Dies for Bumping Shoulder
- Thread starter ninosdemente
- Start date
RC 20,after reading your description of how cases fail...I havea different way of seeing it.
I'm not saying you are wrong,I just see it different.
For the purpose of this discussion,lets leave out headspacing on the extractor and out of spec firearms.
To close the bolt easily,we have some head clearance.Not a lot,but some. Agreed?
Some feature,whether it be rim,case mouth,belt,or shoulder,limits the head clearance going forward. The bolt face and lockup limit the rearward head clearance. Still good?
The firing pin whacks the primer.the case makes contact with whatever surface limits forward travel. The "Anvil".
The primer ignites the powder,and pressure within the case rises.
Still agree?
So,with the case forward,where is the thinnest brass,or,where does the brass begin expanding,obturating,to seal on the chamber first?
Its thinnest at the neck and the forward part of the case,like,right behind the shoulder.
And,it gets thicker farther to the rear, nearer the web. Still good?
As the pressure builds,the obturated case actually gets a good grip on the chamber walls. PO Ackley published his observations in "Handbook for Shooters." He took the locking bars out of a 94 Winchester and the brass bturation held the breech closed.
So,the thin walled brass is gripping the chamber wall. The barrel is not stretching. Everything is good . But wait!! We have head clearance and pressure is up there.The case stretches till the case head is supported by the bolt face. The chamber does not stretch,so the forward part of the brass has the friction to stay where it is.
Till you get back to that thick part of the brass,with not so much friction on the chamber,you know,right where the case fails. And that's where the brass case gets pulled like taffy. Its over a short length. Pressure keeps the brass against the chamber wall,and as the case stretches,it thins.Ever do the "Paper clip test"? You feel that stretch ring like an O ring groove.
Cut a case with a stretch ring and look.
It might be that very thin section will crack during resizing,but the stretch ring came during firing,not in the loading press.
And .005 or .007 head clearance can pull a deep stretch ring in 4 or 5 firings.
We do a lot better at .002. Much less stretch. Maybe we'll lose cases to split necks or loose pockets before that darn head separation happens!!
Anyway,thats how I see it.
I'm not saying you are wrong,I just see it different.
For the purpose of this discussion,lets leave out headspacing on the extractor and out of spec firearms.
To close the bolt easily,we have some head clearance.Not a lot,but some. Agreed?
Some feature,whether it be rim,case mouth,belt,or shoulder,limits the head clearance going forward. The bolt face and lockup limit the rearward head clearance. Still good?
The firing pin whacks the primer.the case makes contact with whatever surface limits forward travel. The "Anvil".
The primer ignites the powder,and pressure within the case rises.
Still agree?
So,with the case forward,where is the thinnest brass,or,where does the brass begin expanding,obturating,to seal on the chamber first?
Its thinnest at the neck and the forward part of the case,like,right behind the shoulder.
And,it gets thicker farther to the rear, nearer the web. Still good?
As the pressure builds,the obturated case actually gets a good grip on the chamber walls. PO Ackley published his observations in "Handbook for Shooters." He took the locking bars out of a 94 Winchester and the brass bturation held the breech closed.
So,the thin walled brass is gripping the chamber wall. The barrel is not stretching. Everything is good . But wait!! We have head clearance and pressure is up there.The case stretches till the case head is supported by the bolt face. The chamber does not stretch,so the forward part of the brass has the friction to stay where it is.
Till you get back to that thick part of the brass,with not so much friction on the chamber,you know,right where the case fails. And that's where the brass case gets pulled like taffy. Its over a short length. Pressure keeps the brass against the chamber wall,and as the case stretches,it thins.Ever do the "Paper clip test"? You feel that stretch ring like an O ring groove.
Cut a case with a stretch ring and look.
It might be that very thin section will crack during resizing,but the stretch ring came during firing,not in the loading press.
And .005 or .007 head clearance can pull a deep stretch ring in 4 or 5 firings.
We do a lot better at .002. Much less stretch. Maybe we'll lose cases to split necks or loose pockets before that darn head separation happens!!
Anyway,thats how I see it.
I agree but how do the cases fail ? I don't see that in there , If the primary reason is not to much head clearance . What other normal part of case prep will cause case failures more often then to much head clearance over multiple loadings ?
