Case head separation?

[Bart B.]

Reynolds, thanks for pointing me at the original picture that I cannot open to see.

All of my rimless cases have that bright ring about 2/10ths inch in front of the case head. They're caused by the brass pressing hard at that point forward from peak pressure. Behind that point, the case tapers back too the diameter at the extractor groove where the brass is the thickest; it doesn't expand much in that area. But none have that shallow groove under it inside the case; head separation hasn't started. My resized rimless cases have less than .003" head clearance when fired to prevent such things.

[mehavey]

I ran a tiny screw driver (flathead) inside the case and I didn't feel a notch...

The screwdriver won't do it.
- Take a paperclip
- Straighten it out
- Bend one end at 90°
- Lightly file to a sharp point.



Insert that into the case.
It will pick up any groove that's starting.

[mardanlin]

I managed to get the photo smaller. Hopefully it works this time. As I said, I tried the paperclip test and I did not feel a ridge, and it appears to be lower on the case than the other case-head separations I've seen, that's what lead me to ask.

Is it possible that it's a bulge resulting from being resized so much? Is there just an accumulation of brass at the bottom? I thought that FL dies pushed the brass upward, hence the need to trim, but I've also heard of belted magnum cases developing a bulge at the bottom, so I'm not sure.

The bulge is rather sharp though. It's not really round if that makes sense, it's kind of like an A sticking out of the side.

EDIT: I just read the post above and saw I was doing the paperclip test wrong. I will find an actual paperclip tomorrow and try that.

[Bart B.]

That picture tells me the chamber is much larger than the case at that ridge line. If you can neck size the fired cases, they'll last longer. But will need to be full length sized once in a while.

It's not caused by sizing or firing a case too many times. It doesn't happen that much when the diameter difference of case and chamber at that place is minimal.

I enlarged the body part of a full length .30-06 die a friend used with his M1903A3 whose chamber was bigger than normal. He was able to get 20+ reloads per case minimally setting the fired case shoulder back a smidgen each time. Sharpened edge of a 16d nail head didn't find any head separation grooves inside the case in that area.

That ridge is where the brass goes from thick to thin and expands more from pressure. Sizing squeezes it back down then shooting pushes it back out. Like a wire clothes hanger being bent and straightened out, it soon breaks. You need to minimize that bending.

If you could measure a new case diameter at that point, shoot it then measure again on that ridge line, the difference would be interesting to see.

[F. Guffey]

Mardlin, , this should be post #30, by the time a thread gets to response #30 the question should have been asked “What receiver design?” If you had posted the information about the ‘bulge’ being on one side and not the other I could have guessed what receiver design you are using.

I have purchased fired cases at ‘A’ rifle range, they provided me with enough room to sort cases, I did not make it home with a pile of cases I could not use. A case fired in rifles with ’the large claw’ put pressure on one side of the case and the opposite side did not have support once the bolt was rotated/closed. I expected cases fired in in that type of chamber to have a (what appeared to be) dent on one side or what appeared to be a bulge. And I would not expect the chamber at the rear to be round.

While sorting cases for length from the shoulder to the head of the case my judgment was questions, seems the slights dent and or bulge was reason enough to reject the case. At .10 cents each plus a bonus case for every 10 cases I purchased plus the cases that had been fired in trashy old chambers allowed me to size cases for long chambers without fire forming.

Then there is the difference in case color, I measure unsupported case head from the face of the barrel.

F. Guffey

[reynolds357]

All this argument about setting up sizing dies makes me glad I primarily neck size.
I do some full length sizing primarily on hunting rounds, but I still stick mainly to the old and antiquated tradition of neck sizing. I do not think I have even used the Full length dies in my sets for my BR guns. On occasion I have to bump them with a body die, but I always do the body and neck in two steps instead of using a single die. When I do reload for my rifles with a Full length die, 99% of the time I set them up to the press camming over hard against the die. I always cut my chambers where the go gauge just barely goes.

[F. Guffey]

And I am glad I am not in love with myself.

F. Guffey

[Bart B.]

Reynolds, how much shorter are your cases (head to shoulder) than your rifle's chambers are?

Just curious as to how much your case shoulders are set back when you full length size them with the press camming over when the shell holder stops hard against the bottom of the sizing die.

[603Country]

I was wondering the same thing that Bart is. I'd be concerned about sizing the brass a bit too much. The good news is that if the brass is being sized too much, the ensuing case head splits will tell you that. And if you don't get case head splits then you are likely not over sizing (pushing the shoulder too far back). It all depends on the match of your die to your chamber size. Sometimes it's just like Goldilock's porridge, in that it's just right.

