Had a kaboom with my reloads.

[markm]

When it comes to overlength brass on bottle neck cartridges, I defer to the Hornady Handbook of Cartridge Reloading, Fourth Edition, Vol. 1, page 11. Hornady cautions against reloading overlength brass, due to overpressure concerns. On a service rifle with a generous cut on the leade, or worn throat, it is less likely to happen, but still possible.

I makes sense that it would be problematic, although I've never seen it happen.

I think I know where I errored. I must have loaded 5.56 cases using 223 load data.

The brass is the same. Some .223 brass will give a velocity boost, but not enough to kaboom on you.

[tomme boy]

You had a case head failure. That's it. It happens. What is shown is the unsupported case head that let go.

[Humpy70]

Several things come to mind here.

Using a depth mic measure from the back of the barrel extension to the back of the barrel on this and other factory barrels. This would not be the first time a barrel was chambered to where the headspace is correct but as pointed out the back of the case is unsupported.

Such will also happen if you pick up a case that has been in a fire and the head is soft.

Or it could have gone through the loading line annealing upside down.

If the barrel had water in it you will get similar.

I used to do M16A1 catastrophic failure investigations when I worked for the Army Small Cal Lab and worst I ever saw bowed the upper receiver out to where it was 2" with and the lower receiver the same way. The mag was inserted into the shooter's forearm.

I would like to see a pic of the back of the case and close up of the primer.

Was this a small rifle primer or was it a milspec primer you loaded?

You can also get a unlocked bolt ignition from a overheated weapon where the gas tube gets flexible due to heat, moves out of alignment and stops the bolt closing on a partially chambered round and if barrel temp is about 400 deg F it will likely cook off in about 8 to 10 seconds and can be particularly nasty.

I estimate the pressure on this case was about 90,000 lbs which can occur from several factors.

A section of cleaning rod left in the barrel will to it as well.

[opngrnd]

Is a delayed cook off possible? I've had two in 9mm before, both with factory Winchester White Box. I was lucky to just get sprayed with mostly unburned powder.

[Humpy70]

Not sure what your definition of "delayed cook off entails"

We did cook off tests on M16s which consist of 500 single shots in 500 seconds and start a stop watch when the 501st round is chambered and it takes 8 to 10 seconds for them to cook off.

The rule of thumb in testing in machineguns is if you get a stoppage you have 5 SECONDs to open the bolt which means you don't sit there and scratch your head and ask Bubba to ask Jethro what they think and get a consensus of what to do. If bolt is not opened the temp rises and if if bolt it locked and goes off no problem.

If you are right in the middle of opening the bolt giving the barrel time to heat the round you are asking for a problem.

We had a gunner and a loader killed in Alaska who opened the bolt on a failure to fire and we got word it happened and they were both unconscious in ICU. The Chief of the Small Cal Lab asked if the local commander wanted on site accident investigation as he was ready to put three of us on a plane and the plan was one guy would sit between their beds 24 hours a day hoping one would wake up and the first question to be asked was did you open a bolt on a misfire?

As it turned out the local commander talked to his local attorney who advised him not to ask for investigation as it was going to look bad on his career so he declined. A couple days later one died and the Commander got nervous and asked for investigation and he was told he had obstructed an investigation and thus he had the ball so to speak. Several days later the other one died.

Bottom line was OPEN within 5 seconds and if you don't then don't touch it for 30 minutes. This is drilled into professional gunners and there are signs on the ranges telling all that and yet we still had a gunner open a bolt about 10 seconds into a stoppage and he got brass fragments in his face/hand/arm.

I worked with a guy who was a M60 gunner in Nam and they had human waves hit them and he had hooked a sea bag full of belts together together and Charlies were in the wire and they sat down on final defense matrix and the barrel went white hot and when they stopped the gun kept firing about one round every few seconds and his Sergeant just reached up and broke the belt and let it shoot them out.

I relayed that story to the M60 engineer in charge and he said that must have been a very good barrel as they generally blow out the side of the barrel a on the way out the muzzle when it gets thinner before they go to white hot or the bolt lugs dig into the barrel socket and won't open at all.

We had armor suits designed for such testing with every inch of the gunner is protected and the object is to run it till it blows and the M16 tends to partially chamber as the bolt does not close.

It is easy to tell if you have a cook off as there will be no striker indent on the primer and the center of the primer reverse blows into striker opening on bolt face and you will likely find a piece of the primer inside the bolt.

Much the same thing can happen on a M16 with insufficient striker energy which means the striker does not have enough energy to hold the primer indent forward long enough for the pressure to back down and it craters around the edge. This is one of the reasons the MILSPEC primer cups are heavier which also means you have to whack hell out of the primer to get it to fire.