Your explanation above and this below
is exactly how I got theses
To much headclearance over multiple loadings ( 3 ) is what caused my case failures . I had to much headclearance because I adjusted my dies as instructed by redding and has been the only time I've had case head separations .After learning how to adjust my FL sizing die to size a case to any specific rifle resulting in minimal head clearance I have not had another case head separation . So now I do all the other case prep stuff while minimally sizing my cases ( head to datum ) and have not even come close to another head separation . I conclude that " The normal push of following the die mgs instruction is what causes the case to crack above the base in short order. " which is screwing down the FL sizing die until it makes contact with a/the standard shell holder then an extra 1/4 turn or so . Is by far more likely to cause case failure over multiple loading then ANY other one thing in case prep . Agreed ?
So in conclusion I agree with both quotes .
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Those are stretch rings gone to the point of breaking through.Saw them lengthwise. You might discover them at the press,but the damage was done upstream .
If you prefer not to click links,go to Varmint Al's Website.
On the left column,select the article on "Chamber finish"
If you scroll roughly halfway down,there will be a finite element analysis cartoon labeled "rough chamber finish" and "friction co-efficient 56
Watch the cartoon and you will see how the stretch happens,
http://www.varmintal.com/a243z.htm
If you prefer not to click links,go to Varmint Al's Website.
On the left column,select the article on "Chamber finish"
If you scroll roughly halfway down,there will be a finite element analysis cartoon labeled "rough chamber finish" and "friction co-efficient 56
Watch the cartoon and you will see how the stretch happens,
http://www.varmintal.com/a243z.htm
Bingo.
And you discovered the important part. If you are reloading for 9 rifles of the same cartridge,the rifles have tolerances. So,you follow the die mfgr;s instructions. You will get minimal dimension ammo,which will work in all the rifles (probably). But you will also have excessive head clearance with some rifles,and case life will suffer.
OR,you may handload ammo with controlled minimal head clearance for one rifle,and get maximum brass life.
This ability/flexibility is part of what advanced handloading is all about.
You got it!!!
HiBC said:
Actually not a cartoon (artist-drawn animation). Those animations are computer output from a fancy government finite element modeling software package that is actually analyzing the interactions of the material specifications and their properties in response to pressure rises put into the software as arguments. The software output has an option to exaggerate the bends and distortions caused so they are more visible to a human observer. The rainbow colors show the stress locations and degrees calculated by the softward. It's a pretty nifty tool.
Mr T O'Heir
I'm not the police. You can write anything you want.
But please review this thread. Read the posts. See how much dialogue...pleasantdialogue,we have had,and the amount of information that has been exchanged.
And we did it without the same old tired arguments. We are communicating.
Its been nice.
I've been reasonably careful to keep my writing technically correct.Let me know if you have specific complaints.
But what I'm NOT going to do is nit pick somebody else who is making an honest attempt to learn,understand,and contribute.
Once foks understand the concepts,they can fine tune the terminology over time.
If you assign a first grader to write a story about the weekend,and the first grader writes
We wnt tu the crcus and saw a elfunt.
You read it aloud with delight! You went to the circus and saw an elephant.
You let the kid be excited with success!. Communicating. We got his idea!
Let reading and writing be enjoyable.
Don't crush him with phonics,spelling,punctuation,yet. He'll get that...maybe if you just let him enjoy reading books! What better way to learn to spell?
I'm not the police. You can write anything you want.
But please review this thread. Read the posts. See how much dialogue...pleasantdialogue,we have had,and the amount of information that has been exchanged.
And we did it without the same old tired arguments. We are communicating.
Its been nice.
I've been reasonably careful to keep my writing technically correct.Let me know if you have specific complaints.
But what I'm NOT going to do is nit pick somebody else who is making an honest attempt to learn,understand,and contribute.
Once foks understand the concepts,they can fine tune the terminology over time.
If you assign a first grader to write a story about the weekend,and the first grader writes
We wnt tu the crcus and saw a elfunt.
You read it aloud with delight! You went to the circus and saw an elephant.
You let the kid be excited with success!. Communicating. We got his idea!
Let reading and writing be enjoyable.
Don't crush him with phonics,spelling,punctuation,yet. He'll get that...maybe if you just let him enjoy reading books! What better way to learn to spell?
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Yes I do reload for many rifles of the same cartridge ( 4-308's and 7-223/5.56's and no I never follow those die manufacturers instruction . If I want one load to fire in all the rifles I find the one with the largest/longest chamber and size my cases to fit that chamber . This results in the round chambering in all the rifles .
