Why Some (9mm) Cases Don't Size Right?

[otisrush]

After getting through my 9mm fit issues that many here helped with (I'm referring to my thread a couple of weeks ago about getting stuff to fit my PPQ https://www.thehighroad.org/index.php?threads/9mm-case-gauge-pass-plunk-fail.825609/ ) I've made a minor change to my process.

I now drop the just-sized case into the case gauge to ensure it sized correctly. I used to drop finished rounds into the gauge. (I know the gauges don't check COL. I was checking fit in general.) And when I'd do that on finished rounds there were some rounds that officially didn't pass (they stuck out a little) but they'd work/fire anyway. But with this process change I've tightened what I consider "pass".

In the above referenced thread people report that they toss stuff that doesn't pass their case gauge after sizing. A couple of people reported upwards of a 10-15% toss rate from range pickup brass. Since changing my process I'm getting more tossed cases than I thought I would, but probably <5% end up getting the heave-ho.

I have two questions:
1. Why would a case not size correctly? Cheep brass? Old brass? I definitely seem to be finding if I'm tossing a case it's either S&B or Win. Those seem to be the ones with the highest sizing failure rate.
2. I'm intrigued if this issue of cases not sizing "completely" presents itself with folks who use progressive presses. I'm using a RCBS Rockchucker so I'm doing this checking in between manual steps. I get the sense that, once set up, every round that comes out of a L'N'L or a Dillon works just fine. If that's the case, is doing a case gauge check on every case after sizing overkill?

Maybe I've answered my own question in that my rounds worked before I made this change - which would mean manufacturers tend to make their chambers a little "loose" (I'm not commenting on length....but rather diameter) relative to SAAMI.

These things are bugging me and I just want to understand it better.

Thanks.

OR

 

[Dudedog]

For #1
One reason can be the very base of the case does not get resized with a normal sizing die regardless of press type.
A roll sizer or a push through (bulge buster) can get the very bottom but no way to do it when it is held in a shell holder/shell plate.

I don't case gauge my 9mm but none of my pistols have really tight chambers.

 

[RugerOldArmy]

You may be aware of this already:

- Adjust your sizing die until it touches the shellplate.
- Turn it an additional 1/4 turn, so the press 'cams over'.

Doing this, I've never experienced a 9mm case not sizing fully, in 10s of 1000s of reloads on my Dillon 550 with Dillon carbide dies. I use a LOT of S&B and Win brass. The only thing I've noted peculiar to these is that S&B has a little tighter primer pockets.

If you're already doing this, you've run into something I've yet to see, and am interested.

 

[Walkalong]

1. Why would a case not size correctly?

Sizer not set up correctly. Be sure the sizer is all the way down when actually sizing a case.
Hot loads that expand the web, not just the over stressed "9MM Major" brass inconsiderate people leave laying around.
The sizer cannot size the web because of the mechanics of shell holder/plates/sizers/carbide inserts. Some dies are better than others at getting low on the case.

I've never experienced a 9mm case not sizing fully,

By sizing fully do you mean it will fit a Wilson case gauge? Will fit your chamber/s? Lots of big 9MM chambers out there. The brass that would not fit my Wilson gauge/SA EMP would happily chamber in my other 9MM guns. Do you mean documented once fired range brass? Range pick up brass?

 

[johnandersonoutdoors]

I case gauge all my 9mm after resize/deprime and washing them. Out of a batch of about 1,000, I will only have 1 or 2 that will fail to fit my case gauge. I am not sure how many you are getting, but it shouldn't be too many.

 

[otisrush]

You may be aware of this already:

- Adjust your sizing die until it touches the shellplate.
- Turn it an additional 1/4 turn, so the press 'cams over'.

Doing this, I've never experienced a 9mm case not sizing fully, in 10s of 1000s of reloads on my Dillon 550 with Dillon carbide dies. I use a LOT of S&B and Win brass. The only thing I've noted peculiar to these is that S&B has a little tighter primer pockets.

If you're already doing this, you've run into something I've yet to see, and am interested.

Do you adjust for cam over using carbide dies? As I recall (I'm not able to go down and actually check them at the moment) is that camming over on carbide dies can cause the carbide sizing ring to break.

My non-carbide rifle dies (well - my .223 which I load for an AR) I set for cam over.

OR

 

[Taroman]

What the OP has are 9mm cases with a thick section in the middle.
They size down, but when the expander is run into it, the middle bulges.
Several imported brands use this sort of case, Aguila comes to mind.
I trash all imported brass.
Only load R-P, WW or Federal. Never a problem.

 

[otisrush]

What the OP has are 9mm cases with a thick section in the middle.
They size down, but when the expander is run into it, the middle bulges.
Several imported brands use this sort of case, Aguila comes to mind.
I trash all imported brass.
Only load R-P, WW or Federal. Never a problem.

When my sized 9mm cases fail the case gauge test it is before I bell the mouth. The ones that don't pass do so immediately after they are removed from the sizing die.

