I loaded 250 rounds of 55 grain Sierra FMJ spire point, with 23.5 grains of H335. OAL 2.200. Case length 1.760. I had a rifle blow up. Then I took apart some rounds and they were all within spec. Went to the range. Another rifle blew up. I took apart all 250 rounds and they were from 23.4-25 grains, all within published specs. All the cases were from 1.755 to 1.765. All the OAL's were close to 2.200, some shorter, some longer, but none off by more than a couple of thousandths. All within published specs. Went to a reloading expert who took apart and measured everything and could not come up with an answer. We even tested the powder. Some were military brass. All were lightly crimped. I would like to know of anyone who has had a similar experience, and who actually discovered what happened? Not interested in more bleating about 'double charges' it wasn't, or 'you did something wrong, it's all your fault' that doesn't help. What would help would be actual answers and actual personal experiences. Thanks.
AR blowup
- Thread starter writerman
- Start date
paperpuncher
Gold $$ Contributor
What do you mean when you say we tested the powder? How did you test it? Is the powder commercially packaged H335 or milsurp pulldown. Did you check the bullet dia with a mic? Bad brass? Unsupported case head in the chamber? Maybe an issue with the rifles not the ammo?
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jelenko
Gold $$ Contributor
Have you measured your chamber? If the barrels from the two blown up rifles are still around.
The reason I ask is if the chamber were right at 1.760, the cases that are 1.765 would be crimped by the throat and cause higher pressure.
Brownells sells a really cheap chamber measure.
If you have a borescope you can insert a case into the chamber and insert the borescope from the muzzle.
The reason I ask is if the chamber were right at 1.760, the cases that are 1.765 would be crimped by the throat and cause higher pressure.
Brownells sells a really cheap chamber measure.
If you have a borescope you can insert a case into the chamber and insert the borescope from the muzzle.
ballisticdaddy
Gold $$ Contributor
Some photos of the "blown up" rifles might be helpful in trying to diagnose what the problem was.
mmcu
Gold $$ Contributor
Throwing, or weighing every charge? I'm going to assume throwing, as that's quite a range of charge weights if your target was 23.5 grains.
Case length greater than 1.760" could be the problem.
Mixed brass: Internal volumes can vary quite a bit. What headstamp of brass blew up in the rifles?
Pictures would be very helpful.
Case length greater than 1.760" could be the problem.
Mixed brass: Internal volumes can vary quite a bit. What headstamp of brass blew up in the rifles?
Pictures would be very helpful.
Like he said ... what do you mean by "blown up"?
Need to know the continuum of what you mean by "blow up". It could mean ... "It blew up my groups to over 2-MOA" ... or "My chamber blew up and it destroyed my rifle and sent shrapnel into my face". Would love to know where on that continuum your description applies.
dellet
Gold $$ Contributor
All things considered, I would send the powder back to the manufacture. Or the garbage can.
Unless there is more or better information.
Out Of Battery Detonation AR
I had an out of battery detonation, brought the destroyed .223 AR to one of the best gunsmiths in town, and he just shook his head and said he thought it might have been 'something about the round the gun didn't like.' I reloaded 100 rounds, same everything, no variation in that box at all. 50...
forum.accurateshooter.com
Unless there is more or better information.
Are you sure that the powder has not been contaminated by someone accidentally putting a fast burning powder in it?
If I had a situation where my gun blew up, and everything measured correctly, the first thing I would blame is the powder.
If I had a situation where my gun blew up, and everything measured correctly, the first thing I would blame is the powder.
joshb
Gold $$ Contributor
Uh……my Hornady book shows MAX at 23.2.
Good catch. Correction- Hodgdon shows 25.3 max for the 55 SPR SP
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Like everyone says pictures are needed.
The Sierra manual shows a start load of 23.6 and max load of 25.7gr H335 for 55gr projectiles. And, this is the AR load data, which differs from their bolt gun data (which is hotter than AR loads). Can't offer any additonal insight to the OP's problem, unfortunately...
