Dude, fucking stop! An AR firing pin CANNOT! touch the primer until the bolt is locked. How fucking stupid of a design it would be if it could.
- Thread starter Southernspeed
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You’re an idiot.
Naw man all's good with me. Thanks for the offer. This ain't nothin' compared the the Bear Pit. Maybe the OP would appreciate it though.
No skin off my nose, I don't have a dog in this fight! Folk just need to agree to disagree
This is absolutely fricken crazy! This just happened to me last night on a thermal coyote hunt, and until I started searching and found this thread, I had no clue what an OOB Discharge was.
Here is the scenario in short........ This is a 6 X 6.8 custom chamber AR 15.
I had a coyote coming in and it hung up. I squeezed the trigger and click. This makes sense as I realized I hadn’t racked a round since getting out of the truck. So, I rack one in (remember it’s pitch black darkness) without any oddities with the chambering. I squeeze the trigger and distinctly heard 2 rounds go off. The first was a normal suppressed sounding round but milliseconds later a very loud boom! My mag was destroyed. After inspecting, I found the first (normal) brass from the first round in my brass catcher and it looked normal. The blown up round was found on the ground.
I lost sleep wondering what I did wrong and how it could have physically happened in the first place.
Here is my theory: I chambered a normal round which went off normally. The bolt extracted that case and dumped it in my brass catcher, the bolt picked up a cockeyed round that was not in a normal position and somehow blew it up. The round that blew up is pinched and almost flattened……see pics
The barrlel/chamber looks fine, but the upper is smoked and the bolt is jammed hard in the carrier. So new reciever and BCG was done today. I'll test fire tomorrow....hopefully without flinching bad
I need to figure out what happened so I can try to do every thing to prevent it from ever happening again.
Here is the scenario in short........ This is a 6 X 6.8 custom chamber AR 15.
I had a coyote coming in and it hung up. I squeezed the trigger and click. This makes sense as I realized I hadn’t racked a round since getting out of the truck. So, I rack one in (remember it’s pitch black darkness) without any oddities with the chambering. I squeeze the trigger and distinctly heard 2 rounds go off. The first was a normal suppressed sounding round but milliseconds later a very loud boom! My mag was destroyed. After inspecting, I found the first (normal) brass from the first round in my brass catcher and it looked normal. The blown up round was found on the ground.
I lost sleep wondering what I did wrong and how it could have physically happened in the first place.
Here is my theory: I chambered a normal round which went off normally. The bolt extracted that case and dumped it in my brass catcher, the bolt picked up a cockeyed round that was not in a normal position and somehow blew it up. The round that blew up is pinched and almost flattened……see pics
The barrlel/chamber looks fine, but the upper is smoked and the bolt is jammed hard in the carrier. So new reciever and BCG was done today. I'll test fire tomorrow....hopefully without flinching bad
I need to figure out what happened so I can try to do every thing to prevent it from ever happening again.
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So it fired & ejected a 223, next round went boom.
Are you 100% certain a 300 BO round didn't accidentally get loaded in the mag.
Barrel clear???
Sorry I should have added (and will fix the post). This is a 6 X 6.8 custom chamber.
In that case are you 100% certain a regular 6.8 round didn't find it's way in your mag?
Only other thing I can think of would be if you used SSA brass & the neck just let go causing an over pressure.
Good questions, but the first round went off normal, and the second round blew up before getting to the chamber (I think) based on the flattening of the brass. But then again, the bullet had to have found it's way down the barrel or through the mag???
Also, it couldn't have been a regular 6.8 as the neck needed to be sized down for the bullet.
Yeah good point. A 300BO will chamber in 223 because it's so much shorter. 6.8 in a 6 x 6.8 not so much.
Pictures are pretty grainy, but it looks like the case was in the chamber by the way the back end is rolled open.
I'm leaning towards the neck letting go (cracking cicumferencialy) & trying to follow the bullet. This would result in a big pressure spike and some of that pressure would blow back down the outside of the case. That would be the only way I can figure the case carcass ejected. There was no rim.
