What causes case bulge?

[recoilguy]

In my humble opinion if it were me I would check 2 things because it is where I have experienced similar issues:

1 - the first die - deprime resizing die, if the gap between the bottom of the die and the shell plate is not correct bulging at the bottom of the shell can be imparted on the down stroke. It then can not be corrected in the following steps
2 - The 3rd die - the seating and crimp die - If the die starts the tapering (crimp) too soon before the bullet is seated to depth I would get occasional bulging and it would happen as often as you described. All the other factors described and asked for in this thread played into getting those two things right for me. I never start pulling the lever for production, until I know my dies are set perfect for the bullet size shape and weight I am putting together.

I am not an expert nor an advice on reloading go to guy. I have reloaded more rounds then I can even begin to count ( I can count to at least 40,000) and I experianced bulges twice. Each time for different reasons which made it a bummer but both times I remedied the problem. Dies are tricky and precise

You now have heard my experience with the problem, do not misconstrue it for advice or even intelligent banter......take it for what it is, a story about my experience with a similar problem and what I discovered.

RCG

[andrew1220]

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.

I'd bet $100 the cases on the right with the cannelure/crimp around the case, are Aguila? and the cases on the left are CBC/Magtech? Those along with X-treme, FM (freedom munitions), IMT, AMERC, Tula brass, and a few others should NOT be used with longer/heavier bullets like the 147's. I scrap all of those headstamps. I'm also using 147 gr RN blue bullets. I visually inspect every case to verify headstamp (and caliber) before it goes on the press.

[redbaron]

The ones with the band are indeed Aguila, but the one with the black bullet and no band is also Aguila... Go figure on that one. The others are FC, CBW, and CBC. The kicker is I checked the other rounds I did recently and there are rounds from every one of those headstamps (even the Aguila with the cannelure) that plunk just fine and have no noticeable bulge when I look at them

Also, I'm not loading 147s. All my 9mm are 124gr. cast lead that I did myself. I've been using this bullet for about a year and it's the first time I've had issues

[redbaron]

Just checked my mailbox and my case gauge got here. I took a few pics to show how things look with it. At this point I've gone through every round I have loaded and plunked them all in the tightest chamber I have (the Canik). I haven't found any other egregious bulged cases.



Even though they don't all sit flush in the case gauge, they all plunk and spin freely. I even carefully hand cycled the ones that were sticking up the most and they cycled just fine

Here's two of the ones with the monster bulge in the gauge just for reference


There is one thing I can think of that may be the variable in all of this. I loaded about 150 rounds with the stock Dillon powder funnel/expander. Then I bought a custom one that expands like a Lyman M die and proceeded to load another 150. Since I keep my ammo loose in an ammo can I don't know if the bulged cases came from when I used the stock expander or the custom one.

I may load up another 100 with the setup as it is and see if I get any more monster bulge cases, but I've double checked the setting of everything else and don't really know what else to adjust

[Tenbones]

I'm rather surprised at the variation in case length of your finished rounds....

[tdogg]

Just checked my mailbox and my case gauge got here. I took a few pics to show how things look with it. At this point I've gone through every round I have loaded and plunked them all in the tightest chamber I have (the Canik). I haven't found any other egregious bulged cases.



Even though they don't all sit flush in the case gauge, they all plunk and spin freely. I even carefully hand cycled the ones that were sticking up the most and they cycled just fine

Here's two of the ones with the monster bulge in the gauge just for reference


There is one thing I can think of that may be the variable in all of this. I loaded about 150 rounds with the stock Dillon powder funnel/expander. Then I bought a custom one that expands like a Lyman M die and proceeded to load another 150. Since I keep my ammo loose in an ammo can I don't know if the bulged cases came from when I used the stock expander or the custom one.

I may load up another 100 with the setup as it is and see if I get any more monster bulge cases, but I've double checked the setting of everything else and don't really know what else to adjust

I don't own a case gauge.   I rarely even plunk test rounds in my chambers.  I do measure the oal of my competition cartridges.   So take what I'm about to say with a grain of salt.

If I had that much variation in my loads as you have shown here with the shock bottle,  I'd be going over my die setup again.   Something isn't set properly or your right arm needs a big lesson in consistency.  Start with the sizing die and work your way to the crimp die.

The sizing die should be just kissing the shell plate, or just off by about .003".     Make sure your expanding the mouth enough to place the bullet.  Make sure your not crimping while trying to seat the bullet as most seating dies will crimp if adjusted to do so.  Set the taper crimp die to .378".