[F. Guffey]

Reynolds, how much shorter are your cases (head to shoulder) than your rifle's chambers are?

Bart B., he did not leave any tool out, the only thing he left out was the length of the chamber from the shoulder to the bolt face, the length of the case from the shoulder to the case head and the length of the fired case from the shoulder to the head of the case.

And he neck sizes, if everything he says is correct the difference in length the chamber and case if .005" with the bolt just closing without slight resistance to closing.

F. Guffey

[Bart B.]

I don't care about case or chamber lengths that are probably straddling 2.500" by several thousandths.

[schill32]

mardarlin

I had this on my cases that I fired in my M1 and it looks to me from your pic its normal. It comes from when you resize your cases, it comes from where the die stops at the bottom of the case ,had other reloaders comment on this and they say this is NORMAL providing there is no crack starting, look under a magnifying glass to see a hair line crack and the bent over paper clip for inside the case , it comes from too much pressure in the case when fired the like your bullet shoved into the lanz or over max load at that point the case is junk.
Shooting a semi auto rifle all cases should be full length sized .
I hope this helps
Steve

[Bart B.]

All new rimless cases I've seen after their first firing have that ring. It's the largest diameter part of the case. It gets sized down a bit on its first trip all the way into a full length sizing die.

Same thing with my new belted cases but that part usually doesn't get sized down with conventional full length dies.

[reynolds357]

Guffey, you sure you are not in love with yourself?

It is amazing that the instructions that come with every brand of die manufacturers dies are all in error about how to set up their dies. As I said, on my target rifles I neck size. When I have to set up a body die for a rifle or re-barrel, I set it up to just return the case to the point it is no longer sticky. I actually do not measure anything except OAl. I set the body die up by the feel of the case in the chamber.
I mostly neck size my hunting brass, but when I do full length size hunting brass, I usually cam the press over. My case life factor in all my hunting rifles (except my lever guns and break action pistols) is usually primer pocket. Sometimes a neck will go, but rarely. The only times I have had case head separation has been in wild cat load development and when I was Pushing a .264 Win mag way yonder past max load.

[mardanlin]

Thanks Steve, that's good to hear from another M1 shooter.

[F. Guffey]

I don't care about case or chamber lengths that are probably straddling 2.500" by several thousandths.

Bart B., I know you do not care, but do you understand he is saying he is closing the bolt on a go-gage, and the go-gage does not have a neck, in a fashion the go-gage measures the length of the chamber from the shoulder/datum to the bolt face.

Your question:

Reynolds, how much shorter are your cases (head to shoulder) than your rifle's chambers are?

In the perfect world the difference between the case length from the shoulder/datum to the case head and the chamber from the shoulder/datum to the bolt face would be .005" before the minimum length/full length sized cases is chamber and fired..

After firing the case (fire formed) length from the shoulder/datum to the case head should the same length as the chamber, less the proverbial case snap back/shrinkage.

Then there is sizing after firing, again, who measures? I do.

F. Guffey

[F. Guffey]

Reyonalds357, please forgive, I based my assumption on "I". Your last post has at least 8 sentences that start with "I".

Methods and techniques, how and why. I am not so hard headed I insist on following the instructions, there is something beyond the instructions. I am the fan of cutting down on all that case travel.

F, Guffey

[Bart B.]

For a .30-06, I'd prefer .002" head clearance (difference between chamber headspace and case head to shoulder numbers) because. . .

The case usually ends up with .003" to .004" more head clearance (sometimes moreso) when the round fires. Which means the back of the case will stretch about .005" when fired.

When resized back to the original dimensions, that same cycle starts all over again. Head separation issues happen if there's more head clearance for a loaded round. Case life is limited.

[mehavey]

For a .30-06, I'd prefer .002" head clearance (difference between chamber
headspace and case head to shoulder numbers) because. . .

The case usually ends up with .003" to .004" more head clearance
(sometimes moreso) when the round fires....

I assume you mean in the Garand (because of the chambering forces involved -- as opposed to firing pin impact)...?

[Bart B.]

Mehavey, that .002" head clearance is for both Garands and bolt guns. There's a little bit of case shoulder setback as the Garand's bolt slams the case hard against the chamber shoulder when it goes into battery. Hammer spring strength and firing pin protrusion from the bolt face do most of it. I've fired new .30-06 ammo in Garands with new cases having that much head clearance as checked with gauges measuring both ammo and chambers. Flawless functioning.