Mike
Mike
Were they factory rifles or were they put together by an individual?
You asked for personal experiences. The only firearm I personally witnessed "blow up", meaning the firearm damaged, was a 1911 45 ACP. This was due to a barrel obstruction, a round fire into the pistol that had a bullet lodged in the barrel.
Firearms are supposedly proof tested before leaving the factory with ammo well over SAMMI pressure specs. So, something caused a tremendous pressure surge.
The 4the Edition of the Sierra Reloading Manual shows a load range of 22.9 to 25.9 for H335 for their 55 gain bullets in the 223 rem. However, this is for bolt rifles.
Military cases are known to be thicker thus requiring some reduction in powder charge.
I have personally experienced pressure surges with ball powder (namely H335 and H380) in extreme field temperatures of 90+ degrees, ammo exposed to direct sunlight in the field. These surges exhibited themselves in hard bolt lift, extractor engraving on the rim of the case, and extreme flattening of primers. In all cases the powder charges where below published maximum for that bullet. However, the rifle did not "blow up".
What where the environmental conditions and how many rounds of sustained fired were there when the firearm "blew up"?
Most of the catastrophic failures that I have read about were due to either incorrect powder mistakenly used, a double charge (pistols), incorrect ammo, or a barrel obstruction.
Trying to find the answer on the internet especially without a picture is a shot in the dark at best. If it was me, I would take the damaged firearm to an experienced gunsmith, along with ammo plus all information you have on the firearm and have it inspected by a professional.
Firearms are supposedly proof tested before leaving the factory with ammo well over SAMMI pressure specs. So, something caused a tremendous pressure surge.
The 4the Edition of the Sierra Reloading Manual shows a load range of 22.9 to 25.9 for H335 for their 55 gain bullets in the 223 rem. However, this is for bolt rifles.
Military cases are known to be thicker thus requiring some reduction in powder charge.
I have personally experienced pressure surges with ball powder (namely H335 and H380) in extreme field temperatures of 90+ degrees, ammo exposed to direct sunlight in the field. These surges exhibited themselves in hard bolt lift, extractor engraving on the rim of the case, and extreme flattening of primers. In all cases the powder charges where below published maximum for that bullet. However, the rifle did not "blow up".
What where the environmental conditions and how many rounds of sustained fired were there when the firearm "blew up"?
Most of the catastrophic failures that I have read about were due to either incorrect powder mistakenly used, a double charge (pistols), incorrect ammo, or a barrel obstruction.
Trying to find the answer on the internet especially without a picture is a shot in the dark at best. If it was me, I would take the damaged firearm to an experienced gunsmith, along with ammo plus all information you have on the firearm and have it inspected by a professional.
I wonder if something besides the firing pin struck the primer.I had an out of chamber boom in a 708 AR10 . what it looked like when it was taken out and what a brass should look like. gutted the mag
An AR-15 firing pin cannot reach the primer until the bolt fully cams into the locked position, and I am pretty sure it is the same on an AR-10.
dellet
Gold $$ Contributor
The bold print is conflicting.
Just like in the last thread where the gun blew up, your load is suspect. The last one blew up with less powder, loaded to a longer length. So this load was hotter than the last. And again the charge weight was over max in some data, and a starting load in others.
One more piece of information is trim length. 1.765” is over max length. At that length, a cartridge with 0 headspace could have as little as .007” clearance from the end of the neck to the the transition taper in the chamber to bullet diameter. There the case neck will pinch the bullet and cause a pressure spike.
New brass, or brass sized with the die touching the shell holder for maximum headspace, will most likely give you brass that is at or below minimum spec. About .010” shorter than max length.
What that will allow is for the case to move forward in the chamber .010”, where you have .007” clearance. Effectively headspacing off the rim of the neck. Then the neck stretches when fired creating a tighter crimp.
Overcharging and crimping the bullet in the chamber due to Long brass is a pretty likely answer.
6.5 forever
Silver $$ Contributor
High primer
Dirty pin, previous blown primer.
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