How many reloads on the cases and what brand case were they?
The reason I suspected SSA brass in because they had known batches of bad brass. I had a whole box of factory loaded 6.8 SSA that split every single neck in multiple locations.
I'm not convinced the case carcass was ejected.....I feel that it just fell out when I was in the heat of the moment trying to figure out what just happened. I found it on the ground, not in the brass catcher.
have both Star Line and S & B brass. Most of it has been loaded 5 times or less....but no more than 5 times.
Here are a few more pics...
Maybe a common denominator is self-assembled AR's in Wild Cat calibers....who knows, but this event has really got me questioning the AR platform.
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Just let go of the out of battery idea. If the cam pin didn't shear it's not possible for the firing pin to reach the primer till the bolt is locked. The AR is actually a very sound design in that regard.
The odds are super duper slim, but not impossible that you had a weird cockeyed jam that somehow set it off. I would expect the blown case to look different than yours though if it was completely out of battery.
Something like a bolt over ride, but damn the odds are slim with a fatter bolt & case. Those bolt overs or should I say under are nasty. Luckily mine didn't go boom. 223 barely fit up there & I had a hell of a time getting it out.
The neck is completely missing on your case that went boom, IMO that's a pretty good clue.
Take a good look in your chamber to see if any of the missing neck is still in there.
Is your cam pin broken? If not it didn't fire out of battery. At least not via the firing pin.
Hell I seriously doubt doubt even a broken cam pin would enable OOB firing pin strike. The top half of the cam pin would need to be completely dislodged before I'd entertain it. The cam pins usually shear at the firing pin bore & cant come completely out due to close fit to upper. The firing pin in that case will not let the cam pin turn. It would bind the firing pin up, but the cam pin will be forced to follow the cam path.
I haven't ever broken an AR cam pin, but I did brake a Benelli Super Black Eagle cam pin. They function very similar to an AR. Bolt has to rotate locked before the pin will reach the primer. What I described above is exactly what happened. The broken cam pin remained in place & the bolt locked in battery. I got a click no bang thanks to the bound up firing pin. That was literally a lucky Duck!
The odds are super duper slim, but not impossible that you had a weird cockeyed jam that somehow set it off. I would expect the blown case to look different than yours though if it was completely out of battery.
Something like a bolt over ride, but damn the odds are slim with a fatter bolt & case. Those bolt overs or should I say under are nasty. Luckily mine didn't go boom. 223 barely fit up there & I had a hell of a time getting it out.
The neck is completely missing on your case that went boom, IMO that's a pretty good clue.
Take a good look in your chamber to see if any of the missing neck is still in there.
Is your cam pin broken? If not it didn't fire out of battery. At least not via the firing pin.
Hell I seriously doubt doubt even a broken cam pin would enable OOB firing pin strike. The top half of the cam pin would need to be completely dislodged before I'd entertain it. The cam pins usually shear at the firing pin bore & cant come completely out due to close fit to upper. The firing pin in that case will not let the cam pin turn. It would bind the firing pin up, but the cam pin will be forced to follow the cam path.
I haven't ever broken an AR cam pin, but I did brake a Benelli Super Black Eagle cam pin. They function very similar to an AR. Bolt has to rotate locked before the pin will reach the primer. What I described above is exactly what happened. The broken cam pin remained in place & the bolt locked in battery. I got a click no bang thanks to the bound up firing pin. That was literally a lucky Duck!
Thanks a ton 357
The cam pin is intact and jammed hard. I couldn't get it to budge...I just trashed the whole thing. Also, I failed to mention that when I got home and dropped the lower, my firing pin fell right out the back of the carrier. Not sure if that's a clue as well. The cotter pin was sheared, but that probably happened with the explosion...maybe not and was already broken and a big part of the failure. ??
The chamber looks really good a clean. Thinking about it more, the bullet had to have made it down the barrel. The upper has a gouge in the top but I think that was from all the brass and other shrapnel not the bullet.
