Surprise measuring once fired brass

13 February 2021, 05:27

I picked up a Steyr pro-hunter a couple of years ago (it may be butt-ugly but it’s accurate) in .270. I’ve shot 4 boxes of Winchester factory ammo, purchased at different times so different lots) and kept all the brass. I decided it was time to reload so I measured all of the brass with a Stoney Point “head and shoulder” gauge and the length (case head to datum line on shoulder) varied as much as .003. I was so surprised I remeasured every piece with the same result.

Is this level of variation normal in once fired brass from the same rifle?

13 February 2021, 06:11

dpcd

Three thousandths? That is nothing, in the context.
You need to read the SAAMI spec book; tolerances between brass, ammo, chambers, and dies are positively HUGE.
Throw your gauge in the trash; it tells you nothing useful; make the ammo fit your chamber. Your chamber, and only that one, is your gauge. Adjust your dies to suit; If you do not know how to do that, ask.

13 February 2021, 11:47

Reloader270

quote:
Originally posted by dpcd:
Three thousandths? That is nothing, in the context.
You need to read the SAAMI spec book; tolerances between brass, ammo, chambers, and dies are positively HUGE.
Throw your gauge in the trash; it tells you nothing useful; make the ammo fit your chamber. Your chamber, and only that one, is your gauge. Adjust your dies to suit; If you do not know how to do that, ask.

Measuring sometimes cause more confusion. Concentrate on your shooting skills and you would find that all these differences does not count that much.

13 February 2021, 13:02

Saeed

quote:
Originally posted by belaw:
I picked up a Steyr pro-hunter a couple of years ago (it may be butt-ugly but it’s accurate) in .270. I’ve shot 4 boxes of Winchester factory ammo, purchased at different times so different lots) and kept all the brass. I decided it was time to reload so I measured all of the brass with a Stoney Point “head and shoulder” gauge and the length (case head to datum line on shoulder) varied as much as .003. I was so surprised I remeasured every piece with the same result.

Is this level of variation normal in once fired brass from the same rifle?

I am a bit confused here, as I know nothing about this tool.

I am assuming this measures what we would normally call headspace for that rifle, am I correct?

Are you measuring this after each one was fired, and before resized?

13 February 2021, 16:59

p dog shooter

quote:
I measured all of the brass with a Stoney Point “head and shoulder” gauge and the length (case head to datum line on shoulder) varied as much as .003. I was so surprised I remeasured every piece with the same result.

So I have loaded 10's of thousands of rifle rounds I don't think I have measure more than a hundred. If they fit I load them if they don't I trim them.

13 February 2021, 18:04

belaw

quote:
Originally posted by Saeed:

I am a bit confused here, as I know nothing about this tool. I am assuming this measures what we would normally call headspace for that rifle, am I correct?

Correct - it’s just a headspace comparator. The current version is made by Hornady under the Lock-n-Load name.

quote:
Originally posted by Saeed:

Are you measuring this after each one was fired, and before resized?

Yes; once fired and not resized.

I try to load hunting rounds with a couple of thousands headspace clearance and yes, I use the chamber as my gage. I stripped the bolt and it dropped on both the “long” and “short” brass; the longest brass had just a hint of a crush fit, so I’m going that to set up my resizing die to push the should back just a touch.

What I am asking is what level of headspace consistency should I see in brass that has been “fireformed” in the same chamber? I understand different lots of brass will have different hardness and ‘springback’ elasticity but I was surprised at variation in headspace length in the fired brass.

13 February 2021, 18:39

Saeed

My suggestion is to load them and shoot them.

And not worry about these differences as long as your rifle shoots as you expect.

Modern factory rifles are very easily shoot 1 inch at 100.

Many would shoot better with loads they like.

A few, would be very hard put to break 1.5 inch groups, as they come from the factory.

This has been my experience with rifles brought here from practically all well known manufacturers.

13 February 2021, 20:16

dpcd

NOOOOOOOOOO!!!!!
Please stop talking about "headspace" in terms of your brass.
That tool DOES NOT measure headspace of your rifle in any way. It might, (or might not) give a very rough idea of how your brass reacted to your chamber. Headspace is only a rifle measurement; not related to ammo, and can only be measured with gauges, and when we do that, it is not usually really measured; just go and no go, which is about .004 difference. Depends on the maker of the gauge. Again, the tolerance between a minimum ammo and a max chamber is up to .016.
As stated by Saeed and others, Load, (correctly; do not size your brass to much and if you need help, post that again), and shoot it.
Forget that little gauge; it just confuses people. Hornady has to make money somehow, don't they?

