into the case all the way: 105-110,000psi. Shooter at table #5 needs to offer a novena to Gene Stoner next Sunday.
postpostscript: The Shooter was never anything but calm/confused and reasonable to both myself and the range officers. But it was obvious he wasn't quite totally connected with things from start to finish.
According to the Western Podwers reloading info using 2460 in .223 with 69 GR Sierras the powder charge range is 21.1 to 23.4 GR, with the max at a pressure of 54,250. COAL is 2.245.
I will be interested in what you find. I had a similar episode with my Ruger SR 556. I fired a cartridge it blew out the magazine, locked the bolt. I had to use a brass punch and hammer to get the bolt loose. The cartridge case head had blown out. It bent the extractor which had to be replaced. The brass pieces that were blown out locked up the bolt. I saved that cartridge as a reminder to check cases more closely before reloading. It scared me, luckily no personal harm caused.
My case was a once fired in my gun from factory ammo. I read that yours was fresh.
I will be interested in what you find. I had a similar episode with my Ruger SR 556. I fired a cartridge it blew out the magazine, locked the bolt. I had to use a brass punch and hammer to get the bolt loose. The cartridge case head had blown out. It bent the extractor which had to be replaced. The brass pieces that were blown out locked up the bolt. I saved that cartridge as a reminder to check cases more closely before reloading. It scared me, luckily no personal harm caused.
My case was a once fired in my gun from factory ammo. I read that yours was fresh.
Loads
Reading through the repeated references to 23.4 grains of 2460 as a max load with the 69 grain MatchKing makes me think about how loads change over the years.
Accurate reduced the max since the publication of their number two loading guide (24.7 max at 2.25" Oal and 51.8kpsi) which is the one that I have. The powder is contemporary with the manual (and is in good condition).
Sierra's edition V manual has 24.5 max with that bullet.
Lyman #48 has 25.0 as max (49.3kcup)
Hornady does not spec 2460 for a 69 though they do spec the faster 2230 with 24.2 grains for a 68 gr. Bullet. FYI Only...I did not extrapolate from that data.
Speer #13 lists 23.5 as max. I did not look at the Speer manual until after this incident.
This data is what leads me to believe that the load was safe and that bullet setback is the likely culprit as opposed to any other over pressure situation.
Reading through the repeated references to 23.4 grains of 2460 as a max load with the 69 grain MatchKing makes me think about how loads change over the years.
Accurate reduced the max since the publication of their number two loading guide (24.7 max at 2.25" Oal and 51.8kpsi) which is the one that I have. The powder is contemporary with the manual (and is in good condition).
Sierra's edition V manual has 24.5 max with that bullet.
Lyman #48 has 25.0 as max (49.3kcup)
Hornady does not spec 2460 for a 69 though they do spec the faster 2230 with 24.2 grains for a 68 gr. Bullet. FYI Only...I did not extrapolate from that data.
Speer #13 lists 23.5 as max. I did not look at the Speer manual until after this incident.
This data is what leads me to believe that the load was safe and that bullet setback is the likely culprit as opposed to any other over pressure situation.
stagpanther
New member
I checked my Lyman's #29 and you are right--they show that max load for 2460, though I occasionally find "off the chart" loads in other manuals as well.
Something else occurred to me--do you regularly check your hand-load cartridges for engagement to lands, as well as shoulder set-back on your fired cases?
I commonly find that fired cases from an AR require the shoulders to be knocked back .002 or .003. I could see that if your shoulder datum is far forward enough--that could possibly contribute to out-of-battery situation. Depending on the ogive of the bullet and the chamber, it's also possible the bullet could be engaging the lands and forcing a set-back. Because you have a target model it might be it was designed with shorter free-bore, or maybe even throat erosion over time allowed the cartridge to be forced further into the lands.
Anyways, this thread is going to make me check my cartridges and chambers more often.
Something else occurred to me--do you regularly check your hand-load cartridges for engagement to lands, as well as shoulder set-back on your fired cases?
I commonly find that fired cases from an AR require the shoulders to be knocked back .002 or .003. I could see that if your shoulder datum is far forward enough--that could possibly contribute to out-of-battery situation. Depending on the ogive of the bullet and the chamber, it's also possible the bullet could be engaging the lands and forcing a set-back. Because you have a target model it might be it was designed with shorter free-bore, or maybe even throat erosion over time allowed the cartridge to be forced further into the lands.
Anyways, this thread is going to make me check my cartridges and chambers more often.
AR
Finally back home.
Separated the upper from the lower.
What appeared to be a crack in the lower in an earlier picture must have been something on the gun. There is no crack.
Pictures: looking down onto the bolt. It appears to be about five degrees from disengaging. Any suggestions about how I might get that to turn that little bit?
Finally back home.
Separated the upper from the lower.
What appeared to be a crack in the lower in an earlier picture must have been something on the gun. There is no crack.
Pictures: looking down onto the bolt. It appears to be about five degrees from disengaging. Any suggestions about how I might get that to turn that little bit?
stagpanther
New member
That's a tough one--though if it were me I would automatically assume the chamber and barrel were over-pressured and were a lost cause, so maybe "invasive surgery" is in order.
This was not an out of battery kaboom (The bolt is effectively engaged.) It is instead a catastrophic pressure failure.
