Kaboom :-\ . 223 pics and video

[adam_mac84]

https://youtu.be/e_qe5tCL4ew

Last stage of todays (small) 3 gun local match .

Probably 75 rounds deep into a 150 round batch that I had loaded for 223.

24 grains h335 (fills enough of case, cannot be a double charge)
-hopper only used for rifle powder, and was in the middle of the whole box I loaded
OAL 2.240 (crimped at cannelure, light to medium).
CCI primers
OAL checked with calipers following size/deprime, <1.755, chamber checked with Lyman case length headspace gauge
Loaded on Lee Turret Press
Checked with Lyman OAL loaded round chamber checker (the orange one) prior to putting in my ammo box after loading

On my computer, frame by frame, at the detonation, you can see bullet impact in the berm. After pulling bolt, barrel is clear. RO and I heard clean click, confirmed later by the video, thinking less likely squib. Unable to determine if the round that was cleared in FTF malfunction had a bullet in the casing. Too many loaded rounds on ground from people clearing the stage.

Of course, first question is always 'are they reloads'. Yes. But upon inspection by some people more knowledgable, they think possibly some sort of failure to fully go into battery (is not a fancy or $$ upper/bolt, Palmetto State Armory), causing detonation out of battery due to some less than ideal tolerances. Hard to say tho, cause gun has been through ~2k rounds

Was not a slam fire. I pulled the trigger.

PIcs coming from my phone so they aren't huge

Any thoughts on diagnosis? I want to obviously be sure things are less likely to happen again (after i beg my wife for the next 12 months to let me get a new rifle :(

[adam_mac84]

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[jonp]

Under recoil a bullet that sank into the casing too far due to a lighter than expected crimp causing too much jump.

[lightman]

I don't think that load of 335 would be overpressure enough with a deep seated bullet to do that. I'm thinking Skeettx may be on to something. Glad you were not hurt and hope you find the cause.

[skeettx]

I could not tell in the video, when you recharged the rifle, did you eject a loaded round?
Did the loaded round, now on the ground, have a bullet in it?
Or did the bullet remain in the barrel
Yes, in reading your original posting above.
I guess the only reason you will ever be able to offer is "It was Sunday!!"
Mike

p.s. I deleted the original posting as I wanted to study the video more.

[runfiverun]

I'm seeing too much pressure.
usually a bullet that falls in the case isn't enough to make that happen.
one that was shoved down there by another would.


I have only seen 3 other AR ka-booms, they all have followed a re-charge with the handle.
2 were in 3 gun competition.
1 was in the field.

[johnho]

That's a shame for sure. Two things come to mind. I use H335 behind a 69 but only use 22.5 grns. Hard to tell but that primer looks a bit pushed out but the indent from the firing pin looks normal. Other is maybe a crack at the base of the case you didn't see when reloading. Sure is a mess. Sorry.

[popper]

I'll swag it. Dirty chamber at shoulder and a poor carrier. Seen too many that have very little metal at the mag lip area. OOB fire. Case blew out through the feed ramp, took out extractor & bottom of carrier.

[MyFlatline]

Glad you weren't hurt bad...

[Moleman-]

With the case flowing into the ejector recess I'm going with a gross overpressure. Most likely caused by a squib round that you ejected as skeetex said. YouTube is full of similar videos.

[adam_mac84]

Thanks for the feedback guys!. I am disappointed for sure, but can save for another gun, I only have 2 hands for life, and 1 moneymaker (face). haha.

Forgot to state above, 55grain bullet . FMJ (Berrys)

Question, would the fact that during the detonation, the bullet did hit the berm mean anything? Could it have blown both bullets out if there had been one lodged in there? I can certainly see that as a cause, however, the bullet shouldn't be contacting the lands (2.260 do not impact either)

[skeettx]

Perhaps
And near you, the shooter, I would have looked for a primed/powdered case with no bullet.
Would have been close as it was not gas ejected from the gun.
Too late now, it was Sunday :)

[adam_mac84]

I did search. That place was right where everyone the whole day had 'unload and show clear'. So there was about 50 empty cases, and a handful of unfired rounds. Searching for the empty PRIMED unstruck case would have been the money find. I did not think about that however

Also, another piece of info on these rounds:
2801 FPS . probably not worth much

[Moleman-]

I've had two instances out of the same batch of some PMC M193 that popped the primer and sent the bullet just into the rifling. Dumped powder everywhere which was a big red flag that there was "some issue". The same thing happen with my buddy only he didn't realize the bullet was still in the barrel. He had tried to load another round but the unburnt powder luckily kept the bolt from closing. He asked me if I had a chamber brush which I did, but also checked the bore which was blocked.

[MaryB]

If it was a squib the barrel would show a bulge, shine a light down it and see if there is a low spot...

[jonp]

If it was a squib the barrel would show a bulge, shine a light down it and see if there is a low spot...

