Headspace Comparitor & Bumping

[SheepDog]

LHSmith is right. I have experienced the expansion at the body-shoulder junction when the body was not supported. A once fired brass that was loaded for the same rifle in neck sizing die that pushed the neck shoulder junction and the shoulder just flared out at the junction. It would no longer fit the chamber because the base of the shoulder was too wide. When we form brass from one caliber to another we support the case wall.
The brass is formed under the process of deformation. The brass is simply moved from one place to another along the path of least resistance.

on a side note: the term "headspace" is defined as the length from the datum line of the chamber to the rear of the chamber. (with rimless cases)
With rimmed and belted cases the term is defined as the distance from the step in the chamber to the rear of the chamber. Since a cartridge is not a chamber there is no dimension on it that can be called "headspace". On the SAAMI website you can find the drawings of cartridges with their chamber. Only the chamber has a dimension marked "headspace". the same dimension (taken at the same place) is not even referred to as a reference dimension.

 

[M-61]

Quote from Sheepdog2
...."is defined as the length from the datum line of the chamber to the rear of the chamber..."

I always thought it was datum line to closed face of the bolt.

 

[SheepDog]

If using a bolt action rifle the rear most part of the chamber is the bolt but in a single shot break open rifle there is no bolt but there is a rear of the chamber.

 

[M-61]

If using a bolt action rifle the rear most part of the chamber is the bolt but in a single shot break open rifle there is no bolt but there is a rear of the chamber.

Got it Thanks...I guess I never think beyond a bolt!

 

[fguffey]

dkhunt14 said: ↑
Just because you don't call it headspace, doesn't make it right. The companies and people have been referring to this for many years.

Typing slower: 'IT' has nothing to do with what 'I' call 'IT'; SAAMI says the case does not have head space. SAAMI does not use the head space symbol in case drawings, SAAMI only uses the symbol for head space on the chamber drawing. I do not call a comparator a head space gage.

I understand reloaders are very impressionable, they do not understand the workings of the search engine.

The companies and people have been referring to this for many years.[/

Reeloaders have an infatuation with head space, "Companies and people" understand a reloader would not know what a comparator is so they identify the tool as a 'head space gage', One of the manufacturers of a comparator ask me to agree with him: I would have nothing to do with the arrangement, I suggested reloaders that purchased his comparator thinking it was a head space gage should get their money back. I also suggested any reloader that had a few shop skills could build a comparator and if most of them weren't so hard headed they could use any diameter that was larger in diameter than the case neck and smaller in diameter than case body AND UNDERSTOOD THE DIFFERENCE BETWEEN A HEAD SPACE GAGE AND A COMPARATOR would not need/look up datum diameters if all they were going to do was compare.

Speaking about companies and people; for years and years I have said the Sinclair/Hornady comparator was flawed because their tool use a radius on the hole, I say hole because a datum does not have a radius. I have even made the distinction or difference between the Wilson case gage and the radius on the hole by Hornady. The Wilson case gage 'HAS A RADIUS!' and it works. Problem; I do not believe a reloader has enough ambition to get up/ push away from the key to determine how the Wilson case gage works. I believe that is pathetic; the Wilson case gage has been with us? for 70 years. And Wilson never called it a head space gage, I make chamber gages, I check my chamber gages with a head space gage and I can verify my case gages with a head space gage.

I have no ideal what reloaders use because to a reloader everything is a head space gage and everything has head space.

F. Guffey

 

[Eddie Harren]

"I have no ideal what reloaders use because to a reloader everything is a head space gage and everything has head space."

There is certainly no shortage of headspace in this statement!

 

[fguffey]

This is why we bump shoulders and measure cases

You assume the shoulder moves when you 'bump' it.. The first person does not have a chances when he claims he has been reloading for 30 years, if there is any truth in the claim I would have to say some people can be around something all their life's and know nothing about it. Back to 'you assume'; in the beginning it was not the shoulder that bumped, it was the press. In the beginning there were two types of presses, one was cam over press. The cam over press was called a 'bump press'. And then there was the other press, the non-cam over press; the non cam over press did not bump.

The RCBS A2 was a cam over press, it was a bump press, I could ask how much bump did the A2 have but first I would have to explain what 'bump' means. I have 3 Rock Chuckers, none of my Rock Chuckers cam over meaning they are not bump presses. And then reloaders call RCBS and explain to them what this mean old man said about the Rock Chucker. I have at least 12 presses that are bump presses, by design the bump was necessary for two reasons.