In the gov't small arms the hardest primer to fire is Cal 50 BMG, the second hardest is the primer for 5.56 and it goes down to where the easiest primer to fire is on 38 Special Wad Cutter ammo.

I bought a Rem 7615 about ten years back and it was reverse flowing described above with MILSPEC ammo as I have the equipment to conduct striker energy testing to see if it is in spec so I called Wolff Springs and ordered a new hammer spring and checked the spring energy and it was in spec and the same ammo stopped reverse flowing immediately.

If you load standard small rifle primers in 5.56 ammo you will likely get a punched primer as the cups are too thin to hold up to the higher pressures. You read tons of opinions about the pressure will blow the guns up but nobody has every proved the THEORY. I had a buddy at Winchester and he said they had plenty of blanked primers but nobody ever reported a blown commercial rifle as is the warning you always read.

When the black rifles got into competition there were lots of pierced primers and I wrote a number of posts explaining it and when folks put the right primers in the problem went away.

So a cook off is not necessarily a bad thing, stupidity is.

For instance we got rifles in where guys downloaded blank propellant from several rounds and put it in one case and shot it and even though there was no bullet the case let go.

When we got a rifle in for investigation and there was no case included and the rifle checked out dimensionally and metallurgically that only leads to our thinking WHY DIDN'T THEY INCLUDE THE CASE?

I never saw a catastrophic failure on a M16 barrel with a round coming out the side of the barrel but I can tell you we had a M14 cook off test and on the 14th mag of continuous full auto at round 276 a round exited the barrel about half way to the gas port.

I had a buddy in SF in a fight in Nam catch a M1 Garand stock on fire but barrel held.

When I left the gov't we had never had a case of a action failure on anything from the 1903 Springfield onward.

Just remembered saw a pile of 98 Mausers that were all fired with cleaning rods in barrel and not one action had lug shear.

A guy tried to sue the government saying the Springfield was a bad design. He converted one to 308 Norma Magnum, loaded the rounds with a 30% overload, heated the front of the action with a torch so he could mount scope mount, heated the rear ring same way to mount a scope and then decided he wanted a Griffin & Howe mount and heated the whole side of the receiver so he could drill it. Then he mounted the scope.

My buddy was the gov't expert witness and the lawyer for the plaintiff asked his name, occupation etc and then he screwed up. He asked him to outline the development of the 1903 and my buddy asked if he wanted a brief overview or in depth survey and lawyer said a brief overview was fine and my buddy quit talking and had 456 pages of typed pages of testimony. Lawyer had no more questions. Jury was out 15 minutes and was back and ruled the would be gunsmith was stupid above and beyond the call of ignorance and that ended his lawsuit.

My buddy said the bolt came out the back of the rifle and caved his face in and really looked bad. My buddy and taken a 03 and chambered it and loaded it with same load the guy used and ran a thousand rounds through it and the action held fine. Moral to this story is just because you have a acetylene torch doesn't mean you know what you are going.

Also aware of handloaders who put primer in and missed putting powder in and launched a bullet about an inch or so down bore and put a loaded one behind it. Now that will mess things ups.

Oh by the way when barrels fail they tend to fail at 9:00 or 3:00 for some reasons. Very few have seen a 6 to 12 oclock failure and I have not and never talked to a guy that did.

CIP a guy at Trinidad Gunsmith school class in about 1950 and they were told by PO ACKLEY to never re-chamber a gov't barrel for a magnum round and one of the students chambered a 1917 Enfield in 300 Win Mag and barrel failed shearing off four fingers on his left hand. As a side not P14 barrels and known to start splitting at the muzzle and work their way back towards the action. They are also know to have been improperly forged on the third shift at Eddystone.

That is only known because another buddy knew the 3rd shift plant manager at Eddystone who continually caught guys not forging correctly or at the right temperature. My buddy rented a room from him 35 years later and he passed that tidbit to him and he passed it to me as he was the one that trained me at the Army Small Cal Lab. The guy that trained me was a treasure trove of info and had a memory that would impress any computer designer.

[scottcc]

Several things come to mind here.

Using a depth mic measure from the back of the barrel extension to the back of the barrel on this and other factory barrels. This would not be the first time a barrel was chambered to where the headspace is correct but as pointed out the back of the case is unsupported.

Such will also happen if you pick up a case that has been in a fire and the head is soft.

Or it could have gone through the loading line annealing upside down.

If the barrel had water in it you will get similar.

I used to do M16A1 catastrophic failure investigations when I worked for the Army Small Cal Lab and worst I ever saw bowed the upper receiver out to where it was 2" with and the lower receiver the same way. The mag was inserted into the shooter's forearm.

I would like to see a pic of the back of the case and close up of the primer.

Was this a small rifle primer or was it a milspec primer you loaded?