Given the load -- even at max -- could not produce that kind of pressure, I'm still going with the bullet being shoved fully back into the case upon chambering.
Given the load -- even at max -- could not produce that kind of pressure, I'm still going with the bullet being shoved fully back into the case upon chambering.
I concede I am not knowledgable enough to say how much pressure increase will occur with bullet setback in a rifle.
I'm setting that aside,with a shrug.I don't know.
How physically full is the cartridge case with powder at the charge weight used?
It has been my experience that with the powders I use(not 2460) when I am at a max or near max load the powder fill is to the base of the neck.Sometimes,even up into the neck a bit.I recall using a drop tube with one load.
A 69 gr boat tail at 2.260 intrudes into the powder space.You can compress powder some.A little bit.But after that,it becomes pretty solid.
So,I wonder how far a bullet will be set back by the bolt coming forward given the neck tension plus the support of the powder against the bullet base.
I'm not saying I know the answer.What is the load density of the OP's load?
What could possibly be: Insufficient shoulder setback in sizing,and the "grey zone" where tolerances may permit firing in a partial battery situation.Maybe.And the loads were such,that the smaller surface area of steel allowed setback.Partial bolt failure.Maybe.
The extractor was still in place.The receiver does not look like there was a major case fail.There is not evidence of gas blowing things apart.There is,IMO,NOT a catastrophic cartridge case failure.
And,if this rifle were mechanically sound,with the lugs fully locked,the lockup(bolt and receiver extension lugs) can take ANY OVERPRESSURE short of case failure.
Bullet setback,overload,etc increasing pressure don't add up for me if the case did not blow out.Had the case blown,you would see it at the extractor.
It still bothers me that the gas rings are visible through the hole in the bolt carrier with the bolt fully extended.That is approx 1/8 in different in length than my intact BCG.
The OP's bolt appears to be about 1/8 in longer than my intact bolt.
Which leads me to believe the OP's bolt is not intact.
Mystery!!
I'm setting that aside,with a shrug.I don't know.
How physically full is the cartridge case with powder at the charge weight used?
It has been my experience that with the powders I use(not 2460) when I am at a max or near max load the powder fill is to the base of the neck.Sometimes,even up into the neck a bit.I recall using a drop tube with one load.
A 69 gr boat tail at 2.260 intrudes into the powder space.You can compress powder some.A little bit.But after that,it becomes pretty solid.
So,I wonder how far a bullet will be set back by the bolt coming forward given the neck tension plus the support of the powder against the bullet base.
I'm not saying I know the answer.What is the load density of the OP's load?
What could possibly be: Insufficient shoulder setback in sizing,and the "grey zone" where tolerances may permit firing in a partial battery situation.Maybe.And the loads were such,that the smaller surface area of steel allowed setback.Partial bolt failure.Maybe.
The extractor was still in place.The receiver does not look like there was a major case fail.There is not evidence of gas blowing things apart.There is,IMO,NOT a catastrophic cartridge case failure.
And,if this rifle were mechanically sound,with the lugs fully locked,the lockup(bolt and receiver extension lugs) can take ANY OVERPRESSURE short of case failure.
Bullet setback,overload,etc increasing pressure don't add up for me if the case did not blow out.Had the case blown,you would see it at the extractor.
It still bothers me that the gas rings are visible through the hole in the bolt carrier with the bolt fully extended.That is approx 1/8 in different in length than my intact BCG.
The OP's bolt appears to be about 1/8 in longer than my intact bolt.
Which leads me to believe the OP's bolt is not intact.
Mystery!!
Last edited:
See paragraph 2:
http://thefiringline.com/forums/showpost.php?p=6379082&postcount=49
Running the actual load/charge/bullet in QuickLoad, Setback can hit 100ski in a hurry.
Nothing else satisfactorily explains the conditions/results as described by the OP.
http://thefiringline.com/forums/showpost.php?p=6379082&postcount=49
Running the actual load/charge/bullet in QuickLoad, Setback can hit 100ski in a hurry.
Nothing else satisfactorily explains the conditions/results as described by the OP.
You might be right.I am sure I do not know the answer.
Once again,what bothers me,if the pressure hit 100,000 psi,the case would have blown.Correct me,but probably by 80,000 the case would have blown.
Had the case blown,the receivers would have ballooned some,and the extractor would be gone.
Without evidence of blown case/gas destruction,I donot see this wreck as primarily about pressure.
I see it as a mechanical failure.The gas remained contained.
I'm open to being wrong.I have a hard time getting past that part.
Once again,what bothers me,if the pressure hit 100,000 psi,the case would have blown.Correct me,but probably by 80,000 the case would have blown.
Had the case blown,the receivers would have ballooned some,and the extractor would be gone.
Without evidence of blown case/gas destruction,I donot see this wreck as primarily about pressure.
I see it as a mechanical failure.The gas remained contained.
I'm open to being wrong.I have a hard time getting past that part.
stagpanther
New member
Maybe if you somehow get the bolt disengaged from the carrier you can remove the barrel nut and get the assembly out--might be easier to work with then--but that is internet amateur advice rather than having a pro gunsmith. : ) Either way--I'd be very interested to see what your chamber is like--would be worth it to do a cast and see what the measurements are and if that might have possibly been a factor.