Good luck.

Cheers,
Toby

Sent from my SM-G950U using Tapatalk

[redbaron]

Here's where I stand so far. Tdogg, I took your suggestion and reinstalled all the dies in the tool head, I made sure I was following the instructions in the Dillon setup paper exactly. I used a piece of Winchester  brass for the die setup since that's what I have the most of.

I got everything adjusted so that first dummy would sit flush in the case gauge, so I then got two pieces of every other headstamp I have and loaded dummies with them.

Some brass did not want to sit flush in the gauge, but they were all from the same 3 headstamps. I feel pretty good about that because it suggests it's the brass and not my process at this point. Aguila, CBC and PPU did not want to work, but I was expecting Aguila and CBC not to, and I don't have enough PPU to really have any other evidence. Both pieces of it I tried didn't work so that doesn't make me feel too highly towards it.

Otherwise, around 7 other headstamps worked just fine.

I'm going to do the test again with different samples of the headstamps that work just to verify, but I'm feeling pretty confident at this point

[Wobbly]

We've seen issues with those multi-hole gauges before. There's simply no way you can make 50 identical gauge holes.... no matter what their marketing dept says.

Back to the LE Wilson single hole gauge.

[redbaron]

I was having the same thought, so I used the same hole to test everything in and then confirmed by plopping each round in a couple random holes too. It may not be the most consistently accurate gauge but it should at least let me spot any future major problems

[M1A4ME]

I've seen some "bulge" from the sizing die vs. the bullet/or the brass wall thickness??

I used to use a set of Lee 9MM dies with a carbide sizing die.  Very DOGGONE difficult to resize the cases.  It was like resizing rifle cases.  Pain in the butt!!  The 9MM ammo loaded with those dies had a coke bottle look to them.  The case was small just below the bullet, larger near the base and at the top where the bullet was pushed down into the case.  The all chambered, fired, ejected just fine.

I got tired of wearing myself out resizing pistl brass and bought a set of RCBS 9MM dies with a carbide resizing die.  Easy peasy.  No for straining to get pistol brass resized and no more coke bottle looking cases after the bullet was seated.  And the all chamber, fire and eject just fine.

The Lee die was squeezing them down farther/smaller OD than the brass really needed to be resized.  I gave the Lee dies to my youngest son.  I big strong 6'2" 245 lb. diesel/generator mechanic/electrician/technician.  I'm sure he won't notice the effort required to resize his 9MM brass.

[Wobbly]

The case OD has only the Max Dia dimension to be concerned about. You can size the cases much smaller, and of course they still fit inside the chamber just fine.

The 9mm case is tapered, and so the sizing carbide also should be tapered. I highly suspect that Lee cheated a little and used a straight piece of carbide. That would make the middle of the case much smaller than needed and make it appear highly constricted once the bullet was seated.

It's not pretty, but it works.

[Bossgobbler]

How deep are you seating the bullets? with a 0.358" sized bullet if you seat it very deep you will start to push the middle of the case out(bulge) Also what is the length of your bullets?

[Grendel]

I am having a similar issue with about 1 in 3 or 4 of my 45/70 reloads. I'm using Win once fired brass and Speer 300gr bullets over 55gr of IMR 3031 on my Lee Classic Turret. Every so often, I'll get a bulge just where the bullet has seated which prevents the completed round from entering the case gauge fully. I have to break the round down and resize it and then very carefully reseat the bullet.

I'm trimming all the brass to 2.095 and seating to a total OAL of 2.550. The bullets are .458cal.

It's aggravating, to say the least

[Wobbly]

Every so often, I'll get a bulge just where the bullet has seated which prevents the completed round from entering the case gauge fully. I have to break the round down and resize it and then very carefully reseat the bullet.

I'm trimming all the brass to 2.095 and seating to a total OAL of 2.550. The bullets are .458 cal.

? Is that the proper "trim to" length ? I don't have a book in front of me.

? Also, are you chamfering the inside of the case after trimming to make sure the bullet doesn't catch  on the extremely sharp inside edge of the case mouth ?

? Have you tried screwing the BODY of the seating die out 1/8 of a turn to omit any bullet crimp from going on ?

[Grendel]

Yes

Yes

Not yet, but that's next on my list. It's strange that it's not every round, but only 1 in 3 or 4. I'm wondering if it's slight discrepancies in the bullets, I should probably check them for length too.