13 February 2021, 23:20

whelenite

The hardness of the brass and the pressure of each load will make each round fired, even in the same chamber, stretch under pressure and then spring back differing amounts. Your results are completely normal.

14 February 2021, 01:49

bigrdp51

quote:
Originally posted by dpcd:
NOOOOOOOOOO!!!!!
Please stop talking about "headspace" in terms of your brass.
That tool DOES NOT measure headspace of your rifle in any way. It might, (or might not) give a very rough idea of how your brass reacted to your chamber. Headspace is only a rifle measurement; not related to ammo, and can only be measured with gauges, and when we do that, it is not usually really measured; just go and no go, which is about .004 difference. Depends on the maker of the gauge. Again, the tolerance between a minimum ammo and a max chamber is up to .016.
As stated by Saeed and others, Load, (correctly; do not size your brass to much and if you need help, post that again), and shoot it.
Forget that little gauge; it just confuses people. Hornady has to make money somehow, don't they?

How many gauges would Hornady sell if they called then head clearance gauges.

Below I'm measuring a fired case from my AR15, I then set the resizing die up for .003 shoulder bump.

14 February 2021, 03:28

B L O'Connor

quote:
Originally posted by bigrdp51:
quote:
Originally posted by dpcd:
NOOOOOOOOOO!!!!!
Please stop talking about "headspace" in terms of your brass.
That tool DOES NOT measure headspace of your rifle in any way. It might, (or might not) give a very rough idea of how your brass reacted to your chamber. Headspace is only a rifle measurement; not related to ammo, and can only be measured with gauges, and when we do that, it is not usually really measured; just go and no go, which is about .004 difference. Depends on the maker of the gauge. Again, the tolerance between a minimum ammo and a max chamber is up to .016.
As stated by Saeed and others, Load, (correctly; do not size your brass to much and if you need help, post that again), and shoot it.
Forget that little gauge; it just confuses people. Hornady has to make money somehow, don't they?

How many gauges would Hornady sell if they called then head clearance gauges.

Below I'm measuring a fired case from my AR15, I then set the resizing die up for .003 shoulder bump.

I've never loaded a round where the primer protrudes like the one in the figure.

My primers are seated deep to the head's surface.

So there are few thousandths of clearance between the primer and the bolt rather than the case head and the bolt.

14 February 2021, 03:43

dpcd

Measuring a fired case does not necessarily tell you how long your chamber is, due to many factors. I still feel it can give reloader a false idea of what they are doing; due to the fact that different brass can obturate, and spring back, differently. Brass is not a good material for a gauge.
Makes guys feel good though, thinking they are being "precise".
Precision, is not, accuracy.

14 February 2021, 05:08

belaw

quote:
Originally posted by whelenite:
The hardness of the brass and the pressure of each load will make each round fired, even in the same chamber, stretch under pressure and then spring back differing amounts. Your results are completely normal.

Thanks - this is what I was asking!

quote:
Originally posted by dpcd:
NOOOOOOOOOO!!!!!
Please stop talking about "headspace" in terms of your brass.

Annnnddd this exactly why I didn’t use the word “headspace” in my original post; yes, the term is commonly used to refer to brass length measured from case head to the datum line - even though most of us know that it is technically inaccurate. As Saeed said, “I am assuming this measures what we would normally call headspace for that rifle.” The problem with using the term to describe this measurement is that someone invariably chimes in at some point in the conversation to tell everyone they’re using the term incorrectly which starts a heated debate that goes on for multiple forum pages....

14 February 2021, 06:35

bigrdp51

[/QUOTE]I've never loaded a round where the primer protrudes like the one in the figure.

My primers are seated deep to the head's surface.

So there are few thousandths of clearance between the primer and the bolt rather than the case head and the bolt.[/QUOTE]

I do not load any cartridge with a protruding primer either. BUT at low pressure the primer will protrude. Also the primer method is used to measure your head clearance.

Below you can measure the rim thickness and the primer protrusion and it will give you the actual chamber headspace.

14 February 2021, 06:42

Lamar

I'm with Whelanite.
don't make this difficult or overthink it.

measure what you got, neck size, anneal, trim and size back to some sort of measurement you come up with.
you'll feel better about it,, and,,, well, that's all that matters.