OR

 

[Ole Joe Clark]

I don't check them after sizing and before loading. I load mixed head stamp cases and drop every one into a chamber before boxing them up. If I find one that doesn't fit properly I will size the finished load again, (carefully), this usually fixes the problem. But I haven't had this problem in a while.

 

[Walkalong]

What the OP has are 9mm cases with a thick section in the middle.
They size down, but when the expander is run into it, the middle bulges.
Several imported brands use this sort of case, Aguila comes to mind.
I trash all imported brass.
Only load R-P, WW or Federal. Never a problem.

I load all manner of headstamps in 9MM brass. All the sized brass that fits the gauge works after loading. All kinds of headstamps have failed to size fully.

It doesn't seem logical that manufacturers would produce brass that will be too fat in the middle after seating a bullet. After all, they have to seat bullets to sell loaded ammo.

That said, for some brass if you seat bullets too deep it can bulge a bit more than optimum.

There are also some cases with a step in them these days and if you seat a bullet below that ledge it will bulge the case out too much.

The pics are .380, but show the bulge from the internal ledge when a bullet is seated below it.

 

[rfwobbly]

I have two questions:
1. Why would a case not size correctly?

► Obviously one of the biggest areas of concern is the rim area, where the die simply can't reach. Your percentage of defect will depend heavily upon where you find the brass you're using. Do you find your brass at a public range where general plinkers practice, or do you retrieve your brass from a private gun club ?

Private clubs often host competitions. If the competition allows Open Class with "9mm Major", then often times those brass will have the head of the case expanded to ~0.393". If you watch, you'll see those shooters never pick up their brass. They know it's toast !

 

[RugerOldArmy]

By sizing fully do you mean it will fit a Wilson case gauge? Will fit your chamber/s?

Yes, and Yes. The outer dimensions of a case conform to 9x19 SAMII spec...there is no Voodoo to it.

Most of my brass is Starline. Some was sold as once-fired. Some is range brass, from other shooters that didn't want it, or from Police practice that I get from my buddy's son (who is a cop).

Note that 9x19 is a tapered case, not a straight-walled case. .381 near the case mouth, .391 half an inch nearer to the web. Having the die size all the way down matters.

If you don't seek out brass shot from 9mm Major, or shoot damaged 9x19 brass, there should be no issue sizing an empty case, IMO.

In terms of seating a bullet after sizing, tell me I'm oversimplifying it by stating that, with appropriate bullets for the cartridge, you simply stay within the SAMII OAL, or seat a bit deeper based on the plunk test (set when you're testing the low end of the powder range).

No disrespect intended. It seems we're making this harder than it is. I doubt you're SA EMP chamber is below SAMII dimensions, or tighter than my Kimber Ultra Aegis II or Sig P210...it makes no sense to manufacture a pistol with a chamber tighter than SAMII...but yes, some manufacturers have more 'generously' sized chambers seeking reliability feeding.

The pics are .380, but show the bulge from the internal ledge when a bullet is seated below it.

.380 is a different animal...the case tapers .001" not .010" from .373 to .374 with the same size bullet. I can't speak to seating a bullet too deeply in one (in which you might consider if that bullet is really intended for .380) or brass offerings with a thicker 'step'. You're likely ahead of me on that, and those case walls are .0095 thick instead of .013 thick, so it makes sense that seating a bullet into a thicker section, and getting a bulge, might simply mean you're using a longer bullet suited more for 9x19 than .380. Can I make a guess that it was a 115 Gr bullet (about the biggest safe bullet for .380) which had a profile that caused it to fail the 'plunk test'? That might get you to the step, for a cartridge that normally shoots 85gr to 95gr bullets. At that point, is it a 'reloading problem' or an 'unsuitable component' problem?

When you get right down to it, the 'plunk test' is a way to determine your maximum OAL, below the SAMII OAL, that works in your guns. The OAL that works in ALL guns for that bullet profile may be a hair less, since the SAMII spec doesn't specify the shape of a bullet's curves...

 

[RugerOldArmy]

Obviously one of the biggest areas of concern is the rim area, where the die simply can't reach.

Look at a 9x19 case contour near the case web, and look at the Dillon Carbide die pics on the Dillon site. The carbide ring goes all the way down to the base of the .391 portion.

People resize .308 Win fired from M60(s) back to spec. I don't think actually being able to size it is the issue...the issue is that it was an abused case.

 

[Walkalong]

I doubt you're SA EMP chamber is below SAMII dimensions,

It was before I sent it to SA and they reamed it. It's at SAMMI minimum now.

.380 is a different animal...

It was only as a pic to show the bulge from the ledge both calibers can have now with some makers.

I don't think actually being able to size it is the issue...the issue is that it was an abused case.

Same thing really, won't size down because it has been expanded too much due to pressure. I have always posted that I felt the case was subjected to over pressure if they won't size down, which is why I scrap them.

In a way, if you count all the brands you automatically scrap, you have a lot more than a 10% to 15% case loss on range brass.

there is no Voodoo to it.

No there isn't.