And then there were instructions, I have two sets from RCBS, one set describes the cam over press and die adjustment, the other describes die adjustment for the non cam over press. What was the difference?

F. Guffey

 

[LHSmith]

Typing slower: 'IT' has nothing to do with what 'I' call 'IT'; SAAMI says the case does not have head space. SAAMI does not use the head space symbol in case drawings, SAAMI only uses the symbol for head space on the chamber drawing. I do not call a comparator a head space gage.

I understand reloaders are very impressionable, they do not understand the workings of the search engine.



Reeloaders have an infatuation with head space, "Companies and people" understand a reloader would not know what a comparator is so they identify the tool as a 'head space gage', One of the manufacturers of a comparator ask me to agree with him: I would have nothing to do with the arrangement, I suggested reloaders that purchased his comparator thinking it was a head space gage should get their money back. I also suggested any reloader that had a few shop skills could build a comparator and if most of them weren't so hard headed they could use any diameter that was larger in diameter than the case neck and smaller in diameter than case body AND UNDERSTOOD THE DIFFERENCE BETWEEN A HEAD SPACE GAGE AND A COMPARATOR would not need/look up datum diameters if all they were going to do was compare.

Speaking about companies and people; for years and years I have said the Sinclair/Hornady comparator was flawed because their tool use a radius on the hole, I say hole because a datum does not have a radius. I have even made the distinction or difference between the Wilson case gage and the radius on the hole by Hornady. The Wilson case gage 'HAS A RADIUS!' and it works. Problem; I do not believe a reloader has enough ambition to get up/ push away from the key to determine how the Wilson case gage works. I believe that is pathetic; the Wilson case gage has been with us? for 70 years. And Wilson never called it a head space gage, I make chamber gages, I check my chamber gages with a head space gage and I can verify my case gages with a head space gage.

I have no ideal what reloaders use because to a reloader everything is a head space gage and everything has head space.

F. Guffey

To get the full potential of the Wilson Case Gage, you will need to purchase a depth Mic ~$ 150 + the cost of the case gauge ~ $29 (which is cartridge specific) . A Hornady cartridge"headspace" comparitor will cost ~ $40 which will allow you to determine shoulder set-back (bump) on multiple cartridge cases and a 0-6" caliper ~ $30.
No matter which tool, each chamber will have it's own unique end of chamber to shoulder datum length which should be with-in SAAMI ( or with in allowances of the go and no go gages supplied with custom reamers). Every reloader should determine and record this dimension, and set their dies accordingly rather than the default die adjustment stated in the die instruction sheet.
I will cede Guffy's point on use of case gage if the chamber in question was never confirmed to pass the go/ no go. However, many of this sites readers shoot competition where "Extreme Rifle Accuracy" is demanded and those reloading techniques differ vastly from old school military rifle jargon and methods. Many other readers come here to get tips on how to accurize their varmint or non-comp target rifles.
Arguing over semantics only confuses the process to those looking to learn. If RCBS or Hornady (both members of SAAMI) want to name a product that best describes it's intended use, and has been labeled as such for years without any legal issues the argument becomes silly and counter-productive.

 

[LHSmith]

.

I have no ideal what reloaders use

F. Guffey

^^^^^There-in lies the crux of the problem. New reloading methods/ tooling have advanced rifle accuracy "light years" ahead of the old days, all the while doing it safely while often pushing the edge.

 

[fguffey]

I also suggested any reloader that had a few shop skills could build a comparator and if most of them weren't so hard headed they could use any diameter that was larger in diameter than the case neck and smaller in diameter than case body AND UNDERSTOOD THE DIFFERENCE BETWEEN A HEAD SPACE GAGE AND A COMPARATOR would not need/look up datum diameters if all they were going to do was compare.

And then there is R. Lee; he wrote a book about modern reloading. R. Lee is the only company that furnished information for the case datum on case drawings. He includes the diameter of the hole; again, when using a comparator it is not necessary to use the correct diameter datum. Again, I make datums, I collect datums and I have purchased datums. I was at a gun show when I noticed a box on a dealers table; I said "DATUMS!". Standing next to me were three reloaders; one ask me, "What does a datum look like?", another ask, "WHERE?" and the dealer said he did not have no datums.

