Case mouth tension and side wall thickness tolerance

[Davehb]

Try to get my nomenclature correct:

Is there a point where case wall thickness becomes too thin?
Or bad mix resulting in weak cases?
 
So far just building test cases.
I’ve got resizing die, and expander dies set.

Setting up seating die to “crimp” (set some case mouth tension cause lot of thin walled brass wouldn’t hold bullet in place. I read taper crimp sticky couldn’t understand why some weren’t holding so was getting confused) I couldn’t put it at a set point, and crimp case mouth the same on all cases because of wide variations in case thickness.
 
After running into the issue I started measuring case wall thickness.
Some case’s running as thin as .0085 would result in .0085 x 2+.355=.372.
I’ve tried to search for minimum case wall thickness, or minimum cross distance for case to seat safely without slipping into riflings, but haven’t found it yet. 
 
Federal, Starline and few Winchester hold well without any crimping of case mouth. No setback with pushing it against bench without “crimping” for added tension.
 
My Setting for the expander results in a tight fit for most federal, all Starline and Hornady plated cases.

With the brass (non-plated) hornady (that I have) and some of Winchester cases I can actually turn the seating screw with my fingers to push the bullet in the case. Most of those cases are thin having a thickness of .0085-.0105”.

Maybe I got some bad lots of ammo? [emoji1743]
I know I have a limited time frame of once fired brass so maybe I got a few bad lots.

Old habit of keeping what little brass I shot, but never thought to keep lot numbers cause didn’t think I’d get into reloading again.
 
I decided to check something before posting think I figured it out but I’ll post this anyway in case another novice runs across it.

Still have some of one brand of live factory ammo the cases I’m having issues with came from.
It doesn’t take much pressure at all to set back the bullet, and factory cases are approximate .0098” thick compared to federal .0115.
I think I just got some cartridges with weak brass. my wife who doesn’t even have enough hand strength to rack a CZ75 without springs being changed to accommodate her can actually set the bullets back in the case with her little thumb pressure against a bench. 
Try as she might she is unable to do so with factory federals, or S&B xrg.

I was able to squeeze one factory round with pinch grip between thumb, and second joint of index finger pushing it in from 1.06” to 1.0415” OAL. Not all set back that easy but that one did.

Unable to do that with newer rounds from bottom of magazine.

[tdogg]

A couple of thoughts and questions.

Resizing the case imparts the case neck tension.  Improper case resizing could be the culprit.  How have you setup your resizing die in the press?  What brand die are you using?  What is the case mouth diameter after resizing?  Does it vary depending on case brand?

How you measure the case wall thickness can be tricky.  The case wall thickness varies depending on how far into the case you measure.  What brand of brass is measuring thin?

Taper crimp should be called case deflaring.  It isn't used to set neck tension.  It is used to remove the flare imparted by the expander (flaring die).  Too much flare could also lessen neck tension.  What is the case mouth diameter after expanding?  What is the case mouth diameter after crimping?

As mentioned by Wobbly and others here, we are recovering/still in the midst of a massive run on ammo.  Manufacturer's have been producing at peak capacity and thus some quality control issues are slipping through.  Being able to setback factory ammo isn't acceptable.  What brand ammo/case is able to be setback?

Cheers,
Toby

[M1A4ME]

Dies can be as different as ammo.

Not saying your resizing day may be bad.  Just saying they not all the same.

I started my 9MM reloading with a set of Lee dies with a carbide resizing die.  I eventually went to RCBS dies (also with a carbide resizing die) because resizing 9MM brass with the Lee die was like resizing rifle brass.  It felt like resizing .223 brass took less effort/strength.

I could also see the difference in the "bottleneck" appearance.  The Lee die sized the cases so much smaller that seating the bullet into the case left a very pronounced smaller diameter area in the case wall right under the bottom of the bullet.

Can't say all Lee 9MM carbide resizing dies will result in smaller diameter brass, just saying mine did.

And, could be your resizing die is a little on the loose side.  Not just ammo makers have a tolerance in their products but reloading equipment makes can also produce tools that vary in dimensions that result in variable reloads.

Good luck with it.

[Davehb]

A couple of thoughts and questions.

