Shoulder bump Part 2

[7887mm08]

So awhile back I posted how when checking shoulder bump for a 222 that my once fired cases were .014" longer than new brass, and it generated response. Well now I am setting up dies to load for a 243. I checked about 20 once fired cases and all were within .001" I wrote that measurement down and I subtracted .002" (for shoulder bump). Well again I checked the last remaining new Winchester brass that I had on hand to see how much my cases were growing. Guess what THE MEASUREMENT IS THE SAME! Cases didn't grow. Now I am really confused. When I first reloaded this new brass I did not re-size it I am thinking I must have a minimum chamber The bolt closed with ease when chambering. To ad a little more to the story, I received about 300 range pickup 243 brass recently, I tumbled these and deprimed for future use. I thought I would measure the shoulders on a few of these. I pulled out 20 and measured them guess what SAME EXACT SIZE AS MY ONCE FIRED AND NEW BRASS! What am I to think of this? I think my 20 degree shoulder bump insert is bad What do you all think?

 

[Dusty Stevens]

Its a piece of metal attached to calipers. How could it be bad?

 

[7887mm08]

If they cut the angle to large of a diameter then I think it may be locating off of the corner of the shoulder and not the flats of the shoulder. IDK that's why I am asking for help Seems strange but possible that brass fired from at least two different guns has the Exact same measurement as new brass.

 

[fguffey]

What am I to think of this? I think my 20 degree shoulder bump insert is bad What do you all think?

I do not have these problems, I make gages, and my gages are not case friendly. I have case gages and I have comparators. It would help you if you understood how a datum is used. My datum references do not distinguish the difference between shoulder angles.


F. Guffey

 

['Freak]

If you ordered and they sent the correct 20° bump gauge insert, #749-011-477 per catalog 2015-B, for the 308 Winchester family of cartridges, then the insert alone is not to blame.

 

[ireload2]

Maybe you should write your .243 observations in list form. Then you can refer back to a previous list number.
Right now it is not clear what is the same
You checked the last new Winchester brass? Checked it before or after it had been fired? Or both?

Do you use the same ZERO for your calipers each time?

 

[7887mm08]

Maybe you should write your .243 observations in list form. Then you can refer back to a previous list number.
Right now it is not clear what is the same
You checked the last new Winchester brass? Checked it before or after it had been fired? Or both?

Do you use the same ZERO for your calipers each time?

Both new and once fired measure the same. all measurements are the same. I don't now how to say it any more clear

 

[ireload2]

One of the problems with the bump gauges is if they are not zeroed to a headspace gauge is you still don't know if the brass is long, the chamber is short or it is a combination of both the chamber and brass approaching zero clearance.

This zero clearance is approached as both the case and the chamber approach what is called maximum material condition.
Maximum material on the case is a max length case and maximum material in the chamber is the minimum length chamber.
SAAMI cases and chambers are usually designed to permit a maximum length case fit into a minimum length chamber.
But not always. There are some cases that can meet the SAAMI drawing yet not fit the SAAMI chamber. This issue is not limited to SAAMI. There are also CIP standards that permit a case too long for the chamber.
This is called the Delta L problem and it is discussed here. The 30-06 is one of those rounds with the Delta L problem.
https://en.wikipedia.org/wiki/Delta_L_problem

In your case you don't know if you have long brass or a short chamber. Based on the evidence of range brass that measured the same I would expect you have a normal chamber and your NEW brass might be a little long compared to some factory brass. You would need to zero or calibrate your bump gauge to be certain.

Both new and once fired measure the same. all measurements are the same. I don't now how to say it any more clear

 

[fguffey]

If you ordered and they sent the correct 20° bump gauge insert, #749-011-477 per catalog 2015-B, for the 308 Winchester family of cartridges, then the insert alone is not to blame.

Again, I make datum based tools, I can also make tools that measure off of the shoulder with the correct shoulder angle I guess that is because this stuff does not lock me up. I guess it could be said I am the only one that understands the difference in the two. There are times I use datum and shoulder interchangeable.

F. Guffey

 

[Dusty Stevens]

Fran guffey is the only one here that isnt locked up over this- the only one who understands. And i got a hunch he will not tell us no matter what we do

 

[johnfred1965]

Do you have a dedicated depriming die, or were the cases sized when you deprimed and cleaned them?

 

['Freak]

Again, I make datum based tools, I can also make tools that measure off of the shoulder with the correct shoulder angle I guess that is because this stuff does not lock me up. I guess it could be said I am the only one that understands the difference in the two. There are times I use datum and shoulder interchangeable.

F. Guffey

This particular Sinclair bump gauge insert is machined same as the 20° angled chamber shoulder of everything in the 308 Winchester family and will fit over the neck of any of ‘em 30 caliber or less. The accepted shoulder datum diameter lands somewhere betwixt the neck hole and case body/shoulder junction. It’ll work fine for anybody, or maybe not so well fer folk wandering about hither and yonder in fgoofy land.

'Freak

 

[fguffey]

The accepted shoulder datum diameter lands somewhere betwixt the neck hole and case body/shoulder junction.

I suggested I could be the only one on this forum that understands the difference measuring from a datum and measuring from the shoulder. Someone suggested it would be nice to be able to zero the gage, I said I can do that and I assume all reloaders could accomplish the same task. And then; someone proves my assumption is not correct.