Thats what bothered me about the squib argument unless the squib was right in the throat

[rockrat]

i will take a SWAG. My theory: You had an uncharged round, so when the primer went off it pushed the bullet down in the throat area. You pulled the charging handle, chambering another round. You might have a bulge or you might not if the point of the newly chambered round was resting on the base of the bullet in the throat. Also, possible that when chambering the following round, the bullet in the chambering round hit the base of the bullet in the throat and the bolt didn't lock completely so you also had an OOBD along with pushing 110gr of bullets down the bore. Look on the video and see if maybe you have two bullet impacts on the shot.

Looks like maybe a new upper and bolt/carrier is in the future.

[vzerone]

adam_mac first I'm very happy that you weren't hurt! Okay...out of battery...in battery means that the bolt is close and locked up. Out of battery means it's not locked up and guess you could say open too. Now I guarantee you that if a 50k some round went off with almost all the case in the chamber and the bolt not locked, you'd been severely injured. Pretty rare bird for an AR to fire out of battery. I agree with some of the others that it wasn't a squib load. Like Mary B said there would have been a bulge in the barrel and I discount it stuck in the throat because the round that blew wouldn't have chambered enough to fire it. The case blew at the extractor area and the gas vented down the mag well as it has nowhere to go up to. It's one of those things that will keep you guessing for a long time to come. Who knows, perhaps might have even been a weak case. Most the AR kabooms I've seen the shooter walked away unscathed. Testimonial for the AR design.

Vince

[adam_mac84]

Good discussion guys, again, i appreciate it, and the lack of 'hey *******, you ***** up'. Cause, yes, I know that. Take safety very seriously.

Post mortem analysis of the remaining rounds in that mag. I did find an additional round that with what I would consider moderate pressure, would set all the way back in the case (not finger pressure, nose on the table and pushing in). Got word from a gunsmith (via photos), who also said overpressure. Based on this and the setback that I found on my post-analysis, I am taking my blame 100% and learning from it.

I have to measure the cases that I have (mixed brass), but on visual inspection the suspect (setback manually) case, seems to ahve thinner walls, so my crimping die wouldn't have compressed it as much, leaving the tension up to neck tension, which apparently wasn't enough on this particular cartridge.

Lessons learned.
No more mixed brass for me
Increased frequency of bullet setback (usually do every 25 off the press)
Investigate increasing crimp at cannelure
Investigate/measure plugs in sizing die for internal case mouth diameter.
I will likely take a short hiatus from the reloading game while I get this all figured out

I also would now like to find a cost effective way to measure bullet pull and bullet setback weights... any ideas?

Be safe out there reloaders!!!

[popper]

Look at the thickness of the broken steel at the bottom of the carrier!

[Tracy]

Looks like OOB to me. OOB would likely still drive the bullet out of the barrel and perhaps hit the backstop. And it wouldn't be driving the bcg back with 50K pressure because unsupported brass won't allow that much pressure to build.
The type of damage I'm seeing is completely consistent with out of battery ignition.

[runfiverun]

initially I thought OOB too.
but the bolt head has to rotate and come back into place for the firing pin to reach the primer.
that plus the brass around the mouth of the chamber.
the AR is pulling the case out of the chamber while the case is still under pressure, which would allow the case head blow out.
the projectile velocity could have been very slow while the bolt speed would be very high, even without the gas volume to push it rearward.

[M-Tecs]

In the video the you can't tell if you ejected brass when you manually cycled it but I would bet you did.

I am far from an expert on blown AR's but I have inspected and or repaired 9 or 10 that had blown. In addition to building ar service and match rifles I managed a machine shop and a nondestruction inspection shop. A couple of shops brought me stuff to inspect

One coworker blew two ar's on one prairie dog trip. He had just started using a Dillon swager and was collapsing the primer pockets so he had primers above flush and had slam fires. Only non-repairable damage was to the bolt. One was cause unkown but all the others happened after a stoppage and manually cycling a round.

Damage looked exactly like yours except the one cause unkown. That one was much more severe. Over the chamber 1/2 the barrel was blown off.

All the others had a bullet in the bore due to various reasons. Mostly no powder in the case but one was a long seated bullets. The bolt didn't close and shooter ejected the round racked another in and fired. In addition to loose powder in the action an unfired primed case was picked up.

Bolt carriers, bolts, cases and uppers failed just like yours.

As stated above oob is not possible from the hammer hitting the firing pin due to the design. OOB firings can be caused by high primers, broken firing pins or something acting as a firing pin. Out of tolerance part can also do it but I have yet to see or hear of parts that far out of spec.

Other than a life or death situations all malfunctions need to be inspected before chambering another round.

[M-Tecs]

On a side note I was out at the range and a shooter was having lots of failure to cycle/issue. I normally don't stick my nose into other people's business unless asked. I was testing a couple of match ar's

This shooter came over and asked for help. These were his first reloads since started turning necks. He did 100% cleanup on the necks and was using standard dies. The bullets would push into the case when chambered. I don't remember his load specifics but I do remember he was using TAC. Even with the bullets pushing in primers looked ok.

[M-Tecs]

I guess its why smart simple folks prefer a good bolt action.

Uncalled for and baseless.

[Three44s]

It strikes that the OP had two slugs traversing the barrel at once.

Glad he's alright!