You can also get a unlocked bolt ignition from a overheated weapon where the gas tube gets flexible due to heat, moves out of alignment and stops the bolt closing on a partially chambered round and if barrel temp is about 400 deg F it will likely cook off in about 8 to 10 seconds and can be particularly nasty.

I estimate the pressure on this case was about 90,000 lbs which can occur from several factors.

A section of cleaning rod left in the barrel will to it as well.

90,000 PSI would have likely destroyed the lower receiver, ? Not much damage to the lower maybe .5mm bowed on the right side of the magwell. I already tried another upper on it and it works fine. I only shot 1, 20 round mag before the failure. All of them reloads from the same batch. No sign of overpressure, until about halfway thru the 2nd mag, which had the round that blew out. There was no difference in sound or recoil that I could notice. Just a burn line on my pinky close to the magwell, and the gun stopped working.

I threw the whole batch out afterwards. According to Hornady's newest manual and Alliant's data, 23gr of ARComp should have been well below the max load. The primer is very flat and the case head lettering is flattened too.

Sent from my cp3705AS using Tapatalk

[Humpy70]

At about 110,000 the case will start to get liquid, Plastic deformation gets going around 70,000. I was at the Ruger plant and they had 55 gal drums of 70,000 lb proof cartridges that had been fired and they all showed plastic deformation but not to the degree those pics show. Now a case getting heated too hot(like a fire) will do it even with normal loads. There are some ranges folks throw brass into cans with trash and the trash gets lit, cases go soft, somebody retrieves the cases and tumbles them in stainless steel media there is no way to tell unless the hardness of the case was checked.

The primer backing out of the case looks suspicious which tells me the back of the barrel wasn't where it was supposed to be? Another outfit made target rifles and a barrel maker friend tipped me off that there was too much unsupported case head even though it was headspaced to gage and a number of those rifles had web failures.
That lead to the manufacturer buys several hundred thousand cases with extremely thick heads so the high pressure area was supported. Then again you could have had a case with a thin head that exposed the high pressure area to air instead of supported by steel.

I have also heard of folks getting a bigger caliber bullet in a box of smaller caliber bullets and pressures go out the roof which can go in some chambers as there is lots of room in military spec chambers.

The Sierra rep told me about such happening there about 30 years ago and then they started numbering the bullet boxes with lot number and employees could be identified that packed that lot.

I was at a match in NY state once and this guy was shooting M80 ball ammo in a M1A and all of a sudden a tracer goes down range, then another. The guys ammo was checked and there were no red tips in the ammo and then he had another tracer which meant someone at ammo plant had taken a handful of tracer bullets out of production before the tips were painted red and dumped them in a ball bullet hopper and they got loaded. I told the ammo engineers at Picatinny what happened and they said the tracer line was no where near the ball line and somebody was getting cute was the only thing they could figure as all his empties had the same head data on them.

In the pics the top row center pic shows the primer had backed out about .015 or so thus my conclusion the back of the barrel wasn't where it was supposed to be.

Guy at gun plants are not shooters and to them it is a job, not a passion like it is to us. CIP I was walking around Colt plant and this one guy was making a part and I recognized what he was making and I asked him what it did in a AR and he had no clue. The guy that trained me told me that he had seen similar at Rock Island Arsenal as folks get jobs there to keep money coming in during the winter and their main passion is farming. That is why there are gages made up for everything to bubba proof the final product.

Rock Island got a load of M14 barrels in and they were running first article acceptance and three out of a hundred barrels Rockwelled too soft. An analysis was run and they turned out not to be 4140 but cold rolled steel. The investigation revealed a couple guys in plant wanted barrels for their M1A so they switched out round stock on the rack with cold rolled blanks thinking no one would know the difference.

Then I saw M1911A1 slide come in that was certified to have been proof fired and was so stamped but it never had the firing pin channel drilled so how was it fired? It wasn't but it got stamped and certified as having done so.

[markm]

Is a delayed cook off possible? I've had two in 9mm before, both with factory Winchester White Box. I was lucky to just get sprayed with mostly unburned powder.

I've read of this with people trying to get sub sonic loads with reduced loads on standard powders. (I forget what it's called, but I've never seen any solid evidence of it being a real thing)

Simple delayed ignition won't cause it. I used to get that problem with WOLF primers and certain ball powders. It was the weirdest feeling when the ignition lagged a split second. Never cause pressure issues though.

[Humpy70]

yes such is possible if you load BELOW THE PUBLISHED MINIMUM IN THE LOADING MANUALS. Won't happen every round but is far more likely to give you a pressure spike.

[scottcc]

yes such is possible if you load BELOW THE PUBLISHED MINIMUM IN THE LOADING MANUALS. Won't happen every round but is far more likely to give you a pressure spike.

Hmm? It does seem possible the bolt was cycling before peek pressure, according to Hornady I was inside of the perimeters.