9mm case head blowout

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Yet another reason to case gauge rounds. 9 major brass that has been heavily stressed (either because it is monstrously over pressure, or because it has been overloaded a few times) usually gets expanded at the base - where regular sizing dies cannot reach. That brass will then not pass a case gauge, even though it will easy pass a "plunk test," particularly in a barrel with generous clearances around the base like the OP's.

I continue to maintain that the punk test is for setting up COAL, and case gauging is a more exacting a reliable QC check on finished rounds.
Whish is why I scrap 9MM brass that fails my Wilson case gauge after sizing, and I agree, the plunk test is for OAL, although it works if the ammo is only ever fired in that one gun.
 
Another vote for fired out of battery. Pretty obvious where the blow out happened and now it won't fully chamber.

That looks wrong. The case may be too long. Headspaced correctly the rim abatement should be about flush with chamber wall.

It is fully chambered. Flush with the back of the barrel hood is fully chambered on a 1911.
 
I believe OP explained that that is fully chambered.

How does he actually know that when the picture he posted has the case not in full battery? Unsupported is one thing, and I see the same bulge around his blow out in some of the range brass that I buy, I pitch them as soon as I see them, and his barrel design doesn't rule out anything.
There is no way that case backed out of his barrel with a hole in it and a bulge larger than the chamber size.

That is physically impossible. It fired before it was the whole way into the chamber and blew out.
Why is the big question.
I wouldn't be looking at a brass problem as far as PMC is concerned, I would be looking at how this gun fired this round when it obviously didn't make it into full battery.
I don't care what kind of feed ramp or unsupported barrel you have. We all shoot them every day with no problems.

Sorry but I can't see a brass problem here from the pictures the OP posted. I see a mechanical failure of some kind that may have been caused by and expanded case head from, possibly, an over pressured round, it didn't fire in the chamber and blow out the side of the case larger than the bore of the chamber, and then come back out.
 
Measure length of the blown brass. Also check your other fired rounds for any sign of expansion ring in case web. Could be the gun needs repair if others have same issue.

* as a stupid question, if factory 9mm is seating the same with 10 to 15 thousands unsupported, are we sure the barrel isnt cut for 9x18?
 
The barrel ramp looks like it has the guppy cut which reduces support over a std ramp barrel. These barrels have always had minimal support. I suspect the case was weakened prior to loading or your having bullet setback problems.
 
View attachment 894859

Should be like this. I believe the max "slop" is only 3 or 5 thousandths.

There is no headspace issue, I fit the barrel myself. I have never gotten an exansion ring and I've shot thousands of rounds from this gun. I wasn't asking for help, I just thought it was interesting and that I would post a picture.

7766DAC3-75CE-499E-862A-9B032DB6823B.jpg
 
The barrel ramp looks like it has the guppy cut which reduces support over a std ramp barrel. .

In the 3rd pic of the OPS original post, it shows the blowout in the same location as the guppy cut. Can't really see the cut very well in that pic, but the OP's pic in post 37 helps!
 
Just to refresh my memory I just ran the depth rod on my dial indicator down a Win 9mm case, the web ends .050 above the extractor groove. I would be scared to shoot that.
 
I am suprised other brass fired in that barrel isn't bulged or ringed. I have never seen a factory barrel with that little support. Here's a reference pic from web.

that level of non-support is typical of traditional 1911’s. Colt Delta’s used to have that kind of unsupported brass in 10mm... which wasn’t good.
 
Just checked 2 1911s, a high power, and a star superbee at home. Granted the 1911s are newer 45s, but none of these look like that. I would say the widest ramp area is maybe a little over 1/4 of the case rim. That pic looks like more than half of the chamber is chamfered.

Regardless it's his pistol. If it works and he's happy, that's fine by me.
 
range brass

Range brass is the problem.
OR bullet set back on chambering. Range brass does not provide the same neck tension/bullet pull on all.
The LEE Undersize Sizing Die will provided more neck tension when used with a smaller expander.


With pressures running at 35,000 to 38,500 PSI , your lucky gun was an all steel model. Plastic guns may not hold the pressure as well.

New Starline brass is $76.50 for 500 pcs. Or buy 2000 @ $13.5 cents each.

https://www.thehighroad.org/index.php?media/albums/kaboom.24/
 
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Range brass is the problem.
OR bullet set back on chambering. Range brass does not provide the same neck tension/bullet pull on all.
The LEE Undersize Sizing Die will provided more neck tension when used with a smaller expander.


With pressures running at 35,000 to 38,500 PSI , your lucky gun was an all steel model. Plastic guns may not hold the pressure as well.

New Starline brass is $76.50 for 500 pcs. Or buy 2000 @ $13.5 cents each.

https://www.thehighroad.org/index.php?media/albums/kaboom.24/

Yay, brass for the cost of loaded ammo!
 
Had that happen twice with a Smith 39-2. One was, I think, from a bullet telescoping into the case....thin brass didn't have enough tension. Other time was with some brass that had a weird groove in the face of the head of the case on the inside. Broke one grip and damaged the magazine. Not fully supported either. Destroyed all that brass and have stuck to modern, commercial American since and after thousands of rounds, no problems. It is an eye opener.
 
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