Resizing the case imparts the case neck tension.  Improper case resizing could be the culprit.  How have you setup your resizing die in the press?  What brand die are you using?  What is the case mouth diameter after resizing?  Does it vary depending on case brand?

How you measure the case wall thickness can be tricky.  The case wall thickness varies depending on how far into the case you measure.  What brand of brass is measuring thin?

Taper crimp should be called case deflaring.  It isn't used to set neck tension.  It is used to remove the flare imparted by the expander (flaring die).  Too much flare could also lessen neck tension.  What is the case mouth diameter after expanding?  What is the case mouth diameter after crimping?

As mentioned by Wobbly and others here, we are recovering/still in the midst of a massive run on ammo.  Manufacturer's have been producing at peak capacity and thus some quality control issues are slipping through.  Being able to setback factory ammo isn't acceptable.  What brand ammo/case is able to be setback?

Cheers,
Toby

I have to do some more checking. 
“Deflare” is the word I couldn’t think of.

They’re new carbide Hornady dies. 
Yes I’ve set up the die.

I.d. After resizing
Star line and federal brass .352-.3525
Brass causing problems after resizing case id of .3533-.354.
That’s why I was looking for specifications on case wall thickness. I remember reading some specs years ago (>30 years) there was a minimum where cases shouldn’t be resized and used. Sadly I don’t have any of my old books.
 
I’ve got to do some more measuring.

I did go out, without changing the die set up, and made 3 perfect test rounds using federal, and star line brass. No deflaring needed to hold the bullet.

Cases from Hornady custom, and some Winchester, are the main ones causing problems, and also the factory ammo that even my wife could push in.
I have no idea on lot numbers cause I’ve had them for a while. 
There were 3 in bottom of magazine (newer ones with deeper headstamp) that couldn’t be moved.
 
Case diameter after bullet seating without deflaring was running around .372-.375 on those cases.

Federal and star line brass after bullet seating and no deflare was running .375-.38.
Deflaring not needed.
I have the expander set shallow. Maybe .3555 where can maybe gets .001 into the case.

I could tell some things about slip through on qc. Got one post here on it.

[Wobbly]

Resizing the case imparts the case neck tension. Improper case resizing could be the culprit. 

This is not true.

You are concerned with holding the bullet in place. Holding the bullet happens on the INSIDE of the case. But the Sizing die only touches the OUTSIDE of the case. And, (as you have pointed out) different brands of cases have numerous different wall thicknesses. So you cannot set the case neck ID (inside diameter) by the Sizing die. And, due to the "springy" nature of brass, setting the case neck tension from the outside of the case is nearly a mathematical impossibility.

So what happens is the Sizing die shrinks the case mouth smaller than what is needed. Then, in a secondary operation, the case mouth (or "case neck") Expander comes by and expands the case mouth ID to the correct size.

If you are having issues with bullet retention, then all the corrective action is taken at the Expander.

You can prove this all to yourself by simply measuring your cases at different stages of the die work.

[tdogg]

Wobbly, I respectfully partially disagree .  If the case is not fully resized then there potentially isn't enough case neck tension to start out (as you pointed out with the statement "smaller than what is needed").  This is especially evident in a tapered pistol case such as 9 x 19 (which I assume is what the OP is discussing but it isn't explicitly shared).  Additionally, some pistol expansion dies don't actually resize the bullet bearing surface of the case neck.  They simply flare the case mouth open to accept a bullet (Lee Universal Expander).

This is why I asked How the resizing die was setup in my original post and what dies were used.

Cheers,
Toby

[Davehb]

With everything else being equal if brass is short on zinc it could create too soft a case to maintain stiffness.

I had 15 years in an auto machine shop specializing in cylinder head repair, and engine assembly.

Even though it’s been years ago still remember tolerances need to put in guides, cut seats for inserts, hone valve guides, and shrinkage from compression of components.
 
Since it seems to be batch specific, For myself; based on years of working with metals; I’ve come to conclusion the brass didn’t have a high enough ratio of zinc mixed in for hardness; They acted more like copper; Or the case wall was too thin at .0095 to have enough strength to give proper tension.
Unless I’m getting stronger in my old age 😀 cause I was never able to pinch factory rounds and push bullets deeper in the case before.
 