14 February 2021, 06:45

bigrdp51

quote:
Originally posted by dpcd:
Measuring a fired case does not necessarily tell you how long your chamber is, due to many factors. I still feel it can give reloader a false idea of what they are doing; due to the fact that different brass can obturate, and spring back, differently. Brass is not a good material for a gauge.
Makes guys feel good though, thinking they are being "precise".
Precision, is not, accuracy.

And in many of your postings you tell us you don't use any gauges. "BUT" you will use a case and bolt closing effort to determine your headspace and approximate head clearance.

And then you tell us "Precision, is not, accuracy."

14 February 2021, 07:46

B L O'Connor

quote:
I do not load any cartridge with a protruding primer either. BUT at low pressure the primer will protrude. Also the primer method is used to measure your head clearance.

Below you can measure the rim thickness and the primer protrusion and it will give you the actual chamber headspace.

I'm honestly not trying to be perverse, but how do you know how to reduce pressure enough to get the case molding itself (maximally) to the chamber's dimensions, but minimally enough so that the primer becomes maximally protruded?

I'd imagine that there is such a point, but in practice how do you determine it in terms of amount of powder and protrusion of primer?

I assume it's by trial and error: you must find a powder charge that produces maximum case expansion along with maximum primer protrusion. Seems to me that too little pressure and you don't get enough case expansion, too much pressure and you reseat the primer (partially or completely).

Not trying to be difficult, but I honestly don't know.

Maybe, if trial and error is the process, FL resizing in increments and trying the case in a rifle's chamber after each change might be more economical and faster.

14 February 2021, 19:40

Lamar

by the time you get through finding that pressure point you've worn the case out.

and didn't take into account the firing pin banging the case shoulder off the chamber shoulder pushing it back.
so now you've gone the other way with your measurement just to get the primer to stick out.

[rolling my eyes]

14 February 2021, 20:09

dpcd

Bigrp; you might have misinterpreted my intent; totally my fault. But the fact is that measuring a find case will not tell you much of value; brass is too variable a medium to interpolate a chamber dimension from. I mean from which to....
You simply do not know where the starting point is because the brass has already pulled back from the chamber. Doing it that way is largely a feel good exercise, which, although precise (for that one case only), is not an accurate representation of exactly how much clearance you have, is usually harmless.
But, if you start with a long case (all of them actually, then you can get a better feel of how the case fits into the chamber. Your chamber only. Read below:
Do what BL O. said to do in his last sentence. All your problems will be solved, using no case gauges. And it will stop your mag brass from separating too.
And no, Precision is not Accuracy.

14 February 2021, 22:54

dpcd

Got a note about not understanding the Precision vs Accuracy thing; it is easy to understand and here is an example.
My wife has a clock in the kitchen that tells time to within one second. That is a very precise measurement of time for any practical purpose. The problem is that she sets it 5 minutes fast. So, while it is a very precise measurement, it is not accurate at all.
Not a comment about rifle accuracy, although it could be; say you had a group of .2 inches for 5 shots, but it was hitting 2 feet from the desired target.

15 February 2021, 00:38

bigrdp51

quote:
Originally posted by B L O'Connor:
quote:
I do not load any cartridge with a protruding primer either. BUT at low pressure the primer will protrude. Also the primer method is used to measure your head clearance.

Below you can measure the rim thickness and the primer protrusion and it will give you the actual chamber headspace.

I'm honestly not trying to be perverse, but how do you know how to reduce pressure enough to get the case molding itself (maximally) to the chamber's dimensions, but minimally enough so that the primer becomes maximally protruded?

I'd imagine that there is such a point, but in practice how do you determine it in terms of amount of powder and protrusion of primer?

I assume it's by trial and error: you must find a powder charge that produces maximum case expansion along with maximum primer protrusion. Seems to me that too little pressure and you don't get enough case expansion, too much pressure and you reseat the primer (partially or completely).

Not trying to be difficult, but I honestly don't know.

Maybe, if trial and error is the process, FL resizing in increments and trying the case in a rifle's chamber after each change might be more economical and faster.

P.O. Ackley did an experiment with a 30-30 Winchester 94 and removed the locking bolt and remotely fired the rifle. Nothing happened, the case gripped the chamber walls and all that happened was the primer backed out. At the max pressure of 42,000 psi the pressure was not great enough to make the case stretch back to contact the bolt face.

When you make a workup load starting at the suggested starting load the primers will protrude. The primers do not become flush until the chamber pressure is high enough to push the case to the rear to contact the bolt face.

