What caused this? input please.

[jeepyj]

Today I was at the range and every thing went very well except I had something odd happen with my 9mm. I was shooting 4.1 grains of green dot over a 356242 / 120 grain cast boolit out of my glock. (I'm aware of the polygonal barrel vs cast) but have shot a boat load this same boolit through this pistol but recently switched to green dot because of powder availability. I only had one, nothing seemed different. I just happen to notice because the brass flew up straight and landed on my sleeve. In total I shot 50 rounds and this is the only one that Did this. Any thoughts?
There is a small dent in the cartridge where it looks like it hit while feeding. It really appears it wasn't fully seated when it went off but I was shooting one round at a time at some steel but hopefully someone will be able to shed some light on this. Also the primer seemed to be fully seated.
jeepyj

137993137994137995

[DLCTEX]

Looks like Glock bulge case fatigue to me.

[willie_pete]

I can't tell from the pic; is the firing pin rectangle imprint in line with the blowout?

wp

[MtGun44]

Too much pressure. Excess powder or boolit pushed into case during feeding.
Everyone wants to think the gun "fired unlocked" but with essentially all designs,
this is impossible. There is an unsupported portion of the case at the feed ramp
and when the pressure is excessive, it blows out.

Extremely high probability of user error, inadequate neck tension/taper crimp letting
boolit push in during feeding, too much powder (often a double charge) are the normal
causes. Most people spend a great deal of time looking for unicorn footprints
and other reasons it wasn't their fault. . . . . sorry, but the odds are very high that
the guy in the mirror made a reloading mistake. Finding out exactly what it was and
making sure not to do it again is the solution.

[country gent]

How many firing has the case in question been thru? How many in a glock? The larger chamber unsupported area takes its toll. Several reasons for this unsupported tired brass. bulges being worked re worked ( even though the bulge buster remove the bulge so brass chambers the stress is there from the bulges). Over pressure is also a possibility if this was the case you were on raged edge as thios will also blow magazine out of firearm and or a display of gas and brass particles. I dont al;ways go along with flat out over pressure but it is one of the more common reasons.

[David2011]

The blowout appears to be just to the left of inline with the firing pin mark in the third image when its blown up- uh, --enlarged.

Was this range brass, possibly from a range where USPSA matches are shot? I've know several guys that wouldn't pick up their own brass to reuse after loading it to 9mm Major. They're running a 147 grain jacketed bullet in the 1450-1550 fps range out of 9mm brass so its pre-weakened before you get it. Add to that any of the previously posted variables and the brass is the weakest link in the chain. If you're the only person to have ever used this brass at least you know its history.

David

[jeepyj]

Too much pressure. Excess powder or boolit pushed into case during feeding.
Everyone wants to think the gun "fired unlocked" but with essentially all designs,
this is impossible. There is an unsupported portion of the case at the feed ramp
and when the pressure is excessive, it blows out.

Extremely high probability of user error, inadequate neck tension/taper crimp letting
boolit push in during feeding, too much powder (often a double charge) are the normal
causes. Most people spend a great deal of time looking for unicorn footprints
and other reasons it wasn't their fault. . . . . sorry, but the odds are very high that
the guy in the mirror made a reloading mistake. Finding out exactly what it was and
making sure not to do it again is the solution.

Mtgun44 first off thank you, I wasn't looking for any type sugar coating. Everything was clear in my mind and I went back through everything and you are correct. While I thought I was under by .3 grains I was over by .1 grain. The Lyman manual lists that load as 4.4 grains maximum without a doubt I was at 4.5 grains. Even though I don't generally push maximum loads this time something I must have ether misread or ???
I am confident that there was no double charge as this one would easly overflow the case but without a doubt it was a strong charge.
Even though I made a mistake I'm glad I brought it foward to find out the real truth. It will be a another lesson that I know I'll learn from and hopefully others as well.
Thank you,
jeepyj

[jeepyj]

[QUOTE=David2011;3230961]The blowout appears to be just to the left of inline with the firing pin mark in the third image when its blown up- uh, --enlarged.