Three 44s

[earlmck]

There is another possibility and I might even put it as a probability: your case was too long -- needed trimming. A too-long case that jams a bit into the leade and doesn't release the bullet easily can create amazingly high pressure. (yep, voice of experience here).

I just got done trimming a whole bushel of 223's because after just 4 (maybe 5) reloads one of my cases had grown so much that it stuck the case a bit in the chamber and fortunately didn't allow the bolt to close, so wouldn't fire. Most of my cases were still in spec but I had a few that were definitely too long. (Yeah, mixed range pick-up brass). I am old enough to know better -- kicking myself for not checking brass length earlier but sure glad that baby didn't fire or my rifle might have looked like yours.

[jonp]

"One coworker blew two ar's on one prairie dog trip. He had just started using a Dillon swager and was collapsing the primer pockets so he had primers above flush and had slam fires"

Loose primer pocket causing the primer to back out and a slam fire on the reloads?

[Lloyd Smale]

few things could cause it. Sometimes a bit of powder bridge in a measure and can drop with the next charge and yes you can overload a 223 with 335. Second is a squib but you would have know that because you would either have heard a primer go off or at least had to pull the charge handle a second time. My best guess is your gun fired without a round fully into the chamber. Either caused by brass that didn't size down enough or brass to long. I haven't seen an AR do it but ive seen a couple glocks go kaboom because of it. Another thing could be tired brass. If your brass was getting a bit old and stretched you could have had a case head separation. But that would probably not show flattened primers. Ive come to only use ammo in my ars that have been small base sized and trimmed after each firing and have had the primer pockets swaged. Guarantees they go in the chamber all the way reliably and wont slam fire due to a primer not being fully seated. Ive got a Dillon trimmer and swagger so it isn't much more work to guarantee reliability. I also have an led light mounted on my press over the powder drop station so that if a measure does bridge and drop to much its easy to see. ALLWAYS visually look at each round so that you notice any major difference in powder level in the case.

[M-Tecs]

"One coworker blew two ar's on one prairie dog trip. He had just started using a Dillon swager and was collapsing the primer pockets so he had primers above flush and had slam fires"

Loose primer pocket causing the primer to back out and a slam fire on the reloads?

No with the Dillon swager if you adjust the swager too deep you push material into the bottom of the primer pocket. This seems to only be an issue with 223 due to the small size of the internal support rod.

[M-Tecs]

For the folks that believe you can fire an ar out of battery take a primed case and try it. The bolt has to be fully rotated before the firing pin can reach the primer.

The video clearly shows and the OP stated he manual cycled the next round after an ftf. The bolt carrier was blown. That happens from massive over pressure.

In the early day of AR in highpower comp. AMU used a load that called "V8" for long range. The had to use LC prime and crimped brass. Brass was shot after one firing. Pressure was over 70,000 psi.

[bob208]

shooter error when shooting if the gun goes poof instead of bang stop and check the bore. do not load and fire another round and fire. you had a stuck bullet in the barrel.

[rockrat]

If not an OOB, then to me, the only other idea would be two bullets going down the bore. Pressure in the system was who knows how high and when the two bullets passed the gas port and the bolt started unlocking, the pressure was still so high that the case head was essentially sheared off when it became unsupported and the high pressure deposited the brass at the back of the chamber. So, a squib, followed by a normal round

[vzerone]

I see M-Tec is savy of the fire out of battery myth! Just not going to happen with an AR. The reason the carrier blew is due to escaped high pressure gas entering it. There isn't any firing pressure on a carrier. A carrier is just that..a carrier....it carries the bolt. Now when the rifle is functioning there is some stress on the cam bolt which the carrier is part of. Take a primed case (no powder no bullet please) place it in the chamber and let the bolt slam shut on it. See how many times you can do that. I'll bet till you get tired of doing it. That slam fire story about the firing pin causing it is a myth. Now a high primer might just do it. The primer in that case head just doesn't show massive pressure. I still feel the case let go. Try another test. Prime a case and load a bullet WITHOUT any powder and just see if the primer drives the bullet out of the case and how far. An AR bolt/carrier group just does not have enough oomph to chamber a cartridge if there is a bullet in the throat that the new rounds bullet may touch, unless you have no neck tension at all on your loaded round. Cardinal rule: Whenever a round doesn't fire ALWAY check your firearm especially the bore to make sure there's not a bullet stuck in it.

[JonB_in_Glencoe]

H335 is a Hodgdon powder, obviously. The Hodgdon reloading site shows 3 different 55 bullets for 223, none of which are 55 FMJ designs. The OPs load of 24 grains exceeds max for 2 of these 3 bullets.

>>>SNIP
That's interesting, I don't doubt you, but I recall it being more, as I've used H335.

I dug into a few manuals.
Lyman 49th Has 27gr as Max for the only 55gr jacketed bullet listed.
Nick Harvey's manual also lists 27gr as MAX.
Hodgdon paper manual lists only one 55gr jacketed bullet and Max was 25.3gr.

[Larry Gibson]

Did not fire out of battery or bolt and bolt carrier would have been blown to the rear.

