Dies for Bumping Shoulder

[Bart B.]

Every new case I've fired has that "pressure ring" that measured some thousandths bigger after firing than before. Full length sizing reduces its diameter a little but never back to that of unfired diameter.

Use a micrometer to measure a few new cases then again after firing then again after full length sizing.

 

[Metal god]

Every new case I've fired has that "pressure ring" that measured some thousandths bigger after firing than before.

None of mine do . Oh I sometimes see something but that's often where the case transitions from supported to unsupported in the chamber . There is markings but never a bulge . But lets say you're correct and every case I fire should have that mark and bulge . Then why didn't the Federal cases I shot the same day from the same rifle only seconds later have those same marks and bulge ? You did say EVERY new case you have fired has those marks correct ? I must be pretty darn special then .

 

[Bart B.]

Then why didn't the Federal cases I shot the same day from the same rifle only seconds later have those same marks and bulge?

Greatly reduced loads? Extremely smooth chamber wall?

Did you mic them before and after firing?

 

[Metal god]

see below

Greatly reduced loads? Not likely

Extremely smooth chamber wall?
absolutely not which was another reason I sent the barrel back . Major tooling marks showing up on my fired cases .

Did you mic them before and after firing?
Not before , didn't realize the importance of that until after and had fired all 40 rds I had

 

[Bart B.]

Use a hole micrometer or pin gauges to measure the chamber diameters in that area. If they're close enough to new case diameters, no bulge can be normal.

There's only .0013" difference between SAAMI spec maximum case and minimum chamber diameters in the pressure ring area. Some chamber reamers are smaller and virtually equal to new cases at that point.

 

[RC20]

To me on all cartridge cases, head to mouth equals case length. Cartridge (overall) length equals head to bullet tip.

Agreed.

For whatever it worthy to anyone:

I think the term resize suits the operation in discussion.

You can do a minimum resize or bump, whatever term appeals to you or as far as I am concerned you can use head space but you need to sub phrase it to be clear.

A fired case is in essence a very low quality head space gauge (on a Savage you can use it for that purpsoe and some do.)

But we really are not head spacing anything, we are just sizing. It may be as little as we can quality control for or the major die mfg recommend full tilt shoulder push back (CoAx aside)

Understanding Head space is useful for a mental picture (or a physical drawing) of understanding what a cartridge does and should do in a chamber (and should not do)

But we don't use a head space gauge which is a .001 device (maybe a bit better) we use a micrometer and a comparitor on the shoulder so assess if we are getting what we want. If we get that minimum bump back we also get the sizing we need on the rest of the case.

So, I go with Shoulder Bump Back or Minimum resizing if that is my goal with the case. shoulder.

And the nit picking self righteous critics should,IMO,just shut up and go elsewhere rather than disrupt the discussion.

What is funny is to have people talk about this in terms that makes it the end of the world. This is a gun chamber for crying out loud.

I have re-built and worked on a lot of engines. All our work had tolerance and a lot of it (maybe all) had wider tolerance than .001 disused here.

Con Bearing gap? (.0025 is a good average)

Shaft end play: Easily .005, some are more.

The only area I knew worked in .0001 was diesel fuel injection components.

I replaced a lot of those parts, but I sure never worked on em. Bench work only with some really good equipment.

 

[HiBC]

I've seen that "bulge",or,more accurately,"step" on cartridge cases.

I'd just chambered a 30-06 AI,I used a new Elliot or PTG reamer,and I had just added a floating reamer holder to my tools.

Test fired the rifle and saw the step. I was concerned.Did I scrape the chamber bell mouth somehow?

Using pin gauges to measure the chamber mouth,and mic ing the reamer flutes,My chamber was cut precisely to size.,and checking the drawing,the reamer was correct.It was not a chamber problem.

The actual problem was the factory new brass was running about .005 undersize on the diameter.

There is more than one way to get a step.

 

[Bart B.]

One good thing the pressure ring shows is case wall thickness uniformity. If the step is the same height all the way around, case wall thickness is very uniform all the way around. If not, the high point indicates the thicker wall part.