F. Guffey

 

[John Russell]

You assume the shoulder moves when you 'bump' it.. The first person does not have a chances when he claims he has been reloading for 30 years, if there is any truth in the claim I would have to say some people can be around something all their life's and know nothing about it. Back to 'you assume'; in the beginning it was not the shoulder that bumped, it was the press. In the beginning there were two types of presses, one was cam over press. The cam over press was called a 'bump press'. And then there was the other press, the non-cam over press; the non cam over press did not bump.

The RCBS A2 was a cam over press, it was a bump press, I could ask how much bump did the A2 have but first I would have to explain what 'bump' means. I have 3 Rock Chuckers, none of my Rock Chuckers cam over meaning they are not bump presses. And then reloaders call RCBS and explain to them what this mean old man said about the Rock Chucker. I have at least 12 presses that are bump presses, by design the bump was necessary for two reasons.

And then there were instructions, I have two sets from RCBS, one set describes the cam over press and die adjustment, the other describes die adjustment for the non cam over press. What was the difference?

F. Guffey

Frank, Dude - you gotta get your facts straight !!!

Cam-over, and Bump have nothing to do with each other.

On "Cam-over"...

"C-frame" presses. The C-frame press is an early part of reloading history. They were flexible and sprung like a rubber ducky. But in the early days, the need for a loading press was only to save money loading - no one formed cases or wildcats with C-frame presses. "Wildcats" were NOT made by pushing and squishing shoulders around in a press, they were formed by blowing out shoulders in the chamber - the AI case.

The C-frame, like slavery and the Indian massacres, was a dark period in American reloading history, and is best forgotten.

In 1949, the C-frame died. In 1949, Fred Huntington freed us from that darkness by inventing the model "A" press - it was the very first "O-frame" press. It was designed for reloading, AND bullet swaging, because most varmint and accuracy shooters in those days, made their own bullets. He was smart and patented the design, and made O-frame presses (and royalties from all the other press manufacturers), and great dies, and lived happily ever after.

All "O" frame presses that I have used, owned, or visited at a friends are "Cam over", and this goes back to the original "A" and "A2". Cam over means that the linkage that drives the ram, first makes the ram go up to the top of the stroke, and then goes a bit further, so the ram starts going down again - then the linkage hits a stop. ALL "O" frame presses do this - it is inherent in the design.

RCBS, CH, Redding, Lyman, Hornady, and the rest, have never made an O-frame press that is not capable of "camming-over". If you have RockChucker presses that are not capable of cam-over, they have been modified (to their detriment)... or maybe you just don't understand how to use that feature.

When you set up dies, and screw a sizing die down to meet the ram and lock it in place, you are not using the cam-over feature. When you full length size a case, the case will cause the O-frame to flex, so the case will not go all the way in. SO... we use the cam-over abilities fof the press, by when the die is screwed down to meet the ram, we lower the ram and screw the die in further by 1/8th to maybe 1/2 a turn, and lock it in place.

Now, when we run the press handle down (and the ram goes up), we hit the die and feel resistance - as we continue, the O-frame starts to stretch up, and as the linkage goes over "top-dead-center", the handle continues down on it's own force as the O-frame stretch starts to unload it's stress back into the ram and linkage.

At the bottom of the stroke, the press will remain lightly locked in place. This ability to cam-over assures that the case will be completely sized, even when the frame flexes a bit.

THAT, Frank, is "Cam-over"... you have it, even if you are not using it.

---

On "Bumping"...

"The RCBS A2 was a cam over press, it was a bump press,...".

Bumping is NOT a feature of presses, ANY presses. It is done by the dies. And it could never be attributed to the "A" and A2" presses (or any other press - for that matter, you could bump with an old C-frame press).

"Bumping" is a newish word in the handloading lexicon. I think it started showing up maybe 8 to 10-ish years ago. It originally meant to just nudge the shoulder - like you might "bump" someone's car in the parking lot, as opposed to damaging it.

Like a lot of misused words in handloading, it has morphed to now mean anything that has to do with sizing the shoulder. So when a newbee takes his oversize and overly long case from his $300 Savage factory chamber, and shoves it into a SAAMI minimum FL sizing die, he thinks (and says) that he is "bumping" the shoulder." (Gag... double Gag)

None the less - bumping, for experienced shooters means just nudging the shoulder 1 or 2 or 3 thou, and you control the amount by how much you screw in the bump die... or you can control the amount by using Redding Comp shell holders (which is how I do it).

So, Frank - we all know that you have some very strange opinions on reloading, but could do us a favor and at least use the same language as the rest of the world... in the cause of better communication.