OP had a bore obstruction. Watch the sequence of events in the video. OP pulled the trigger, just a click, no bang, no recoil. OP Ejected the case and next round....Ka-boomed..... the bullet from the previous FTF round that was cleared probably had no powder and the primer drove the bullet into the leade where it stuck. Next chambered round had it's bullet pushed back into the case when it was chambered. Obviously 23 gr H335 is a gross overload for 110 gr of bullet in a .223.

Any time you have a misfire (FTF) like that, in a match or not, and you can't tell if the ejected case still has the bullet in it you should stop and check the bore. Yes, you will lose the match but better that than lose the rifle and perhaps some part of yourself........

The RO should have stopped the OP on the misfire. Numerous 3 gun matches I'm aware of have included mandatory stopping the shooter if a FTF round can not be seen to still have a bullet in it......this example is the classic reason why........

[popper]

Just not going to happen with an AR. And when YOU have had one - OOB - , you will believe that even the design can be beat. It is NOT a myth. I agree that you MUST do a chamber check on a FTF in ANY gun.

[vzerone]

If you fire out of battery, and Mr Gibson agreed with me, that carrier/bolt group is going back and possibly driving itself, the buffer and spring, and maybe the lower receiver tube extension THROUGH your shoulder. Anytime that doesn't happen, you don't have an out of battery firing. The AR firing pin barely protrudes from the bolt face and it doesn't do so until the bolt is in full battery and fully rotated. In addition, and some of you many not know this, the leading edge of the slot in the bottom of the carrier is also designed so that if the bolt isn't in full battery it hits the hammer and prevents it from striking the firing pin.

[vzerone]

If the op had been shooting the he stated and he didn't mention anything about them being hot or extremely flat primer and swelled web area of the case I highly doubt it was a overload. Again Mr Gibson stated a H335 load with a 110 grain bullet for comparison. I'll also bet my gun safes that the op's rifle has a 5.56 NATO chamber rather then an honest 223 Remington chamber and is more forgiving with loads that are for the 223 Remington.

I highly doubt also that the his bolt is 9310 steel. It's more then likely the standard carpenter steel.

Mr Gibson and I are in the same boat on this incident.

[vzerone]

Beg your pardon Mr. Beeman, I was among the first, if not the first, to mention it wasn't an out of battery occurence back in post #18. I too am more then familiar with the mechanics of the AR. I also didn't point you out on anything, but yet you seem to think so.

Assembling an AR doesn't mean you know how they function. They really aren't a plug n play. More then likely a very high percentage of the time the rifle will function, but when it doesn't and something is the matter with it, that's where the novice gets lost.

I may take my AR 15 out of the safe and just load cartridges with no primers, that is just the bullet and live primer and fire the first one to see how far in the rifling the primer pushes the bullet. There are many things dependent on how far that bullet will go. Just to mention a couple neck tension and if there is a crimp. I'm not positive just a primer will push that bullet up the tube far enough that another cartridge will chamber. I've already mentioned we don't know how tight the op's bullets were in the neck of his reloads.

Now I've had "squib" loads in the far past, but even with earmuffs on you can hear something. I don't classify a squib load as just a primer, but one that doesn't have the full charge of powder.

[JonB_in_Glencoe]

I had to look up Nick Harvey, as I was not familiar with his load manuals. In any case, best practice is to always consult at least two sources. Since multiple sources apparently list more than 24 grains with a 55 gr bullet, getting a straight answer on just charge weight could be frustrating. Better to be frustrated than lose or gun or get hurt though...

Some day I might get around to writing up an analysis of load manuals, the various ways they get the data, how they format it for publishing, and most importantly, why data changes. To do the subject justice would probably take a few thousand words, manual excerpts excluded. Adding the sidebars about how powders combust, variables in components, differences in instrumentation and test platforms, and how data is presented would likely double the effort. And yes, there would also be a sidebar discussion of whether lawyers have dictated lower load levels or if we just better understand the details than in the 'good old days.'

Back to the topic at hand - assuming the firearm mechanism still functioned as designed after ~2k rounds in service, this was an over pressure event that grossly exceeded the yield point of the brass which at the moment of firing is little more than a gasket. As Larry et al have said, proper malfunction clearing procedures would have made the difference for a squib. Preventing a reload problem requires more attention at the reloading bench.

I'd be interested in your analysis of load manuals (when you do the write up). I only searched out and posted the Max loads from My two favorite manuals and Hodgdon, because 25.5gr stuck in my mind... as that's my pet load for a CZ-527 chambered for 223rem, of course I worked up from suggested start load.

I stumbled onto Nick Harvey (an Australian) reloading manual when I loaded my first Rifle rounds (280 rem) using Hawke's Bullets (they use a thicker soft copper jacket and pure lead core), they recommended the Nick Harvey Manual, He generates his own data. I really like it for comparison purposes and it has more European calibers than most American manuals. You can never have enough paper reloading manuals.

[vzerone]

None really taken Beeman.