Was this range brass, possibly from a range where USPSA matches are shot? I've know several guys that wouldn't pick up their own brass to reuse after loading it to 9mm Major. They're running a 147 grain jacketed bullet in the 1450-1550 fps range out of 9mm brass so its pre-weakened before you get it. Add to that any of the previously posted variables and the brass is the weakest link in the chain. If you're the only person to have ever used this brass at least you know its history.

David[/QUOTE
Dave2011,
Honestly I don't know the history its brass that I've purchased along the line. As I mentioned in my post to Mtgun44 the load was a bit over according to the latest Lyman manual. Apparently enough to make it not happy that's for sure. I'll cut the load back to 4.1 grains where I originally intended and give that a try. We'll see
jeepyj

[Plate plinker]

Mtgun44 is right on. Even at .1 over you should not have a blowout unless the brass was prestressed. Check your neck tension (crimp).
Glad you backed off a bit.

for those not in the know you can usually spot "major 9" brass because it's blown out or at very least has a funny line near the base indicating higher pressure. I generally don't pickup 9mm brass at the matches unless for scrap.

[Echo]

I vote for weakened brass - I have seen identical occurrences with factory .45ACP wadcutters. Weak brass, for whatever reason.

[Certaindeaf]

Pre-Glocked brass. That's a low load.. unless it set back, as others have said.

[wv109323]

Take the barrel out of your pistol. Put the piece of brass in the chamber. You will most likely find the rupture lines up with the unsupported part of the chamber. If you can bisect the brass you may find more info.

[10x]

Take the barrel out of your pistol. Put the piece of brass in the chamber. You will most likely find the rupture lines up with the unsupported part of the chamber. If you can bisect the brass you may find more info.

This ^^^^^

[dakotashooter2]

Too much pressure. Excess powder or boolit pushed into case during feeding.
Everyone wants to think the gun "fired unlocked" but with essentially all designs,
this is impossible. There is an unsupported portion of the case at the feed ramp
and when the pressure is excessive, it blows out.

Extremely high probability of user error, inadequate neck tension/taper crimp letting
boolit push in during feeding, too much powder (often a double charge) are the normal
causes. Most people spend a great deal of time looking for unicorn footprints
and other reasons it wasn't their fault. . . . . sorry, but the odds are very high that
the guy in the mirror made a reloading mistake. Finding out exactly what it was and
making sure not to do it again is the solution.

I agree that this is something most people overlook. Especially if loading mixed brass. Even when sorted I have found considerable differences in tension in brass of the same headstamp. Giving them the "push test" after loaded never hurts.

[MtGun44]

9mm is a problem child in reloading. Brass is far, far more variable than most
cartridges and pushin by a loose boolit makes a HUGE difference in pressure
due to tiny internal volume. This can happen due to case thickness
irregularities with different brands of brass letting the dimensions and then
neck tension and/or crimp get out of spec.

No intent to be harsh on anyone, but this is a serious hobby and we need to
be quite firm and serious with ourselves on how to be safe. When a case blows,
the pressure was more a than the case could hold. We need to understand what
caused that.

I have a .38 Super, was loaded to max pressures because of the need to meet Major Caliber
specs for IPSC competition. With any brass brand except Winchester, the load was
fine and I could load the brass literally many dozens of times. With Win brass, even
with +P, there was an ugly bulge in the feed ramp area (unsupported area) or it would
blow out.

I worked diligently to make sure no Win brass got picked up accidentally, and didn't
lower my loads due to the need for competition. Now that I don't use it for competition,
I have backed my loads down a good bit and don't sweat the brass headstamp like
I did before.

May need to look at headstamps or other brass issues with 9mm and see if there
is a link. But in the end, the answer is still "too much pressure".

It is good the gun is OK. Plastic framed guns are often totaled by this event.