Author Topic: What causes case bulge?  (Read 1157 times)

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Offline redbaron

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What causes case bulge?
« on: May 21, 2019, 10:44:10 AM »
I've been plugging away on my new Dillon 550 for a few months now, loading all the pistol calibers I have and some 300 blackout and I absolutely love the machine.

I took out my new Canik TP9SFX yesterday and I ran into some issues that I have never had before when I loaded on my old Lee Classic Cast Turret. Out of about 300 rounds I had loaded up, maybe 5 had bulges so bad that only around half the cartridge would chamber in the pistol. A few had some minor bulging that caused the round to sit a little proud of the barrel when I did the plunk test. So maybe 12 total rounds out of 300 had some bulging issues that affected function to some degree, but the vast majority were fine.

What's the typical cause for this kind of case bulging? And why does it only happen to a handful of rounds? More importantly....how do I fix it?

Offline Tenbones

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Re: What causes case bulge?
« Reply #1 on: May 21, 2019, 11:31:09 AM »
Lots of questions need to be answered first because there could be several causes for this.  You mentioned that you were using the new Canik when you discovered the bulges.  Did you try to chamber these rounds in any of your other guns?  Do you think the bulges were caused by trying to chamber the rounds in the Canik or were the cases already bulged?  Do you clean, resize and lube your cases prior to reloading?  Are these cases ones you have reloaded before or are they cases you may have picked up at the range? How many times have you reloaded these cases as some may be becoming weak.  Your new Canik may have tighter tolerances and you may have to adjust your resizer.

You'll probably need to reload some more rounds and check each step in your reloading process to determine just where, or why, these bulges are happening.  It's little challenges like this that make reloading fun. ;)

Offline redbaron

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Re: What causes case bulge?
« Reply #2 on: May 21, 2019, 12:08:56 PM »
Thanks for the reply, I'll try to answer all those questions as best I can...

When I started noticing the stoppages, I pulled the Canik apart and plunked all the rounds I had with the Canik barrel. The ones that wouldn't plunk to my satisfaction I tried in the barrel of my SP-01, and I only had one that was fine in the SP-01 that didn't want to plunk in the Canik. The rest didn't plunk in either barrel

I don't think the bulge came from not chambering. After the first failure I started checking the rounds I hadn't fired yet and that's when I found the rest, so they hadn't even been loaded in the magazine and still had the bulge.

All cases were cleaned and sized prior to leading, and all of them I've shot in other pistols before. Even when I get range pickups, I typically take them home and clean and size them before I put them away just so I don't have to wonder about them. I don't really know how many times I've reloaded them, so maybe they are getting weak

Offline M1A4ME

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Re: What causes case bulge?
« Reply #3 on: May 21, 2019, 12:15:49 PM »
Are the bulges down around the base of the case? 

Are they all the way around or just a "bump" in one area at the base?

Or, are they nearly, or all the way, around the case about where the base of the bullet would be inside the case?

A bulge at the bottom may be due to not being fired in a pistol with a fully supported chamber and your new dies not completely resizing that out of the case.

A bulge part of the way down the case that is a fairly small area may be the bullet cocking a little bit sideways when being seated (I see this more on short .40 bullets than on 9MM, but it happens at times if the bullet isn't being seated straight for reasons due to bullet seater shape (different nosed bullets sometimes need a bullet seating stem just for them).

A bulge part of the way down that goes all the way around the case, or almost all the way around may be to the way you are setting up your crimp die.  Too much crimp can result in a bulge like that.  The die can't squeeze the case mouth in so it shoves the case wall down resulting in a bulge where there is a gap between the die and the case.

Good luck with it.  And, pictures of the offending cartridges help diagnose problems faster/easier.
Better to have it and not need it, than to need it and not have it.  So, if you see me walking the dogs with my SIG 556R, its okay.

Offline redbaron

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Re: What causes case bulge?
« Reply #4 on: May 21, 2019, 12:19:51 PM »
I'll get some pics together when I get home. The bulge is about half way down and all the way around. Issues with the crimp make some logical sense. I'm using a new set of Dillon dies for 9mm, and I was struggling a little with getting the crimp set correctly. It's entirely possible I over did it

Offline Tenbones

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Re: What causes case bulge?
« Reply #5 on: May 21, 2019, 12:46:44 PM »
That was going to be my next question, if you were still useing your old dies or got a set of Dillons with your new press, because the results of your 'plunk' test pretty much indicates that the problem is somewhere in your reloading process.  New dies could account for the problems you are having and they just need some adjustment.  M1A4ME brings up some good points to check and I think all it will take is a little more time at the reloader to iron out the kinks.  :)

Offline redbaron

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Re: What causes case bulge?
« Reply #6 on: May 21, 2019, 01:12:34 PM »
I had been shooting for a crimp of .376". That seemed to work ok with my .358 sized cast bullets. I'll have to go back and measure the bulging cases and see if I over did the crimp

Offline Wobbly

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Re: What causes case bulge?
« Reply #7 on: May 21, 2019, 02:09:11 PM »
Still not enough information supplied.

Mr Baron -
? You need to go back and read this thread on Max OAL:
https://czfirearms.us/index.php?topic=103620.0

- The chamber testing needs to be done using the "tightest chamber", either the Canik or CZ. Sounds as if you're unsure which is the more restrictive gun. That's OK, you'll simply need to "push" both guns. This needs to be done first because excessive OAL will mimic a case condition. And since it's impossible to see into the tapered chamber of a 9mm, we have to rule out everything.

- Especially read the part on page 2, if you're loading 147gr bullets. Those create case bulges in the middle of the case, not related to the dies or press.