Below firing a .303 British in a Enfield rifle at 46,000 psi and the case stretching and thinning to contact the bolt face. At 42,000 psi the 30-30 case does not stretch and only the primer backs out.

15 February 2021, 01:01

bigrdp51

quote:
Originally posted by belaw:
I picked up a Steyr pro-hunter a couple of years ago (it may be butt-ugly but it’s accurate) in .270. I’ve shot 4 boxes of Winchester factory ammo, purchased at different times so different lots) and kept all the brass. I decided it was time to reload so I measured all of the brass with a Stoney Point “head and shoulder” gauge and the length (case head to datum line on shoulder) varied as much as .003. I was so surprised I remeasured every piece with the same result.

Is this level of variation normal in once fired brass from the same rifle?

The case will spring back from the chamber walls after being fired. The amount the case springs back depends on the brass hardness and chamber pressure.

And when full length resizing if you pause at the top of the ram stroke for a few seconds it reduces brass spring back. Meaning the shoulder location will be more uniform when measured.

15 February 2021, 01:34

dpcd

That is a very cool little demo video; not sure what to call it. Simulation?

15 February 2021, 07:49

bigrdp51

It's an animated image of a .303 British being fired in a Enfield rifle.

At the max military headspace of .074 and a rim thickness of .058 you will have .016 head clearance.

The Enfield is famous for case head separations if the cases are full length resized.

An old trick to fire forming these cases was to slip a small thin rubber o-ring around the case. this holds the case against the bolt face and the case can not stretch.

Thereafter you neck size only and let the case headspace on its shoulder and not the rim.

15 February 2021, 20:05

B L O'Connor

Thanks!

I always enjoy learning. And the rubber ring trick with .303 is quite ingenious.

Love the animations and graphics, too.

15 February 2021, 20:07

dpcd

How do you make those animations?
Buy an nimation program?

16 February 2021, 19:55

F. Guffey

quote:
Originally posted by belaw:
I picked up a Steyr pro-hunter a couple of years ago (it may be butt-ugly but it’s accurate) in .270. I’ve shot 4 boxes of Winchester factory ammo, purchased at different times so different lots) and kept all the brass. I decided it was time to reload so I measured all of the brass with a Stoney Point “head and shoulder” gauge and the length (case head to datum line on shoulder) varied as much as .003. I was so surprised I remeasured every piece with the same result.

Is this level of variation normal in once fired brass from the same rifle?

"Is this level of variation normal". Depends on who is measuring and then there is the Hornady tool. From the beginning the Sinclair/Hornady tool had a flaw; it seems they started out being nice to the case. They placed a radius on the edge of the tool, I understand that means nothing to reloaders that invented reloading. When I make a tool with a datum the datum must be cut to 90 degree to the perpendicular of the hole; I want a sharp edge on the datum. The Hornady radius creates an error that can be off by as much as .003".

And then they decided to mount their tool onto a contraption 'dial indicator' it was never necessary; they can not 'zero' the tool.

L.E. Wilson makes a case gage, it is a precision gage with a datum that has a radius.

F. Guffey

18 February 2021, 09:14

Wstrnhuntr

Happiness is a tight chamber.

18 February 2021, 17:31

DocEd

Nearly every dial caliper made, regardless of price, does not claim accuracy better than + or - .002".

18 February 2021, 20:30

dpcd

I strongly disagree with the last two posts. Tight chambers make more shooters UN happy than Happy, from what I have seen.
And you can't expect better than .004 accuracy? I have tested my Mitutoyo against calibrated micrometers, and it is far closer than that.
That doesn't mean that measuring fired brass tells you anything of value.
It doesn't.
Measuring the length of a fired case and expecting it to be representative of anything is like measuring silly putty.

18 February 2021, 20:50

DocEd

quote:
I have tested my Mitutoyo against calibrated micrometers, and it is far closer than that.
That doesn't mean that measuring fired brass telI have tested my Mitutoyo against calibrated micrometers, and it is far closer than that.
That doesn't mean that measuring fired brass tells you anything of value.ls you anything of value.

You got a good set. Read the manufacturers claim.

24 February 2021, 05:28

Atkinson

Brass cases usually need to be trimmed at 2 to 4 firing or your sticking the case mouth into the rifleing not allowing it to expand is pretty common knowledge..

I also mic new case heads, then again after firing and .001 or .002 is OK I guess but .005 is not an thats when stick bolts become apparant it seems.

You can measure headspace by measuring the protrusion of the primer most of the time,and can do the same with two layers of electrictions tape as far a go and no go goes..