I cannot turn the seater screw by hand to seat bullet in any other cases. Just those I was having issues with.
I feel comfortable in saying I didn’t over bell.

I set expander to be the exact same size as the o.d. of the bullet +/-.0005

With the very slight curvature of bullet bottom, and the slight bevel created by deburr of case i.d. I got perfect centered alignment for the press. (Did have to change it to accommodate the larger (softer plated) o.d. Berrys last night).
 
Maybe Winchester, and Hornady both purchased brass ingots from same place, except I don’t think that would explain why they are all so thin 🤔
 

[Wobbly]

Wobbly, I respectfully partially disagree .  If the case is not fully resized then there potentially isn't enough case neck tension to start out (as you pointed out with the statement "smaller than what is needed").  This is especially evident in a tapered pistol case such as 9 x 19 (which I assume is what the OP is discussing but it isn't explicitly shared). 

Of course ! You can buy the best dies on the market and if you don't set them up correctly then you might as well go home. Dies need to be properly adjusted at installation. That sort of goes without saying.

Short of bad setup, are you aware of any name brand pistol Sizing Dies that don't take the case mouth undersize? I am not.

Additionally, some pistol expansion dies don't actually resize the bullet bearing surface of the case neck.  They simply flare the case mouth open to accept a bullet (Lee Universal Expander).

I respect what Lee has done for the entry-level reloading market, but they are also the best at soaking the American public with money grabbing gizmos and gadgets that don't really do much or perform as well . One of these is their FCD, another is their balance beam scale, and yet another are these "case mouth expanders". They are nothing more than wedges. They may be labeled "expander" and they can do "belling" OK, but they are not "Expanders" in the traditional sense.

The Lee "Powder Through Die" does the expansion and belling, much like the Dillon "Powder Funnel" does. And that's what my post shows.

[Davehb]

This is factory round I squeezed in by hand.


For comparison here is good factory round

 
I haven’t pulled any to check case thickness, but i can’t get the one above to move no matter how hard I push.

[tdogg]

Wobbly, I respectfully partially disagree .  If the case is not fully resized then there potentially isn't enough case neck tension to start out (as you pointed out with the statement "smaller than what is needed").  This is especially evident in a tapered pistol case such as 9 x 19 (which I assume is what the OP is discussing but it isn't explicitly shared). 

Of course ! You can buy the best dies on the market and if you don't set them up correctly then you might as well go home. Dies need to be properly adjusted at installation. That sort of goes without saying.

Short of bad setup, are you aware of any name brand pistol Sizing Dies that don't take the case mouth undersize? I am not.

Additionally, some pistol expansion dies don't actually resize the bullet bearing surface of the case neck.  They simply flare the case mouth open to accept a bullet (Lee Universal Expander).

I respect what Lee has done for the entry-level reloading market, but they are also the best at soaking the American public with money grabbing gizmos and gadgets that don't really do much or perform as well . One of these is their FCD, another is their balance beam scale, and yet another are these "case mouth expanders". They are nothing more than wedges. They may be labeled "expander" and they can do "belling" OK, but they are not "Expanders" in the traditional sense.

The Lee "Powder Through Die" does the expansion and belling, much like the Dillon "Powder Funnel" does. And that's what my post shows.

I'm not aware of any brand that doesn't size enough when properly setup with good components.  In fact they all probably size down too much knowing that the expansion step can be used to flare the case mouth open enough to stuff a bullet in the case.  In fact I used the Lee undersize die loading for 40 S&W due to issues with a bunch of pull down bullets being undersized and me seeing setback issues.

I'm not advocating for Lee universal expander usage but it is out there and folks use it.  I'm partial to the Lyman M stepped type of expansion as I now have a bullet feeder on my Dillon.  It makes the process run much smoother.

Cheers,
Toby

[Wobbly]

I haven’t pulled any to check case thickness, but i can’t get the one above to move no matter how hard I push.

• Obviously, that factory is having QA issues.

• You need to get over "checking case thicknesses".

[Davehb]

I haven’t pulled any to check case thickness, but i can’t get the one above to move no matter how hard I push.

• Obviously, that factory is having QA issues.

• You need to get over "checking case thicknesses".

Yes sir they were.


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