? Then, just to be sure, also read this thread on Taper Crimp:
https://czfirearms.us/index.php?topic=78873.0
- Improper TC will create case bulges at the case mouth.


? Lastly measure the head of the brass you're using and compare that to the dimensions in your loading manual. The brass dimensions shown are Maximum Dimensions, meaning if you are 0.001" over it won't chamber. Range pickup fired in Major PF guns will create case bulges the case head so badly that it will no longer chamber. That's why Major PF shooters don't pick up their brass.

Hope this helps.


PS. We have a template for asking questions like this in the Stickies. We require a template because we need to know about 50 details you haven't begun to answer. Without this information these threads tend to drag on for 5 or 6, or 10, pages. All the while, you're not getting your answer, and we get frustrated wading though all the "helpful guessing" that tags along.

You deserve and answer. We'd like to give it to you today:)
« Last Edit: May 21, 2019, 02:27:31 PM by Wobbly »
In God we trust; On 'Starting Load' we rely.

Immature reloaders ask: What's wrong with this gun?
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Offline jwc007

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Re: What causes case bulge?
« Reply #8 on: May 21, 2019, 04:17:42 PM »
While you may have too tight of a crimp, there is a difference in Dillon Dies worth noting.

Dillon Dies are funneled a bit at the mouth to enhance case feeding, and do not always size the base of the case well.  I use Lee Dies on my Dillon 650, particularly the sizing/depriming Die.
Also, avoid Aguila Brass, as the base on their brass does not resize well.

BTW, my original Canik TP9V1 loves my reloads.  Also, it is my current CCW.


Canik TP9V1 accuracy at 50 feet with 124 grain Berry's FP Match reload
« Last Edit: May 21, 2019, 04:30:15 PM by jwc007 »
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For all of those killed by a 9mm: "Get up! You are not dead! You were shot with a useless cartridge!"

Offline redbaron

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Re: What causes case bulge?
« Reply #9 on: May 21, 2019, 04:45:49 PM »
Ok, I managed to get a couple pics of the bullets that had the bulge issues and get some measurements to see what's going on.


Here's the worst of them


I was trying for a crimp that measured .379" at the case mouth and these all measure .374". Except for the one with the blue bullet and the line running around the middle. For some reason that one has the worst bulge, but measures .380" at the case mouth. Not sure about that one

This next one shows a bulged round next to a dummy I made after adjusting the crimp die. I've got it set to just erase the bell which puts the crimp right at .380" at the case mouth. Made up a bunch of dummies using most of the different headstamps I have and they all plunked.



I ended up backing off the crimp die maybe a turn and a half, so it certainly wasn't ideally set, but that didn't seem like way too off.

Offline M1A4ME

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Re: What causes case bulge?
« Reply #10 on: May 21, 2019, 05:01:41 PM »
There are some brands of 9mm brass with a big difference in case wall thickness part of the way down.  If you look inside you can actually see a step at about the point where that canelure is on some of your cases.  Most folks recommend not even using that type of brass.  It can result in either damage to the base of a longer bullet, like your 147 grain bullets and a pressure change vs. cases that don't have that real thick wall.  A thick case wall decreases the case internal volume which increases the pressure.

Even if the brass doesn't have that visible thick ledge around the inside it WILL still be tapered thicker as your near the bottom.  That would also build increased pressure vs. cases with thinner walls.

With CZ's you usually have to load a shorter overall length (cartridge length) than with some other brands of pistols and that results in the 147 grain bullets being pushed even deeper into the case.  I pulled some old 147 grain hollow points out of M&P magazines yesterday and I was amazed at how long they were vs. what I was used to loading the last few years for my CZ's.  Got my new M&P 2.0 out, removed the barrel and those 147's loaded for the older 1.0 "plunked" just fine in the 2.0's barrel.  They barely look like 9MM ammo.  You can't do that with a CZ.


[Mods changed "may" to "will"]
« Last Edit: May 22, 2019, 12:15:24 PM by Wobbly »
Better to have it and not need it, than to need it and not have it.  So, if you see me walking the dogs with my SIG 556R, its okay.

Offline redbaron

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Re: What causes case bulge?
« Reply #11 on: May 22, 2019, 10:34:36 AM »
thanks for all the help guys. I think I might go through my brass stash and get rid of the cases with the cannelure just to make my life easier. It's not like I'm hurting for 9mm brass :D

I also ordered one of the 100 round Shockbottle case gauges, so I can add that step to my process now. It should be more convenient than plunking every round in a dismounted barrel

Offline Wobbly

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Re: What causes case bulge?
« Reply #12 on: May 22, 2019, 12:32:19 PM »
Most folks recommend not even using that type of brass.  It can result in either damage to the base of a longer bullet, like your 147 grain bullets...


I have read this thread 3 times looking for a statement where the OP tells us he's loading 147gr bullets and don't see it. The photos certainly look like 147gr at that seating depth.

I don't even see a brand of bullet mentioned.

Maybe I'm blind.
In God we trust; On 'Starting Load' we rely.

Immature reloaders ask: What's wrong with this gun?
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Offline redbaron

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Re: What causes case bulge?
« Reply #13 on: May 22, 2019, 12:36:13 PM »
They're not 147s, they're 124 gr hollow points that I cast myself, using this mold: https://bit.ly/2ETav41

Offline redbaron

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Re: What causes case bulge?
« Reply #14 on: May 22, 2019, 02:08:29 PM »
Looks like I forgot to supply some info so I'll remedy that now

Firearm
Canik TP9 SFX and CZ 75 SP-01

Components
Cast 124 Gr HP 9mm
Case: variety


Reloading Equipment
? Press brand and type:  Dillon 550C
? Dies:  Dillon



 

anything