The cam pin is intact and jammed hard. I couldn't get it to budge...I just trashed the whole thing. Also, I failed to mention that when I got home and dropped the lower, my firing pin fell right out the back of the carrier. Not sure if that's a clue as well. The cotter pin was sheared, but that probably happened with the explosion...maybe not and was already broken and a big part of the failure. ??
The chamber looks really good a clean. Thinking about it more, the bullet had to have made it down the barrel. The upper has a gouge in the top but I think that was from all the brass and other shrapnel not the bullet.
The broken cotter pin most likely sheared in the explosion as you said. It doesn't affect forward movement of the pin, just keeps it from flying out the back into the buffer tube.
Was the case head stuck in the bolt? Any damage to the bolt lugs or extracter?
Without being able to put eyes on it my best guess is still that the brass separated at the neck to shoulder junction. The results fit that theory better than anything else I can think of.
So, what I am reading is that one round went off as normal, and the second detonated upon loading. Sounds like a slam fire.
@MuleyTime I’d say the most likely cause is a primer that was not set below flush during the priming step. This is the most likely cause for a slam fire, and one of the VERY few causes of an actual OOB in an AR15.
@MuleyTime I’d say the most likely cause is a primer that was not set below flush during the priming step. This is the most likely cause for a slam fire, and one of the VERY few causes of an actual OOB in an AR15.
The first round was a squib with only a primer to propel the bullet far enough into the barrel to chamber another round. CLICK!!! YOU rack one in, which EJECTS the spent squib case into brass catcher. Squib bullet comes out suppressor, 2nd goes kaboom. Did that bullet exit barrel too?
Your rifle was exploding by the time the first bullet came out. I'm betting you only thought you didn't have a loaded chamber when it went click.
With the damage to the carrier like that I'm leaning toward a barrel obstruction.
And it wouldn't necessarily have to be a second round to do it either. If the bullet didn't make it past the gas port and the bolt didn't unlock then all that gas is now trapped.
But I'd also suspect in that case for the lugs to be sheared. It almost looks like the bolt couldn't unlock, lugs held and the pressure escaped through the firing pin hole? But that's a lot of pressure.
To have the carrier ripped open like that with intact lugs is a bit of a head scratcher really.
I've seen some beat to shit M4s and some amazing damage and still keep going in a firefight, bent barrels, broken lugs, etc., so whatever happened was certainly out of the norm, that's a fact.
And it wouldn't necessarily have to be a second round to do it either. If the bullet didn't make it past the gas port and the bolt didn't unlock then all that gas is now trapped.
But I'd also suspect in that case for the lugs to be sheared. It almost looks like the bolt couldn't unlock, lugs held and the pressure escaped through the firing pin hole? But that's a lot of pressure.
To have the carrier ripped open like that with intact lugs is a bit of a head scratcher really.
I've seen some beat to shit M4s and some amazing damage and still keep going in a firefight, bent barrels, broken lugs, etc., so whatever happened was certainly out of the norm, that's a fact.
No. The click was legit.
Upon lots of further investigation, I'm now leaning towards the slam fire due to primer not being seated fully theory as mentioned above.
Looks like that AA9 from your 10mm loading made it into the case. Especially since you said it was the first round. That would for sure cause this...
I know you said your cycled the thrower. Did you take the hopper off and turn it upside down and dump it after??? Some stays in my auto throw after cycling thr thrower to empty that's why I always take the hopper off and turn the dumper upside down and get that last amount out. That amount of AA9 mixed in with your first charge could definitely be the cause here...
I know you said your cycled the thrower. Did you take the hopper off and turn it upside down and dump it after??? Some stays in my auto throw after cycling thr thrower to empty that's why I always take the hopper off and turn the dumper upside down and get that last amount out. That amount of AA9 mixed in with your first charge could definitely be the cause here...