 

[Eddie Harren]

And then there is R. Lee; he wrote a book about modern reloading. R. Lee is the only company that furnished information for the case datum on case drawings. He includes the diameter of the hole; again, when using a comparator it is not necessary to use the correct diameter datum. Again, I make datums, I collect datums and I have purchased datums. I was at a gun show when I noticed a box on a dealers table; I said "DATUMS!". Standing next to me were three reloaders; one ask me, "What does a datum look like?", another ask, "WHERE?" and the dealer said he did not have no datums.

F. Guffey

WTH are you talking about? I need the translator up here now!

 

[RonAKA]

I agree the term "headspace" is confusing. I appreciate that it is "formally" described as the distance from the bolt face or datum line to the shoulder. However, the term itself implies you are measuring a gap or space. And at the end of the day that gap or space is the critical measure for the reloader. Basically there is a useage for headspace for the gunsmith or owner setting up a barrel on the action, and another use of the term headSPACE, for the reloader.

As for the types of press used, cam over or solid stop, I don't see the relevance. I own one of each. They both can do the same job of bumping a shoulder. The rubber hits the road, so to speak when the sizing die hits the shell holder. It is the shell holder/die combination that determines what you can do with the case, not the press.

I think one of the issues in reloading that is not fully understood is that the distance from the base level in the shell holder to the face of the shell holder is critical. I think there is a supposed standard dimension of 0.125". However two I have (Lyman, and no name, Lee?) measure closer to 0.123". They have 0.002 more bump potential built in than a so called standard. Then there is the die issue. Is it made for a 0.125 or a 0.123" or what? RCBS according to their product description claim they size the body of a case to minimum SAAMI, but the shoulder to maximum SAAMI. If you combine a RCBS die built like that, with a fat shell holder, you may not be be able to bump to even maximum SAAMI.

Bottom line is that after the gun is bought or built, a reloader needs a method to measure the SPACE that a sized cartridge has at the shoulder, regardless of what you want to call it. And you need a shell holder that is skinny enough to get the shoulder bump done.

 

[JRS]

Frank, Dude - you gotta get your facts straight !!!

Cam-over, and Bump have nothing to do with each other.

On "Cam-over"...

"C-frame" presses. The C-frame press is an early part of reloading history. They were flexible and sprung like a rubber ducky. But in the early days, the need for a loading press was only to save money loading - no one formed cases or wildcats with C-frame presses. "Wildcats" were NOT made by pushing and squishing shoulders around in a press, they were formed by blowing out shoulders in the chamber - the AI case.

The C-frame, like slavery and the Indian massacres, was a dark period in American reloading history, and is best forgotten.

In 1949, the C-frame died. In 1949, Fred Huntington freed us from that darkness by inventing the model "A" press - it was the very first "O-frame" press. It was designed for reloading, AND bullet swaging, because most varmint and accuracy shooters in those days, made their own bullets. He was smart and patented the design, and made O-frame presses (and royalties from all the other press manufacturers), and great dies, and lived happily ever after.

All "O" frame presses that I have used, owned, or visited at a friends are "Cam over", and this goes back to the original "A" and "A2". Cam over means that the linkage that drives the ram, first makes the ram go up to the top of the stroke, and then goes a bit further, so the ram starts going down again - then the linkage hits a stop. ALL "O" frame presses do this - it is inherent in the design.

RCBS, CH, Redding, Lyman, Hornady, and the rest, have never made an O-frame press that is not capable of "camming-over". If you have RockChucker presses that are not capable of cam-over, they have been modified (to their detriment)... or maybe you just don't understand how to use that feature.

When you set up dies, and screw a sizing die down to meet the ram and lock it in place, you are not using the cam-over feature. When you full length size a case, the case will cause the O-frame to flex, so the case will not go all the way in. SO... we use the cam-over abilities fof the press, by when the die is screwed down to meet the ram, we lower the ram and screw the die in further by 1/8th to maybe 1/2 a turn, and lock it in place.

Now, when we run the press handle down (and the ram goes up), we hit the die and feel resistance - as we continue, the O-frame starts to stretch up, and as the linkage goes over "top-dead-center", the handle continues down on it's own force as the O-frame stretch starts to unload it's stress back into the ram and linkage.

At the bottom of the stroke, the press will remain lightly locked in place. This ability to cam-over assures that the case will be completely sized, even when the frame flexes a bit.

THAT, Frank, is "Cam-over"... you have it, even if you are not using it.

---

On "Bumping"...

"The RCBS A2 was a cam over press, it was a bump press,...".