The accepted shoulder datum diameter lands somewhere betwixt the neck hole and case body/shoulder junction. It’ll work fine for anybody, or maybe not so well fer folk wandering about hither and yonder in fgoofy land.

I could have suggested a reloader learn to use standards and transfers. Problem; I would have to explain what a transfer is and how to use it and I would have to explain what a standard is and how it is used.

datum diameter lands somewhere betwixt the neck hole and case body/shoulder junction.

It is either or not both unless the reloader learns to zero with a standard and or transfer. Then there is going back in time before SAAMI.

F. Guffey

 

[BoydAllen]

This is all pretty silly if the object is to take measurements to properly set a die for shoulder bump. For that, no absolute measurement is necessary but rather a comparison of measurements taken with the same tool is all that is needed. For instance, if I were to intentionally set a caliper so that it read .010 with its jaws closed, and measured two things to see what the difference in their dimensions were, the caliper's being incorrectly zeroed would not be a problem. All that would be needed would be to subtract the smaller measurement from the larger. It is the same for using a caliper attachment to set a FL die for bump. As long as the attachment lands on the same place on the flat parts of the shoulders of both case those measurements can be used to accurately set a die for bump. I use an old Stoney Point caliper attachment for this task. Rather than having inserts that are at particular angles to match case shoulders, its inserts are designed to make line contact, and that is what I prefer. There are several inserts, with different IDs in the set, each marked with its ID. the edges that contact case shoulders are radiused. For setting bump I do not care what the chamber headspace is, I only need to know what the difference between the the case that I am using for a reference and one that I have sized is. On the other hand, I can take note of the measurement of a GO gauge and compare that with, new, fired and sized brass should I desire that information, but that would have nothing to do with setting a FL die for bump, and the absolute number would not matter, only the differences.

 

[7887mm08]

WOW thanks for all the help!

 

[7887mm08]

Ireload2 thankyou for your response this makes sense to me.

 

[7887mm08]

This is all pretty silly if the object is to take measurements to properly set a die for shoulder bump. For that, no absolute measurement is necessary but rather a comparison of measurements taken with the same tool is all that is needed. For instance, if I were to intentionally set a caliper so that it read .010 with its jaws closed, and measured two things to see what the difference in their dimensions were, the caliper's being incorrectly zeroed would not be a problem. All that would be needed would be to subtract the smaller measurement from the larger. It is the same for using a caliper attachment to set a FL die for bump. As long as the attachment lands on the same place on the flat parts of the shoulders of both case those measurements can be used to accurately set a die for bump. I use an old Stoney Point caliper attachment for this task. Rather than having inserts that are at particular angles to match case shoulders, its inserts are designed to make line contact, and that is what I prefer. There are several inserts, with different IDs in the set, each marked with its ID. the edges that contact case shoulders are radiused. For setting bump I do not care what the chamber headspace is, I only need to know what the difference between the the case that I am using for a reference and one that I have sized is. On the other hand, I can take note of the measurement of a GO gauge and compare that with, new, fired and sized brass should I desire that information, but that would have nothing to do with setting a FL die for bump, and the absolute number would not matter, only the differences.

I agree with your explanation It was just hard to understand that these different cases would all measure the same.

 

[BoydAllen]

Tell you what...PM me and we can make arrangements for you to send samples of all of the cases that you have questions about and I will measure them and report what I get in the way of differences.
Boyd

 

[7887mm08]

Tell you what...PM me and we can make arrangements for you to send samples of all of the cases that you have questions about and I will measure them and report what I get in the way of differences.
Boyd

pm sent

 

[ireload2]

It is true anyone can compare one case to another and move the die enough to push the shoulder back.
But that does not tell you the amount your new brass is going to stretch the first time it is fired. If it is stretching you don't know if it is the fault of the rifle or the new brass. Some of us want a little more information than "Did I move the shoulder .001 or was it really .002."

If you have 5 rifles and 7 loading dies all for the same cartridge you might like to know the exact dimensions to understand what the factories are producing. You can even match new brass to a rifle and FL die. I also use the Stoney point tool and find it has some built in error because the edge of the datum bores are broken about .004 to .005. It can be used for direct measurements if it is zeroed on a headspace gauge or a case of known length to the shoulder datum.

This is all pretty silly if the object is to take measurements to properly set a die for shoulder bump. For that, no absolute measurement is necessary but rather a comparison of measurements taken with the same tool is all that is needed. For instance, if I were to intentionally set a caliper so that it read .010 with its jaws closed, and measured two things to see what the difference in their dimensions were, the caliper's being incorrectly zeroed would not be a problem. All that would be needed would be to subtract the smaller measurement from the larger. It is the same for using a caliper attachment to set a FL die for bump. As long as the attachment lands on the same place on the flat parts of the shoulders of both case those measurements can be used to accurately set a die for bump. I use an old Stoney Point caliper attachment for this task. Rather than having inserts that are at particular angles to match case shoulders, its inserts are designed to make line contact, and that is what I prefer. There are several inserts, with different IDs in the set, each marked with its ID. the edges that contact case shoulders are radiused. For setting bump I do not care what the chamber headspace is, I only need to know what the difference between the the case that I am using for a reference and one that I have sized is. On the other hand, I can take note of the measurement of a GO gauge and compare that with, new, fired and sized brass should I desire that information, but that would have nothing to do with setting a FL die for bump, and the absolute number would not matter, only the differences.