I was thinking, those Berry bullets might be softer. I've never shot them, are they? What is the alloy inside the plated jacket? Maybe just a primer would throw a Berry bullet up the tube further then a conventional jacket/core swaged bullet. They certainly do a cast bullet. The furthest up the barrel bullets with just a primer I found were most always in a revolver.

If there was a bullet up the bore and another round fired behind it that would do what we have seen. The weak area on the AR bolt is at extractor. The reason for that is that actually that is were another bolt lug would be, but that can't be done because the extractor has to be there. So when the high pressure hits the bolt it actually tilts the bolt tilting it the most at the extractor. Now we're talking tilting in the thousandths of an inch, but with that kind of high pressure it doesn't take much to blow the case in that area near the extractor. I've not known anyone that blew an AR that gas came back along the carrier/bolt group and blew gas in their face because it really can't do that. In that sense I feel AR are more safe then bolt action rifles. I'd say when blow ups happen between the two types of actions that the bolt guns are less forgiving. AR's almost always dump the gas down the magazine well.

[popper]

The AR firing pin barely protrudes from the bolt face and it doesn't do so until the bolt is in full battery and fully rotated. Sorry, that is a myth. DPMS (pre-buy-out) factory 308 carbine. Shoulder just a hair too long. 40.5gr 4895 under a 165 cast. Safety ON and trigger NOT pulled. Nice chunk of concrete missing. Nothing through my shoulder, did take a long time before a naughty work came out. Gun is OK so I do the same experiment with just a case sized the same. Won't go into battery - i.e. no lug lockup. Brass is LC07 MG fired. I've learned to run it 2x in the sizer. I check for high primers. Don't depend on a dwg. or mfg. for 'fail-safe'. look at the pics. Bottom of carrier is GONE. Bolt has extra 'dent' in it.

[M-Tecs]

Sorry, that is a myth.

Easy enough to test with a primed case. Chamber the primed case and pull the charging handle back until the bolt rotates slightly and pull the trigger.

[vzerone]

popper your AR was out of spec. I'm not overly fond of the first series of DPMS. Haven't had a chance to inspect their Gen II. That's part of what I'm talking about in building AR's, knowing that ka ka, and what to do about it.

[M-Tecs]

Sorry, that is a myth. DPMS (pre-buy-out) factory 308 carbine. Shoulder just a hair too long. 40.5gr 4895 under a 165 cast. Safety ON and trigger NOT pulled. Nice chunk of concrete missing. Nothing through my shoulder, did take a long time before a naughty work came out. Gun is OK so I do the same experiment with just a case sized the same. Won't go into battery - i.e. no lug lockup. Brass is LC07 MG fired. I've learned to run it 2x in the sizer. I check for high primers. Don't depend on a dwg. or mfg. for 'fail-safe'. look at the pics. Bottom of carrier is GONE. Bolt has extra 'dent' in it.

What caused the gun to fire?

[popper]

Slam fire due to bad HS I assume. IIRC, I tossed that brass but saw no damage to it. I've gone through >500 rnds since then, no problem. Found case a LONG way from incident. Also had a total case head separation in 40SW. Recovered the case head, no burn marks on the brass. No damage to the gun which jammed next rnd on the case left in the chamber. It was a recalled lot of FC brass I must have picked up at the range. AR design is good but not fail-safe. My 300 BO bolts and the other DPMS will do the same thing - bolt starts to lock & fp WILL move. Out of spec? Unless each and every part is measured and verified, all are 'out-of-spec'. IIRC the OP said he was shooting 60gr, not 100.
I read the Book, it's Sunday morning - the preacher is boring so I'm off fishing.

[M-Tecs]

Popper

Did the primer show a firing pin indent?

My AR 10's have firing pin springs. Does the DPMS?

AR 10's are not standardized like AR 15's

[vzerone]

popper, first off NOTHING is fail-safe, especially when a human made and is operating it. Here's a little thread from a popular forum on firing pins and bolts. Notice CMMG participated in it and they are a major AR manufacturer. Also consider how many people make AR componants. For example the receivers...a CNC milling machine will make them. Could be done out of your garage. Anyways here's the link, read it: https://www.ar15.com/forums/ar-15/-/118-552200/?page=1 I repeat it's an interesting read and I personally don't hold AR15.COM has the absolute supreme intelligence, just as people feel about wikipedia.

Now I spoke with Berry Bullets on the phone this morning. Their lead alloy core in their 55 grain FMJ bullets, that the op used, are of a soft alloy. They would not state exact composition. So it's may be possible the primer and no powder case may have popped it into the bore far enough for another round to chamber. I think it was Beeman that was interested in what Berry had to say about the bullet, so here you are sir.

popper...specs and out of specs is one the differences between upperline AR's and the el cheapo's. Remember also that AR10's were never mil-speced, only the M16 and they claim AR15's since most of it's componants are compadible with M16's.

Finally...I agree with M-Tec's post on slamfire.

[vzerone]

BeeMan that all sounds very good, except for one thing still bothering me. That is how normal the primer looks. I've seen a few scenarios that look exactly like the op's, but one big difference....the primer was GONE! A very high percentage of these incident seem to blow the case at the extractor side. I mentioned previously about the bolt tilting that way because of the lack of a bolt lug on that side to make room for the extractor.