With bolt guns, hardly any shoulder set back comes from closing the bolt, if at all. It's all with firing pin impact from spring strength and firing pin protrusion from the bolt face.

[mehavey]

There's a little bit of case shoulder setback as the Garand's bolt slams the case hard against the chamber shoulder when it goes into battery. Hammer spring strength and firing pin protrusion from the bolt face do most of it.

With bolt guns, hardly any shoulder set back comes from closing the bolt, if
at all.

That was my thinking as well, though I would have considered the reverse
in predicting the impact of bolt closure vs hammer/pin in the Garand.
~~~~~~~~~~~

BREAK BREAK...
As far as the OPs original question of "how to determine sizing die setting" for minimal case rattle-room,

- Bolt action: Adjust the die body down until the unloaded case will just allow the bolt to close.
That can be done each time you start a loading session w/o regard to any precise measurements
as long as you are using brass of same brand/lot#/same firing history.
(Bolt actions have the advantage of gentle/human camming force to ensure proper closure.)

- Gas gun: Take the extra time to strip the bolt and determine exact case headspace dimension
that allows the bolt to close freely. Ensure the die produces that dimension (-0.002") each loading
session. This takes either a Precison Mic and/or a headspace gauge set and a set of calipers.

[Bart B.]

Note that shoulder setback is more with soft case brass and hard primer cups; less with the reverse.

My first ever measurements of primed case shoulders setting back was with a Garand. I was amazed at what I saw happen using new commercial .30-06 cases as well as new LC match cases. Commercial ones' shoulders set back a bit more on average than match cases; about .0006" as I remember.

Depending on the extractor's surface and spring strength as it slides over a case rim, that could have some influence on the total force put on the case head driving the case shoulder into the chamber shoulder. I made no tests regarding the extractor's contribution to chambering the round.

[F. Guffey]

I just love it when members become so chummy.

http://www.vocabulary.com/dictionary/initiative

Initiative, I take the initiative, for that reason I can not be chummy, because I disagree. When the bolt closes in a Garand the firing pin is at the rear, because? it floats. So let us make-up something to call it because the firing pin is not protruding from the bolt when a round is chambered the bolt must be something like slam, after the bolt slams the case into the chamber the firing pin is sure to follow, let us call that bam. Catchy, slam/bam.

Every cease fire on the firing range with a Garand required ejecting a chambered round, with out fail the ejected round had a dent in the primer, not a big dent, just a small dent, nothing like the dent my M1917 firing pin falling on a primer, the firing pins in my M1917s are not bashful, they do not make that baby click, they make the BIG CLICK!, when the primer fails to fire the dent is huge, my firing pins crush the primers.

Initiative? Remove the firing pin from the M1 Garand bolt, pull the bolt back as far as possible then let go, measure the case length from the shoulder to the case head, if the case length was not measured before chambering , start over. OR, Load an inert round to chamber after firing (with the firing pin installed) then measure again.

OR, pretend you are at cease fire with a chambered round, if the case was measured before chambering the effect of chambering can be measured, it does require a small amount of initiative, it beats “as I remember”.

Then there is that part I remember, the M1, the 03 Springfiled and M1917 were feed out of the same can, oversight on the part of GARAND? No. In the big inning there was an M1 Garand 30/06 chamber reamer and there was a 30/06 chamber reamer for the 03 and M1917. Now after all these years I have to ask: Why were there two different reamers in the big inning and in the last inning reloaders are sizing going to the extremes like “I use a small base die because etcetera.

F. Guffey

[mehavey]

I believe Bart's point was that bolt closure forces had relatively little effect upon case
shoulder dimensions as compared to the force of the hammer driving the firing pin into
the hard surface of a military-grade primer cup -- that then drove the soft brass case
shoulder up against the stops in the steel chamber before powder burn took hold.

Significant shoulder setback therefore ocurred upon firing, not before.

[F. Guffey]

I believe Bart's point was....

Mehavey, thank you for the explanation. I have read the sequence of events explained by him from pulling the trigger etcetera, etcetera. He did not understand the firing pin in the Garand is in it for the rife when the bolt closes. He did not understand the slam bam, and that is OK by me, I do not place a demand on anyone to ever make an attempt to think about it. Asking Bart B. questions only confuses him.

I know at the end of the day Bart B. will be hollering the same thing with total disregard to distance and time, that is not my problem, I am the fan of cutting down on all that case travel.

F. Guffey