For what it's worth, I just entered your listed load data into GRT( with the exception of the projectile which was swapped for a 220 grn Sierra HPRN) & the pressure came out at 23KPSI & change for the 10grn of H110 but, 144KPsi at 18.8 grn which was the highest extrapolation calculated.
From the damage you've shown, I would imagine you've double charged & are a blessed man indeed.
Thanks for the info. Yep, definitely a double charge. I’ve seen a few guys on YouTube who have had exactly the same result from double charge remanufactured ammo. Fortunately for them the ammo companies fully reimbursed them and the gun companies gave them new rifles.
Live and learn eh!
question about over pressure:
i read something about a “flash over” that was basically a half charged powder load that could cause over pressure.
so that the powder level was below the primer hole and too much ignited at once
is that a real thing? or just internet bs?
It is a real thing to varying degrees. I’ve experienced wildly varying velocities when trying to develop lightweight sub loads. Holding the rifle muzzle up then lowering gently to firing position ( so primer was covered) gave expected velocities but just chambering a round as normal would create some very high velocities and flattened primers (300 aac) , I would imagine this varies with powder type but never looked too deep into it.
Thanks for that. I use H110 almost exclusively for my 300BLK loads; with Accurate 1680 substituted for subs when I can find it. I typically use 9.5-10 gr. for subs depending on the bullet, and 19-20 gr for supers, again, depending on the bullet I’m loading.
Will try that powder if I can find it locally.
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I bought some SOCOM , looks identical to H110. I’d have to check my notes but I think I used 10.4 for avg 1050fps but I had function issues. BUT I had just rebuilt this rifle and although it ran 100 rounds of S&B subs just fine, I’m wondering if I didn’t get the gas block aligned correctly. I’ll check on that and go from there.
@357Max I tried out the SOCOM and had issues with it. Have you used it for subs in a gas gun? I tried 11, 10.5 and 10 grains. 11 were super mostly and would cycle the gun sometimes but sometimes it wouldn't pick up a new round and didn't hold the bolt back. 10.5 would eject rounds but would close the bolt on an empty chamber everytime. These were Berry's 220 projectiles.
I'd just put 90 S&B subs through it and it ran fine. I'm guessing SOCOM just isn't 'gassy' enough for 300aac subs?
I checked my gas block, it all lines up fine. Your thoughts?
I'd just put 90 S&B subs through it and it ran fine. I'm guessing SOCOM just isn't 'gassy' enough for 300aac subs?
I checked my gas block, it all lines up fine. Your thoughts?
I haven't run any Subs with it. Works great for Supers & it should work very well with subs but you obviously need more gas.
FWIW - I run an adjustable gas block on mine. With a fixed block you might not get enough gas with the SoCom as you said.
Guessing it's burning cleaner as well.
I’ll try it on supers. I may need to open up the gas hole in the barrel a touch then run an adjustable gb. The hole seems very small but all my barrels are the same.
Idiot/newbie question, what is an “out of battery” explosion?
The round detonating before locked in the chamber by the bolt.
The only idiot questions are the ones not asked
This is from one, it is almost impossible for an AR-15 to fire out of battery because it has to be in battery for the bolt to lock and the bolt must lock to allow the firing pin to strike the cartridge.
With simple blow back guns, like this 9mm came from, the firing pin can strike the cartridge even if the bolt is not closed all the way. This one blew the magazine out the bottom of a Olympic Arms 9mm upper on an AR-15, but no damage to gun or shooter (me) otherwise. Pistol caliber ARs are usually simple blow back and not locking.
I did a lot of back and forth with H110 and CFE Blk for supers/subs and CFE, while being dirtier, was better in terms of accuracy with subs. It also seems to produce more gas and cycles more reliably. I also use VV120 which is far cleaner but the optimal gas tuning is in a narrower range where CFE has a wider range where it just works. I use H110 for supers and really haven't found anything better.
Once you know what it is, how it happens, and the danger of it happening it’s than neat to see all the engineering that goes into a gun to prevent it.
Something that cannot happen in an AR with parts that are in spec.