I believe the M197 chamber pressure high pressure test is about 70,000 psi. Little interesting chart:
M193 Chamber pressure...............52,000 psi
M196 Chamber pressure ..............52,000 psi (tracer)
M197 Chamber pressure...........70,000 psi (high pressure test)
M855 Chamber pressure ..............55,000 psi
M856 Chamber pressure ..............55,000 psi (tracer)
M995 Chamber pressure...............50,250 psi (armor piercing)

[Larry Gibson]

With a bullet stuck in the throat, leade, etc. an AR bolt/carrier when drawn to the rear and released has sufficient momentum to push the next feeding bullet back into the case. I saw this many times over the years even with M193 and M855 ammo. It is particularly noticeable in FTE (failure to extract) where the fired case stays in the chamber, the action functions and the bullet of the feeding round is stopped by the case in the chamber. That bullet invariably gets pushed back into the case. In those instances the round will not chamber of course.

However, in the OPs case the soft jacketed bullet stuck in the leade was probably push a bit further into the bore while the bullet in the feeding cartridge was shoved back into the case. That in essence created a "110 gr bullet" (the combined weight of the 2 bullets) over 24 gr H335......obviously not good!

BTW; 24 gr H335 under a 55 gr bullet is a medium range 223 Rem load. It takes 25 - 25.5 gr to make the SAAMI MAP. It takes 26.5 to 27 gr to equal the 5.56 MAP. My standard load since the mid '70s has been 26.5 gr H335 in LC cases with a WSR or CCI 450 primer under a 55 gr Hornady SX (12 and 14" twist barrels). The measured psi (Oehler M43) in a 223 Rem chamber runs right at 59,500 to 60,000 psi.

Note; the psi I give are transducer/gauge psi's. The previous post psi's are CUPs. I'll also add that M193 made since around 2003 or 4 has the same measured psi as M855; 60 to 62,000 + psi. The older M193 ran around 58,000 psi which is about 4,000 +/- psi more than most 223 Rem factory cartridges are loaded to.

[JBinMN]

First off... I am glad that the OP was not hurt, nor anyone around him during this "event".

Secondly, "Many Thanks!" to all of you knowledgeable folks who are participating in this discussion. I am learning quite a bit from it & although an "AR" is not in my possession at this time, but likely may be in the future... my days in the Corps, using an M16A1 & knowing its' components, has allowed me to follow the discussion so far. Even if one doesn't have any knowledge of the workings of the AR15, or the M16 platform, there is a good bit of knowledge to be learned from these posts in this topic, IMO. Particularly the bits about safety & focus in reloading & safe operations of firearms(particularly regarding FTF) that are applicable to this "event". Thanks again for your sharing!
:)

[vzerone]

I'm impressed that if it was essentially two bullets being fired that the bolt lugs didn't at least crack. I sure would like to know what the barrel looks like especially where the bullets were located before firing. Like I've mentioned I've seen a lot of AR blowups and a high percentage of the time the shooter walks away uninjured. How many shooters I've seen that had a blowup on a bolt action wood stock getting injured from wood splinters.

[vzerone]

Larry if you're talking about my psi's being cup, that is not what I find. Those come from the TM43-0001-27 Army manual and are on page 10-9 and listed as psi. Here's the pfd link to the manual: http://pdf.textfiles.com/manuals/MILITARY/united_states_army_tm_43-0001-27%20-%2029_april_1994.pdf

For those of you that haven't read this it's an interesting read.

[Larry Gibson]

Yes the pressures are listed as "psi" but they are measured via CUP method. All older published pressures taken via CUP and LUP were refered to as "psi". However, with the advent of modern and better pressure measuring methods (transducer and strain gauge) the older CUP and LUP measurements are refered to as; CUP or LUP. Transducer and strain gage measurements are now referred to as "psi". Some newer manuals such as Lyman's uses and denotes both types of measurement. Also SAAMI lists pressure specs for both types of measurement.

[Larry Gibson]

Previous TMs had definitions and testing procedures. Also the pressures listed are MAPs (Maximum Allowable Pressure). That is not necessarily what any lot of cartrdges is actually loaded to. Cartridges are loaded to a +/- velocity spec not to exceed the MAP.

[vzerone]

Larry I just merely posted what I did to give a generalization of what kind of pressures are dealt with in the 223/5.56, although we can't be certain what the op's pressures were. We would have to pressure test his ammon in pressure testing barrel because as you very well know it's you can't do it on a AR unless it was a special model just for pressure testing. You sure can't get a strain gauge over the chamber an AR. BTW the Army correlated those psi figures. There is an error factor in both systems, I believe CUP runs as high as 3000 psi error and piezo has much less error in the 1300's psi range. Both have to take into account what the cartridge case wall changes except in I believe CIP which a hole is drill eliminating having to deal with what the case wall would change.

We unfortunately have gone off track and I apologize. Larry I still would like to hear from you why the primer of his culprit case looks pretty normal if indeed two bullet were fired.