10 of the 11 rifles mentioned have a headspace in between there respective GO & NOGO gauges meaning sizing the cases for the "long" chamber is not creating to much head clearance for the rest . How ever I do have one 308 that has a headspace that barely passes a field gauge . For that rifle it gets it's own custom sized cases for obvious reasons . If not clear why those get custom sized brass . It's because If I were to size them per die manufacture instructions I'd have something like .015+ of head clearance which may very well create a catastrophic failure on the first firing .
Which almost happened the first time I shot it with factory ammo that had .009 of head clearance . With factory ammo my Head to datum measurement grows .010 from factory new to once fired .
That is a bulge in the once fired factory new Winchester ammo . I'll add those cases weigh something like 25gr less then the Federal cases I also shot that day that did not get the same bulge . My thinking is the Winchester ammo has much thinner walls then the Federal cases do .
In closing , no I never adjust my FL sizing dies using the manufacturers instructions . IMO they really should stop using that exact wording . They should explain "why" they recommend that and how it's likely not going to be best for most applications . When I FL size a case per Reddings instructions using there standard FL sizing die and standard shell holder My cases come out .005 shorter from head to datum then my Forster GO gauge . Keeping in mind this is about reloading and that there is only one part of the cartridge that is reloadable . So the die manufacture should keep that in mind for there customers . Very few of us only want one or two loading before we have to scrap are brass . I know I was upset when I learned the instructions are why I only got 3 loadings from that brass and the 200+ pieces left were scrap now because I followed there instructions .
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What should we call the dimension from case head to shoulder reference diameter that's often the same as what's labeled on a headspace gauge for its chamber? Any idea?
Sometimes the same word can be a noun,a verb,or an adjective or adverb.
The noun "Headspace" appropriately applies to the rifle chamber,yes,Mr OHeir,the rifle has a bolt face and a chamber shoulder.
As a verb,the gunsmith or armorer might "headspace" a firearm.
As an adjective,we have a "headspace gauge". No bolt face,no chamber.
But it does have a length between its base and a theoretical datum circle.
No one says "blasphemy" when we call it a headspace gauge.
There is a cartridge case length we have good reason to discuss occasionally.
Without in any way suggesting a cartridge case has "headspace" (noun)
I can suggest,without blaspheme,that the cartridge case length I wish to discuss is the length that is from the case head to a reference datum diameter on the shoulder.
That length fits a chamber in a way similar to a headspace gauge. And really,the point of all this effort is how the cartridge case fits the headspace dimensions of the chamber.
I don't see any reason in the world,besides self-important critics,that we cannot describe a cartridge case length with the word "headspace" as an adjective.
Cartridge length. Which cartridge length? How about the Headspace Cartridge Length,or Cartridge headspace length?
Nothing says the cartridge has headspace .It has a length we can refer to as the length corresponding to the rifle chamber's headspace,and we may transfer measurement off a headspace gauge to ensure the cartridge fits the rifle chamber headspace properly.
"The cartridge length corresponding to headspace"
Or " Cartridge headspace length (headspace as adjective modifying "length")
Or "Headspace cartridge length" (headspace = adjective)
The noun "Headspace" appropriately applies to the rifle chamber,yes,Mr OHeir,the rifle has a bolt face and a chamber shoulder.
As a verb,the gunsmith or armorer might "headspace" a firearm.
As an adjective,we have a "headspace gauge". No bolt face,no chamber.
But it does have a length between its base and a theoretical datum circle.
No one says "blasphemy" when we call it a headspace gauge.
There is a cartridge case length we have good reason to discuss occasionally.
Without in any way suggesting a cartridge case has "headspace" (noun)
I can suggest,without blaspheme,that the cartridge case length I wish to discuss is the length that is from the case head to a reference datum diameter on the shoulder.
That length fits a chamber in a way similar to a headspace gauge. And really,the point of all this effort is how the cartridge case fits the headspace dimensions of the chamber.
I don't see any reason in the world,besides self-important critics,that we cannot describe a cartridge case length with the word "headspace" as an adjective.
Cartridge length. Which cartridge length? How about the Headspace Cartridge Length,or Cartridge headspace length?
Nothing says the cartridge has headspace .It has a length we can refer to as the length corresponding to the rifle chamber's headspace,and we may transfer measurement off a headspace gauge to ensure the cartridge fits the rifle chamber headspace properly.
"The cartridge length corresponding to headspace"
Or " Cartridge headspace length (headspace as adjective modifying "length")
Or "Headspace cartridge length" (headspace = adjective)
To me on all cartridge cases, head to mouth equals case length. Cartridge (overall) length equals head to bullet tip.
