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Sporadic 9mm bulge


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Hello, and thanks in advance for your time.

I'm reloading 9mm Luger on an older 550B, although the dies are brand new. I'm an experienced loader although new to 9mm.

My issue is bulging at the case base. It doesn't happen consistently, but I would say 1 every 75 rounds. I'm loading 124gr jacketed with around 8.0grains of HS-6 and CCI small rifle primers. It's a pretty hot load, but I'm shooting 9mm Major through an STI Matchmaster.

The bulges are barely visible but they are causing the gun to not go into battery, leaving the slide about 1/8 of an inch away from locking up. The jam is then very difficult to free as the cartridge is really wedged in the barrel.

My OAL on the cartridge is in line with published data, and like I said, 98% of cartridges are fine and no issues with feeding. I've played around with the crimp and it seems to be well adjusted, same comment as previous, 98% of rounds are perfect.

It just seems bizarre that it's only happening about once every 75 rounds. I'm chamber checking everything, which I do for match rounds anyway but I'm shooting 800-1000 a week so that's a pain!

Again, thanks and fingers crossed you can help me!

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bulge near the bottom of the case.

you are doing major power factor.


you have a sentence that gives me pause;

"I'm chamber checking everything,"

this is how you are finding the bulge?

It may be that your fix is to get a die that does the entire case

I think it is called a U die or a Lee FCD.

as you are doing major PF you may want to inspect

your brass for a bright ring near the base

before you load it.


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Sounds like this is either "glocked" brass or used in other 9Major guns and the base/web are starting to expand. A U-die may help but if it's from repeated use in a 9Major, I would throw it away. Are you primer pockets still tight?

When you say you are chamber checking them, what are you using? A chamber gauge or the barrel? That makes a big difference, let us know...

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Not familiar with "glocked brass" what does a Glock do to brass?

I'm using the barrel to check. Yesterday a round that I thought I had barrel checked failed and I got a bad jam, I'm chocking that one up to the fact that my reloader is in the garage, cold night when I loaded and barrel checked. I'm thinking perhaps it expanded when it warmed up the next day.

All signs point to brass, I'll track what bulged cartridges headstamp is and follow up.

I'm just switching over to a Dillon 650XL today, so I'll see if the problem persists.

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With the 9mm round being a tapered round, you have to be sure you are sizing all the way down. Dies must contact shell plate & cam over some. Might not completely solve problem but might help.

I wouldn't have them contact the shellplate, that may break them. Ask me how I know :)

You should be able to fit a sheet of paper between the die and shellplate and pull it out without tearing it.

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I run all my pistol and rifle dies 1/4 - 1/2 turn past (tighter) contact with the shellplate...haven't broken anything yet...


It probably happen eventually. I'll take a pic of mine and post it when I get home. Also, the procedure I use now was what was recommended by Dillon when I called about my broken Dillon die.

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I have been reloading 9mm for many years and the only time I ever have the bulge problem is from brass scrounged at the range or bought in "mixed headstamp" lots. Making sure that your brass is going all the way into the sizer die is the answer. I also recommend resizing all your brass and checking them for correct length in a case gague often.

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A CasePro would be the ultimate solution.

I'm with Steve on this one. I have one and glad I do.

Not familiar with "glocked brass" what does a Glock do to brass?

Glock chambers are un-supported at the base of the case, which causes a bulge in this area depending on the load fired. See pic


Not true any more. This is my G35 barrel and it's 6 years old.


You will have better luck using the barrel from your gun to check them instead of a case gauge - they are not all exactly the same, case gauges - and you do plan to shoot them from your gun, not a case gauge.

With Steve again.

Also, make sure that you no A-Merc junk in the pile. Many threads on the reasons why, on many forums, plus from my own experience.

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