[Larry Gibson]

vzerone

Please don't misunderstand, I was not being critical at all. I was just explaining the why the psi (CUP) figures you posted were different than the psi I posted. It's like driving your car about 60 MPH, your also going about 100 KPH......same speed just a different method of measurement.

I measure psi via a strain gauge and a M43 Oehler PBL. It is on a very tight chambered (223 chamber) Contender Carbine barrel. BTW; it's not an "error factor" correction but in terminology we use today is an ES (Extreme Spread) or a =/- specification. The transducer/gauge psi measurement systems are considered more consistent and give a much better "picture" via a pressure trace. That is why most manufacturers use the newer system. NATO spec ammunition is also measured with a transducer mounted at the case mouth. They can then measure psi's on actual AR barrels. However, such measurements generally produce slightly lower psi's and somewhat different pressure traces.

"I still would like to hear from you why the primer of his culprit case looks pretty normal if indeed two bullet were fired."

I can't say that the primer "looks pretty normal" from that picture. It appears to be severely flattened with the primer pocket completely blown. I can't discern if part of the primer was also blow out where the case head was blown out. Note the severe case extrusion into the ejector hole; that only happens from extreme pressure. Given other severe damage such as the cracked bolt carrier and the swelled receiver are also indicative of extreme pressure.

Watch the video carefully paying attention to the sequence of events prior to the ka-boom.

Note the recoil of the rifle when fired during the previous target engagements.

Note, when the FTF occurs the non recoil of the rifle, just a click heard and no impact down range.

OP then clears the supposed FTF cartridge by pulling back on the op handle and letting go of the op handle so the bolt fed and chambered the next round on it's own.

OP then pulls trigger and the ka-boom then happens.

My conclusion; The supposed FTF was not a FTF; it did fire except there was no powder in that case. The force of the primer pushed the bullet into the leade where it stuck. When the OP extracted the supposed FTF cartridge he actually just extracted a fired case. When the OP let go of the op handle (pulled fully back) the recoil spring drove the next cartridge from the magazine into the chamber. The momentum of the bolt carrier/bolt drove that cartridge completely into the chamber and the bolt closed. On chambering the bullet of the chambering cartridge struck the rear of the stuck bullet and may or may not have pushed it further into the bore. The bullet in the cartridge was driven back into the case. At that point there was 110 gr of the combined weight of both bullets in front of 24 gr H335 in the cartridge, a gross over load. The OP pulled the trigger and the rest is as they say......history.

[vzerone]

Larry, oh no no no, there's no mis-understanding at all. We're on the same page there.

I blew up that case head photo. Look at it, that primer still has a round edge. I've seen much much flatter primers from excessive pressure then that. Kind of like you troweled cement in the primer pocket. I totaly agree with you on the extrusion of the case head into the ejector hole. My theory on the primer is that the case blew, also blowing out much of the primer pocket as you noted, thus releasing the high pressure from all of it being on the primer. I feel the carrier cracked mainly from the gas pressure blown into it from the blown case. The bolt took all the pressure and much of it off the carrier. Only pressure imparted to the carrier on an AR is 1. gas pressure from the gas tube and 2. some force from the bolt through the cam pin. Do we know if the bolt openned? If it didn't open then no force on the cam pin. I don't know how much pressure there was in the barrel at the gas port, thus don't know how much gas pressured entered the carrier cylinder area. Like I said I think the carrier busted from the eruption of the gas out of the blown case.

I'm very thankful of the Lord the op didn't get hurt and thank Lord again his eyes are okay. It's a shame to have learned a lesson the hard way.

Here's the pic:

204301

Even the primer indentation isn't flattened excessively, nor did the primer try to flow in the firing pin hole.

[Prospector Howard]

I do believe the talk about 24gr of H335 behind 110 grains of projectiles is a red herring. I don't care if the stuck in the bore item is 10gr or 55gr, once you fire the new bullet into anything that is lodged in a barrel as tight as that first 55gr projectile, you're going to have a blown up rifle.

[Larry Gibson]

That's why flatness of a fired primer is a poor indication of pressure. I tested some Winchester white box M193 a few years back for a friend. He said he was getting 3340 fps from his 20" AR. That is a bit fast.

I stopped after 7 rounds as rounds 5 and 6 hit 68,300 psi. Average for the 7 rounds was 65,700 psi. Velocity was 3351 fps out of the 21" test barrel. That is a bit warm. Point is by the look of the primers, expasion ring and case head expansion measurements there was no indication of that much psi.

I have pressure tested thousand of rounds over the last 8 years and seldom consider condition of a fired primer anymore.

[MaryB]

To many different primers and different hardness of them...

[higgins]

A Lee Factory Crimp Die will allow you to get a good crimp without the occasional case buckling seen when applying a firm roll crimp on a case that is a tad longer then the one used to adjust the die.

[cpaspr]

I do believe the talk about 24gr of H335 behind 110 grains of projectiles is a red herring. I don't care if the stuck in the bore item is 10gr or 55gr, once you fire the new bullet into anything that is lodged in a barrel as tight as that first 55gr projectile, you're going to have a blown up rifle.

