What caused this bulge in the 9mm Luger shell case?

martyd

martyd

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9mm Luger Case

I refer to this as a pregnant shell case.

There is a bulge at the base of the case which is quite noticeable.

I appears to me that the case is not chambered all the way when firing.
Which could happen with a full automatic firearm.
OR
There is a defect in the barrel chamber.

I see this fairly often on range brass.

Sorry I couldn't get a good pic from the side.

Any idea what causes this?
 

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The crease looks like the cases are hitting the edge of the ejection port of the slide as they are thrown after firing. I see what looks like a bulge below them, and the only thing I can think of that creates that sort of bulge at the base of the case is an unsupported chamber, where the feed ramp undercuts a small portion of the chamber, to ease feeding. Glocks are known for that, and several others as well.

Both can be sized out of the case, but the bulge will shorten case life.
 
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Probably fired from a Glock. If the firing pin indent is rectangular, then it’s pretty certain.
 
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Another cause is when fired from full auto /open bolt weapons the ignition gets a little early as the weapon heats up and get the chamber a little dirty, causing what is commonly called "Glocked Brass!"

Is it safe to reload? Both Yes and No! Yes if it is the first or second time, No if you have no idea how many times this happened! (This only applies to Glock type and open bolt guns.) After getting repeatedly bulged the brass will separate in front of the rim, leaving the case wall in the chamber, Time to buy or make a stuck case remover!

I had a full auto MAC-10 9mm for over 20 years and fired over 85,000 rounds of reloads in it, and never had a stuck case. My ex-B-I-L has a Glock 17 and has had several!

My practice was to gather up the bugled cased, resize and tumble, and give to someone I didn't like or just recycle them.
 
Years ago my agency issued reloaded ammo for practice. One day I was firing some of it in my Beretta 92FS Type M and it locked up tight. After forcing the slide back the ejected round I noticed it was bulged out at the base (and had been fired in a 9mm SMG in the past). This must have resized it a bit because that same round fired and ejected perfectly in my issued 92F.
 
I thank all of you for responding to my question!

The firing pin mark on the primer is a standard round mark.

Thanks,
Marty
 
Any deep "Ding" in a case is not a good thing.

Standard wear and tear is ok but when you start tossing in xtra case wear
or flat spots to the rim from ejections, it will "Kill" the life of the case, big time.

With the right load and fit, you should get 7-10 target reloads, if you can find the cases........ (pistols)
Full loads are a different animal.
 
martyd said:
I thank all of you for responding to my question!

The firing pin mark on the primer is a standard round mark.

Thanks,
Marty
Click to expand...

In that case there's a good chance it was fired in someone's ubercool race gun at 9mm Major power. The chamber could have been over beveled/relieved for feeding, resulting in too little case support.
 
9mm Luger shells take a beating ... going from clip , they are dragged across frame , hit a feed ramp some bounce up and off the top of the chamber while the slide slams them home rather roughly ...
Then after firing they get ripped from the chanber by a extractor , slam into the ejector at high velocity and usually get dinged by the slide / barrel assembly..the case is trying to get out and the slide is slamming shut ...after bouncing off one or more gun parts they hit anything in it's path and then hit the conc floor ... denting the mouth ...
I amazed 9mm Luger shells aren't beat slap to death after 6 reloadings .

Your case looks like most of the cases I pick up ...they get beat up because they lead a hard life .
Those little dings won't hurt a thing and there is no defect with the gun . Load them untill you loose them or the mouth cracks ... I usually loose the em first !
Gary
 
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I acquire a lot of 9mm brass from SIGs and Glocks (Fed agent quals) and none has that mark on them. Yet someone always blames it on a Glock.
 
Was it fired from a war time Browning HP? I've seen bulged lower case from Browning HPs, the war time pistols, Canadian built, often dented cases like that.
Geoff
Who was young and curious.
 
SMSgt said:
I acquire a lot of 9mm brass from SIGs and Glocks (Fed agent quals) and none has that mark on them. Yet someone always blames it on a Glock.
Click to expand...
The famous Glock smile of Gen 2. Gen 3 onward have a more completely supported chamber, no more smiles.
 
Hard to ascertain the exact contours but what people are calling a dent is the break between support and no support of the bulge. It continues into a less-pronounced arc bending toward the extractor groove that were caused by the flare to the feed-ramp. Do the exam and you'll find the extractor and ejector scars are consistently aligned relative to the bulge.

I have a 10mm that leaves its' ejection port calling card on hot-hot brass, but higher up on the case wall toward the mouth.
 
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Not knowing the firearm used to fire the rounds, I can't say what cause the crease, but the bulge is definitely from a firearm that does not have a fully supported chamber. The bulge can be fixed with a lee bulge buster kit with a lee factory carbide crimp die. I don't worry about 9MM cases too much, I load them as many times as I can and usually lose some of them at one range session and then find some leftover brass from someone else the next time I go to the range. With the two examples you show above, I would process them and see how bad the crease is after processing, usually the crease works out to just a slight nick after sizing and I would reload them.
 
I'll address the bulge not the crease. As mentioned above unsupported chambers of whatever brand and or full auto guns (law enforcement) tend to bulge the cases. Most of the time you can't even see this easily. However when you gauge check your finished rounds you find them grrr. I buy and load range brass for my competitions, load a lot too. 9mm and especially .40 are very prone to this. I tried the undersized dies and that helped a little. But when you load 500 rounds or so at a time and you have 15-25 rounds that won't gauge pass, that's a lot to break down with the plastic hammer from hell and it does get old quick! Not to mention lost primers as the brass is unusable. And it sucks when in the middle of a competition and your guns jams on a bulge case that you missed and your desperately trying to clear it while the clock ticks away lol.

So I bit the bullet and bought a rollsizer, a nice one too. All my brass gets rollsized first now and then loaded with the normal process. ALL my bulge issues are now gone! This may not be an option for the casual shooter $$ but for me it was a blessing.

Below is a pic of a .40 that does not play well and my rollsizer video.

https://drive.google.com/file/d/1dZVcXWXshn4usnj1z4l58su0phNP7hTx/view?usp=sharing
 

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Mike0251, I never heard of or saw a rollsizer before, THANKS for the video, now I know what it is!!!

I agree as a plinker and target shooter, I don't think I could justify the cost to purchase a device like that. I do use L.E. Wilson case gauges to check reloaded ammo and any that I missed and fail the gauge because of the bulge, I move to the side and use them in a revolver. Having a S&W 940, 25 and 610 save me the grief of separating my reloaded ammo.
 
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