Rimless bottleneck cartridge case headspace equals to me, head to shoulder reference. Can be used for rimmed and belted cases that are sized to headspace with their shoulder on the chamber shoulder.
Rimless bottleneck cartridge case headspace equals to me, head to shoulder reference. Can be used for rimmed and belted cases that are sized to headspace with their shoulder on the chamber shoulder.
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I'm good with "Cartridge case headspace length"
I'm just tired of the folkssaying "Cartridges don't have headspace",etc.
Agreed,cartridges do not have headspace. But they do have lengths that we need to communicate about.
If the word "headspace" is used as an adjective to identify the case length we are discussing,then no blasphemy has been spoken,
And the nit picking self righteous critics should,IMO,just shut up and go elsewhere rather than disrupt the discussion.
I'm just tired of the folkssaying "Cartridges don't have headspace",etc.
Agreed,cartridges do not have headspace. But they do have lengths that we need to communicate about.
If the word "headspace" is used as an adjective to identify the case length we are discussing,then no blasphemy has been spoken,
And the nit picking self righteous critics should,IMO,just shut up and go elsewhere rather than disrupt the discussion.
Many are convinced the death knell of neck only resizing fired cases for best accuracy started in the 1950's when Ferris Pindell (one of the "P's" in the PPC cartridge family) convinced Sierra Bullets to full length resize their bottleneck cases used to test their products for accuracy. Bumping the fired case shoulder back. 001" or thereabouts made case necks straightest on cases. As rimless bottleneck case shoulders are well centered on the chamber shoulder when fired, the case neck will center well in the chamber neck without touching it. Bullets are therefore well centered to the bore without touching the bore any place.
Sierra's done that since then. Very popular now with competitive rifle shooters. Several dozen reloads per case is easily attained.
Some reloaders are very competent adjusting their dies in .001 inch increments. They used grade school math to learn twisting the die 10 degrees changed its position .002 inch. Using simple gauges to measure and compare case headspace.
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Don Fischer
New member
Yes I do reload for many rifles of the same cartridge ( 4-308's and 7-223/5.56's and no I never follow those die manufacturers instruction . If I want one load to fire in all the rifles I find the one with the largest/longest chamber and size my cases to fit that chamber . This results in the round chambering in all the rifles .
10 of the 11 rifles mentioned have a headspace in between there respective GO & NOGO gauges meaning sizing the cases for the "long" chamber is not creating to much head clearance for the rest . How ever I do have one 308 that has a headspace that barely passes a field gauge . For that rifle it gets it's own custom sized cases for obvious reasons . If not clear why those get custom sized brass . It's because If I were to size them per die manufacture instructions I'd have something like .015+ of head clearance which may very well create a catastrophic failure on the first firing .
Which almost happened the first time I shot it with factory ammo that had .009 of head clearance . With factory ammo my Head to datum measurement grows .010 from factory new to once fired .
That is a bulge in the once fired factory new Winchester ammo . I'll add those cases weigh something like 25gr less then the Federal cases I also shot that day that did not get the same bulge . My thinking is the Winchester ammo has much thinner walls then the Federal cases do .
In closing , no I never adjust my FL sizing dies using the manufacturers instructions . IMO they really should stop using that exact wording . They should explain "why" they recommend that and how it's likely not going to be best for most applications . When I FL size a case per Reddings instructions using there standard FL sizing die and standard shell holder My cases come out .005 shorter from head to datum then my Forster GO gauge . Keeping in mind this is about reloading and that there is only one part of the cartridge that is reloadable . So the die manufacture should keep that in mind for there customers . Very few of us only want one or two loading before we have to scrap are brass . I know I was upset when I learned the instructions are why I only got 3 loadings from that brass and the 200+ pieces left were scrap now because I followed there instructions .
I'm a lot older than I used to be and my eye's aren't as good. But that does not look like a bulge to me. Look's like where the die quit sizing the case. Every case I size come's out looking pretty much like that. Tward the base of the case, where the mark ends should be the head of the case, solid metal and doesn't expand much with a normal load. Case body expands some and die goes down and put's the body back where it was.
That case was from a factory new Winchester box , there were no sizing die marks on it/them . What you see is a once fired case freshly fired from my rifle and that area is larger then then it's surroundings , It's a bulge .
I wrote on the case because it was one of several I sent to the barrel manufacture showing what there out of spec chamber was doing to new brass . They confirmed the chamber was out of spec and replaced the barrel . Unfortunately the one they sent back was out of spec as well
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