PH - I don't think the second bullet fired into the bullet stuck in the bore. The bullet of the second round ran into the bullet stuck in the bore, pushing the second bullet back in the case. So now both bullets were nose to tail, ahead of the powder. One bullet was partially in the case, the other was tight against it's nose. So when the trigger was pulled, it really was the same as if there was a single 110gr bullet ahead of the powder.

[Larry Gibson]

Concur with cpaspr ^^^^^^

[PbHurler]

Nothing to add other than I'm glad you weren't hurt. You'll acquire a new rifle: harder to do with body parts.

[Prospector Howard]

PH - I don't think the second bullet fired into the bullet stuck in the bore. The bullet of the second round ran into the bullet stuck in the bore, pushing the second bullet back in the case. So now both bullets were nose to tail, ahead of the powder. One bullet was partially in the case, the other was tight against it's nose. So when the trigger was pulled, it really was the same as if there was a single 110gr bullet ahead of the powder.

I don't want to beat this into the ground, but I think most people underestimate the energy in a primer. I've never purposely or accidently fired a "primer only" squib in any firearm including a 55gr jacketed bullet in a .223/5.56, but I'd bet the bullet went into the barrell more than you're thinking in your theory. Either way you have a stuck bullet as Larry said and a bullet behind it that isn't stuck. That's really not the same as one 110gr bullet. I don't think the distance between them matters as much as you all do. Also, I don't think I want to ruin any rifles to test these theories to prove anything.

[popper]

OOB thought was incorrect - looking closely at the case head - what is left of it. Totally extruded into the bolt face. Bolt had to be locked up. I'd be surprised if it unlocked by gas pressure at all.
edit: yes the primer was dented. No there is no spring like an AK. You can test the 'interlock' of the bolt by rotating and pushing on the FP base. Mine move when bolt is ~1/2 way locked. Same as the AR15 (BO). Bolt rotates when it hits the case head but I don't think the hammer can fall until near lockup.

[M-Tecs]

The hammer will fall anytime the carrier is out of the way. The firing pin should not protrude from the bolt face until the bolt is rotated into battery.

To test with carrier out and the bolt all the way forward hold the firing pin all the way in and push the bolt in and not when the pin protrudes from the bolt face.

[adam_mac84]

Thanks for the great discussion guys (am the OP). I have since changed my reloading practices, and will never clear a malfunction without a second look at what is coming out (even on the clock). Saving a few cents per round in 223 cost me $700 in replacement firearm, so although I am very thankful to not have been injured, was a relatively $$ lesson to learn (but no cost compares to a permanent physical injury!!).

I still have a hard time on a primer only squib (wouldn't there have been a 'pop' or 'puff' sound?), but the evidence is hard to refute. My OAL shouldn't have put the bullet into the lands causing it to get 'grabbed' if it were just a dead strike. I have gone frame by frame in the video (100 fps). I did not catch a good image of the casing ejected, can only see it. If I really zoom in, I PERSONALLY believe I see a taper on the end of the case. Leaving bullet in the barrel. the 110grains did get pushed out, but not before destruction of the upper. I do think that bullet set back was a main part of this event. Either due to obstruction, or chambering process.

To me, I will assume and operate from this point as the entire thing was my fault (reloading practice faults and malfunction clearing faults). By fixing these I hope to reduce my chances of future failure/injury.

[Larry Gibson]

Excellent attitude.....learn from our own mistakes.......

Hold hard, shoot straight.....

[jonp]

With a bullet stuck in the throat, leade, etc. an AR bolt/carrier when drawn to the rear and released has sufficient momentum to push the next feeding bullet back into the case. I saw this many times over the years even with M193 and M855 ammo. It is particularly noticeable in FTE (failure to extract) where the fired case stays in the chamber, the action functions and the bullet of the feeding round is stopped by the case in the chamber. That bullet invariably gets pushed back into the case. In those instances the round will not chamber of course.

However, in the OPs case the soft jacketed bullet stuck in the leade was probably push a bit further into the bore while the bullet in the feeding cartridge was shoved back into the case. That in essence created a "110 gr bullet" (the combined weight of the 2 bullets) over 24 gr H335......obviously not good!

BTW; 24 gr H335 under a 55 gr bullet is a medium range 223 Rem load. It takes 25 - 25.5 gr to make the SAAMI MAP. It takes 26.5 to 27 gr to equal the 5.56 MAP. My standard load since the mid '70s has been 26.5 gr H335 in LC cases with a WSR or CCI 450 primer under a 55 gr Hornady SX (12 and 14" twist barrels). The measured psi (Oehler M43) in a 223 Rem chamber runs right at 59,500 to 60,000 psi.

Note; the psi I give are transducer/gauge psi's. The previous post psi's are CUPs. I'll also add that M193 made since around 2003 or 4 has the same measured psi as M855; 60 to 62,000 + psi. The older M193 ran around 58,000 psi which is about 4,000 +/- psi more than most 223 Rem factory cartridges are loaded to.

Insufficient crimp on the second or would it matter as the force of chambering would push the bullet back no matter what?