 

[jetinteriorguy]

@ Metalgod, don't you mean to say you size all your rounds to fit the shortest chamber, not the longest one? If you size for the longest one it won't fit in the shorter chamber.

 

[Metal god]

@ Metalgod, don't you mean to say you size all your rounds to fit the shortest chamber, not the longest one?

Yep , thank you for the correction . Now if I could just find the FACEPLANT emoji haha .

 

[reynolds357]

Bumping the shoulder huh? Don't suppose you can define just what bumping the shoulder means? You size the shoulder and you size the whole case equally! I like to use the term partial sizing but even that is wrong. You can't partially size a case with an FL dies unless you size only the neck! Once you have moved the shoulder at all you have actually full length sized the case. Bumping the shoulder or partial sizing it actually full length sizing to fit the chamber the case is fired in and maybe not any other. FL sizing dies come from the factory with instructions to set them up so that the ammo wll fit in any chamber. Then the OLL in the reloading manual is suggested so the loaded round will fit in any magazine for that cartridge. Depending on your rifle, you can adjust how much you full length the case in sizing, how much I don't know foe sure but any where from SAMMI min to SAMMI max! All instructions are for SAMMI min so they will fit every chamber without the case being overly worked on firing. OLL is set to match the length so that the round will fit in all magazine's and not touch the lands when laded that way. Full length sizing the best way, IMO, can make your case fit any chamber to one that is actually an over head space chamber. Take a case from a rifle with excessive headspace and neck size only till the action will no longer close on the case and then adjust the die to size the case till the bolt will close on it and you have FL size the case to that chamber. If you size a case for a chamber like that to min SAMMI spec's as they instruction's say to do, three or four shot's down the road you will likely separate the case at the head!

I think the term, bump the shoulder came about as a term for moving the shoulder just enough to allow the case to fit that certain chamber. I have two 243's, never had two of anything before. Each one has it's own set of dies set to FL size the case to that rifle. Ammo from one set of die's will fit in booth rifle's but from the other set, only one rifle, in the other the bolt won't close. In both case's the the case is full length sized for the particular rifle and I don't believe either is over SAMMI max spec.

All the above is assuming you are using a standard full length die. On my 1000 yd rifles, I use neck sizing die, body die, and shoulder die. I can "bump" or severely set back a shoulder without doing anything to the rest of the case.

 

[pwc]

Case length= case head to mouth controlled by the “trim to” length.

Cartridge length (COAL) = case head to bullet tip. Will be different for different bullets and seating depth and is needed to ensure a cartridge will fit in a given magazine.

Case head to datum= case to barrel fit set by gauges during the manufacturers barrel chambering. Referenced to the SAAMI standards.

Headspace = the distance between the case head and the bolt.
A discussion of headspace without reference to the bolt is meaningless. Without the bolt there can be no headspace. A given barrel in two different actions can have different headspaces. A properly sized case that matches the Go gauge for a specific barrel will still have headspace when introduced into that barrels action.
The reloaders job then, is to determine what that distance is from the bolt face to the back of the case head and minimize it to keep the case from stretching which leads to head separation.

Case head to datum is a more arbitrary length for the reloader when seeking to “bump” the case shoulder to allow for their desired case expansion during firing. This dimension is determined by the reloader’s sizing procedure and it will affect the headspace, but it is NOT headspace.

 

[Bart B.]

Case head to datum= case to barrel fit set by gauges during the manufacturers barrel chambering. Referenced to the SAAMI standards.

Headspace = the distance between the case head and the bolt.

SAAMI's glossary says the distance between the case head and the bolt face is head clearance. They say it's commonly confused with head space. And headspace is the distance from the face of the bolt to the surface in the chamber on which the cartridge case seats.

https://saami.org/saami-glossary/

The reason rimless bottleneck case's (functionally headspacing on the chamber shoulder) head to shoulder reference is commonly called head space is because their chamber head space gauges have near identical dimensions from their head to their shoulder reference. The difference between case headspace and chamber headspace equals head clearance.

