Busting the myth of the bulge.

[DuaneWessels]

This article focuses on 9mmP Bulge Busting.

This bulge busting story is going to drive me crazy.
There's more myths than facts out there. Most reloaders do not need to Bulge Bust.

This bulge at the bottom of the case is usually caused by high pressure loads or loose chambers. Some handguns have a looser chamber to assist in the feeding of ammo.

Sport Shooters with fancy 9mmP Open Guns running major ammo will usually find their cases have bulged after firing due to the higher pressures they are running.

Glocks do not automatically cause bulges.
A modern Glock's chamber has no more an unsupported chamber than any other modern handgun.
Old Glock 22's had a problem but newer models have fixed the issue.

There are 2 methods to fix this.
A Roll Sizer, which is an expensive bit of kit.
Or one of the Lee Precision Bulge Buster kits.

The Lee method of fixing a bulge is to use either of their Bulge Buster Kits with a Factory Crimp Die.

You do this by removing the crimp sleeve from the Factory Crimp Die and forcing the case all the way through the Factory Crimp Die. The case needs to go all the way through the Die body so that the bulge at the bottom of the case can be forced out with the carbide ring inside the Factory Crimp Die.

Lee does not list a Bulge Buster for 9mmP but reloaders have figured out to use the 9mm Makarov Factory Crimp Die.

Why use a 9mm Makarov Factory Crimp Die?
The base of the 9mmP case and a 9mm Makarov case is almost the same.
9mm Makarov has a base of .3915inch, 9mmP has a base of .3910inch...this tiny difference is what allows you to use the 9mm Makarov Factory Crimp Die to bulge 9mmP cases.


 

But 9mm Makarov is not in any other way the same as 9mmP and the important difference are:
9mm Makarov is shorter by 1.05mm.
9mm Makarov has a case mouth of 0.3902inch.
9mmP has a case mouth of 0.3800inch.

9mmP is a tapered case, the bottom is bigger than the top.
9mm Makarov is a straight walled case, the bottom and the top is basically the same size. Again this is one of the reasons why you use this Factory Crimp Die to bulge bust 9mmP.
And the tapered case of the 9mmP is why you cannot use a 9mmP Factory Crimp Die to bulge bust.

And no you cannot use a 9mm Makarov Factory Crimp Die to crimp 9mmP.
It will not give a sufficient or correct TAPER crimp because of the difference in case design.

And yes 9mmP is to be TAPER crimped not ROLL crimped. Your ideal crimp should prevent any type of bullet setback and your case mouth should measure 0.3800 inch after you have applied your crimp.

So your ammo is not feeding correctly in your handgun. The slide does not close all the way...you might have a bulged case problem.

Now before you run off to buy a Bulge Buster check this first.

Is your sizing die correctly installed and are you completing the stroke? Size a case and barrel drop or case gauge it. If it drops or gauges correctly, your case is not the issue and you do not have a bulge problem. (To barrel drop, remove the barrel from your gun)

Now check if your Cartridge Overall Length is not the problem...which with the new coated bullets on the market these days, is usually the problem.

Load a dummy round, no powder or primer. Drop it in your barrel.
Did it plunk in? Does it sit flush? Can it spin freely in the chamber?

If not you need to lower your Cartridge Overall Length slowly until the rounds fits in your chamber. Coated bullets can have a bigger ogive (the shape of the bullet) and you need to load them shorter than a CMJ.

If this is the case, you need to lower your COL. Do this bit by bit until the round fits but take note not to compress the powder charge!

Did you flare your case sufficiently to allow the bullet to seat? If you do not add enough flare you could buckle the case while seating the bullet. This will also cause feeding issues.

Now if you have eliminated the above you have a bulged case.

Again, there are 2 ways to address this issue.
Roll Sizing which is probably the best way but is a very expensive solution or the Lee Precision Bulge Buster.

Lee Precision has 2 models, one for use on a Single Stage Press or a model for their excellent APP Press. The APP option is by far the quickest way to Bulge Bust.

I hope this read will bust the myth of the bulge.

[Treeman]

I really enjoy your write ups, learn or confirm something every time.
Thank you for the efforts.

[oafpatroll]

I really enjoy your write ups, learn or confirm something every time.
Thank you for the efforts.

Hear hear! Low BS, high value stuff.

I have only ever come across one bulged 9mm case in 25+ years of reloading for the calibre and oddly enough it was last weekend. A round failed to feed into my CZ75 and locked the slide slightly OOB. Wrestled it open and found that there was a bulge near the base of the case. 

[Treeman]

Was that the first bulge you had or the first you recognized? I only ask because this subject makes me think of cases that would not work which after a few minutes of head scratching I just dumped.

[oafpatroll]

Was that the first bulge you had or the first you recognized? I only ask because this subject makes me think of cases that would not work which after a few minutes of head scratching I just dumped.

Fair question. I thought about the very one while I was at the loading bench today. It seems unlikely that in a couple of decades of brass scrounging I never came across one before so I think it must be the latter rather than the former.

What got me thinking about it was the unusually high number of split mouth 9mm cases I threw out today. Out of 1203 cases I found and discarded 7 that had split or cracked mouths. This is significant as I decap on a single then wet tumble and then prime by hand. Only then do I put them together on the ancient Pro 1000. That's a lot of opportunities to spot a glaringly obvious defect. A bulge is easy to miss till it's so bad that it won't chamber and if your chambers are on the generous side there's even less chance of noticing.