Bumping is NOT a feature of presses, ANY presses. It is done by the dies. And it could never be attributed to the "A" and A2" presses (or any other press - for that matter, you could bump with an old C-frame press).

"Bumping" is a newish word in the handloading lexicon. I think it started showing up maybe 8 to 10-ish years ago. It originally meant to just nudge the shoulder - like you might "bump" someone's car in the parking lot, as opposed to damaging it.

Like a lot of misused words in handloading, it has morphed to now mean anything that has to do with sizing the shoulder. So when a newbee takes his oversize and overly long case from his $300 Savage factory chamber, and shoves it into a SAAMI minimum FL sizing die, he thinks (and says) that he is "bumping" the shoulder." (Gag... double Gag)

None the less - bumping, for experienced shooters means just nudging the shoulder 1 or 2 or 3 thou, and you control the amount by how much you screw in the bump die... or you can control the amount by using Redding Comp shell holders (which is how I do it).

So, Frank - we all know that you have some very strange opinions on reloading, but could do us a favor and at least use the same language as the rest of the world... in the cause of better communication.

Nils Kvale (NORMA) designed the first C frame reloading press, dies and other reloading tools, and at some point when NORMA could no longer keep up with demand, entered into an agreement with Fred Huntington to sell their line of reloading tools. The rest is history.

Edit: The Lee Classic Cast does not have a "cam over" feature.

 

[M-61]

fguffey said:
Typing slower: 'IT' has nothing to do with what 'I' call 'IT'; SAAMI says the case does not have head space. SAAMI does not use the head space symbol in case drawings, SAAMI only uses the symbol for head space on the chamber drawing. I do not call a comparator a head space gage......"

Not to confuse matters even more (possible?) but I doubt that SAAMI said 'a case does not have head-space'. Why would they make that statement? It is irrelevant.
Now what I think you are saying (in nearly every post) '...my cases don't have head-space...' well that is true but also since you end it there it becomes confusing. Why? Where then IS the head-space? Well it is in the action of the rifle. YOUR fired cases (as well as everyone else) are a result of whatever that head-space in your action was set to.
Bottom line: stating your cases lack head-space is confusing if you end the statement there and at least to me makes it sound as if some back woods gypsy mysticism is involved that only you know about.

 

[fguffey]

I agree the term "headspace" is confusing. I appreciate that it is "formally" described as the distance from the bolt face or datum line to the shoulder.

Not quite: The length of the chamber is measured from the datum to the bolt face or from the shoulder of the chamber to the bolt face. And then again the case does not have head space but the difference in length between the chamber from the shoulder to the bolt face and the case from the shoulder of the case to the case head is clearance. And SAAMI said; "reloaders are confused" even thought they make it very clear in their definitions of terms. Anyhow; that is the reason I off set the length of the chamber with the length of the case; and I understand that is so confusing to a reloader.

F. Guffey

 

[dmoran]

...... And SAAMI said; "reloaders are confused" .......
F. Guffey

​

​

 

[RonAKA]

Not quite: The length of the chamber is measured from the datum to the bolt face or from the shoulder of the chamber to the bolt face. And then again the case does not have head space but the difference in length between the chamber from the shoulder to the bolt face and the case from the shoulder of the case to the case head is clearance. And SAAMI said; "reloaders are confused" even thought they make it very clear in their definitions of terms. Anyhow; that is the reason I off set the length of the chamber with the length of the case; and I understand that is so confusing to a reloader.

F. Guffey

Sorry, but I have no idea what your point is, and I'm not confused.

 

[fguffey]

I agree the term "headspace" is confusing. I appreciate that it is "formally" described as the distance from the bolt face or datum line to the shoulder

line to the shoulder

That is where reloaders started, they thought there was a line on the shoulder, there was no line and there was no arrow pointing to the line identifying the line as a datum. Some reloaders continue to call the line 'the datum line'. There is no line, there is a circle/hole, most of my datums measure .375" and .400" in diameter but when using a comparator the diameter is not important.

It is not easy to find a place on the shoulder with a line.

F. Guffey

 

[fguffey]

And for years reloaders thought the datum was halfway between the shoulder/neck juncture and the case body/shoulder juncture, and I always ask; "How can that be if the datum is the same for the 8mm57, 30/06, 280 Remington, 270 Winchester and the 25/06? If the datum is .375" in diameter how can the datum be half way between the two junctures on all 5 cases? Meaning to be half way on all 5 cases all of the datums would have to be different diameters.

F. Guffey