Ditto for belted and rimmed bottleneck cases resized to headspace on their chamber shoulder.

If the measurement from case head to shoulder was called "breeching" space, it would relate well to "breeching plug;" another SAAMI term for headspace gauge.

 

[Unclenick]

No one says "blasphemy" when we call it a headspace gauge.

That name is accurate because it refers to a gauge designed to measure chamber headspace indirectly. It measures chamber headspace by making what is called a transfer measurement taken off a case fireformed to fill out to the size of that chambaer. If you read the RCBS PM instructions, it describes determining headspace by measuring a fireformed case. But when you measure a resized case, you are not determining headspace because that case is no longer the size of the chamber.

I'm just tired of the folkssaying "Cartridges don't have headspace",etc.

Headspace is the space a case head fits into (or a head and belt or a head and shoulder or a head and case mouth). As far as I know, commercially, the only company in the business to embrace the use of "headspace" as a case dimension, regardless of how it fits in any chamber, is Hornady. The nonsensical aspect is that a head doesn't have to fit inside a case so it doesn't need any headspace in it. What a case does have is a headspace-filling exterior dimension made up of matter (not space) that partially or fully occupies a chamber's headspace depending on how it has been handled. If you want to call that headspace-filling dimension 'case headspace', I don't really mind. My only concern is when people want to know what actual headspace is that they not be misled by the term being used to mean two different things: the size of an empty space and the size of something that typically fills that space only partway. Where both terms appear, that usage distinction has to be deduced from the context, making the meaning of "headspace" implicit rather than explicit. That means more effort is needed to accurately follow the discussion. I don't suppose most people have very much trouble following it, but newbies may, if anybody does. I blame that on Hornady.


Head clearance is not headspace. It is the excess headspace in front of the breech face when the cartridge case is fully forward against its seating surface in the chamber.

 

[Bart B.]

Redding also supports the idea that headspace is the space behind the case head to the bolt face.

They also support the idea that cartridges can lay in the chamber bottom when fired.

And it's ok if the bolt binds up a little chambering a round.

Read all about it in....

https://www.redding-reloading.com/tech-line-a-tips-faqs/145-dealing-with-headspace

....where they ignore (if they're aware of):

* how a strong spring loaded firing pin (and spring loaded ejector) moves the chambered cartridge before it fires.

* why accuracy suffers when bolts bind chambering cartridges.

 

[Unclenick]

Yeah, that's like with Hornady and case headspace. I'll guess both were probably driven by one person who uses the term that way and convincing others it is the way to go. I would say SAAMI needs to field some proof-readers, but compliance is voluntary, so they won't.

 

[HiBC]

Quote:
Originally Posted by HiBC
No one says "blasphemy" when we call it a headspace gauge.
That name is accurate because it refers to a gauge designed to measure chamber headspace indirectly. It measures chamber headspace by making what is called a transfer measurement taken off a case fireformed to fill out to the size of that chambaer. If you read the RCBS PM instructions, it describes determining headspace by measuring a fireformed case. But when you measure a resized case, you are not determining headspace because that case is no longer the size of the chamber.

Quote:
Originally Posted by HiBC
I'm just tired of the folkssaying "Cartridges don't have headspace",etc.
Headspace is the space a case head fits into (or a head and belt or a head and shoulder or a head and case mouth). As far as I know, commercially, the only company in the business to embrace the use of "headspace" as a case dimension, regardless of how it fits in any chamber, is Hornady. The nonsensical aspect is that a head doesn't have to fit inside a case so it doesn't need any headspace in it. What a case does have is a headspace-filling exterior dimension made up of matter (not space) that partially or fully occupies a chamber's headspace depending on how it has been handled. If you want to call that headspace-filling dimension 'case headspace', I don't really mind. My only concern is when people want to know what actual headspace is that they not be misled by the term being used to mean two different things: the size of an empty space and the size of something that typically fills that space only partway. Where both terms appear, that usage distinction has to be deduced from the context, making the meaning of "headspace" implicit rather than explicit. That means more effort is needed to accurately follow the discussion. I don't suppose most people have very much trouble following it, but newbies may, if anybody does. I blame that on Hornady.


Head clearance is not headspace. It is the excess headspace in front of the breech face when the cartridge case is fully forward against its seating surface in the chamber.

Unclenick: You know I have great respect for your knowledge and point of view.

I'll say it once more,then let it go. It seems a waste of time to do so,as I have not seen any response from anyone that indicates they understand what I'm saying.

That probably means my idea is not useful. I'm not the guy who says :"I'm the only reloader…" When "I'm the only" I might be wrong.

Once again,I agree that cartridges do not have headspace This is using the word "Headspace" as a noun.

But the headspace gauge does not have headspace either. The word "headspace" is appropriately used as an adjective to describe the use of the gauge .

Using the same logic,I adamantly do not use the term "headspace" applied to a cartridge case when the word "headspace" is used as a noun.

But a cartridge case does have measurable dimensions. Diameters,angles,lengths.

We can measure rim diameter,call it rim diameter,and communicate. We can talk about case head diameter before and after firing and come up with case head expansion. When I say "head diameter,you know which diameter I'm talking about.


Without saying a case has headspace,I can describe the length of a cartridge case from case head to shoulder reference diameter as "The cartridge case length that we associate with the headspace of the rifle"

I can identify "Which length?" by using the word "Headspace" as an adjective to identify a measurable length in the same way I can use the word "Headspace" as an adjective to identify a gauge.The cartridge case DOES have that length. The argument is over what to call that length when we measure the cartridge case.

No one has provided a useful accepted term. To fill the void,I have provided "Cartridge case length (the noun) modified by the adjective "Headspace"


I also fully understand the term "Head Clearance" I use it. Very often it is the useful term.

Now,I think I will go back to being retired from discussing this topic.

I'm the only one who can choose to stop pounding my head against an anvil.

 

[Bart B.]

HiBC, how about case "body length" or "body space?"

 

[HiBC]

I'd be happy with any term we can agree on.
I'd be happy with any term I can use to help a beginner understand the process of setting up dies to a specified minimum head clearance.

I'd be happy with any term that facilitates transitioning a discussion from understanding headspace in the rifle chamber to understanding setting up reloading dies for a specific head clearance.

I want a teaching and communication tool.

I don't have an ego need for it to be the words I choose. For some reason we write a lot because we don't have a term.

I just stepped up and tried to provide one. I gave my reasons why.

If anybody has a better term,by all means! Lets just get this over with.

The thing seems to be,if any of us proposs an idea,its like launching a clay pigeon in front of a Firing Line Forum.

It has toget blasted out of the sky.

But none of the acknowledged experts will step up with a term we can use.

I'd appreciate it if you could train me how to use "body length" to teach a new reloader about setting dies for desired head clearance without using the word "headspace"

I'd be very happy to learn. The anvil is bloody and my head hurts.

 

[pwc]

This thread reminds me of a similar discussion about cycles and Hertz.

Heinrich Hertz is the guy that discovered the cyclic nature of AC. one positive excursion followed by one negative excursion in a sinusodial wave = 1 cycle. A measurement that has a useful finite meaning.

In the late '60s, someone decided poor Heinrich didn't get the recognition he deserved (probably some liberal) and started a campaign to change cycle to Hertz. Well, they were successful...that's why you zee old radio dials with the frequency in kilocycles (Kc) and new frequency measurements in Hertz (KHz)

Now all this thread discussion is about keeping our brass from stretching just in front of the case head. Caused by the brass moving back to contact the bolt face. Usually ma.nifested by a bright ring around the case.

Others here have been reloading longer than me (35 yrs), but from my beginning, the above condition was stated to be caused by "excessive headspace", the movement of the case head back against the bolt face. That distance between the bolt and case head IS headspace.

Now that description is understandable and has specific meaning. So, this thread can continue to explore freshman Enhlish 101.....for me, I'm going to use the term that most folks understood from the time I began reloading....I'm not going to move from a meaningful name/description like cycle or hesdspace to something abstract as Hz or ????