How much sizing is appropriate?

['Freak]

The amount of clearance or crush depends on the use of the rifle.

... So, short bench guys want cases to have no crush - maybe 0.001" or 0.002" of empty space.

Long range shooters, who do not shoot fast inside of a wind "window" can benefit from more crush, cuz it leads to very long case life - I have thrown away cases with almost 50 firings (and they were still fine, but I wanted to upgrade to Lapua), and other guys have 80 to 100 firings on their cases - for that, you need 2 to 4 or more thou of crush.

I prefer to feel a fair amount of resistance on the bolt handle when I close the bolt. There are no stress "problems" induced. The rifle closes tight, and it is fine. After all, once you pull the trigger, THEN the stress happens - in spades !!

When you cam the bolt closed so it’s crushing a case that‘s .004” or more longer from case head to shoulder datum than the chamber is long from bolt face to chamber shoulder datum, how is that using the bolt to force fit the longer case to the shorter chamber not working the brass pretty much the same as you would be if you shoving the shoulder back .004” or more in a size die?

Then once you’ve used the bolt to crush fit the case down to the same length as the chamber, and you fire that thang, how else but by bolt lug yield and by the action stretching is it possible to make the bolt face to chamber shoulder datum length long enough so that after getting the bolt back open, the case exits expanded out again to .004” or more longer than the action’s at rest bolt face to chamber shoulder datum length?

 

[XBBR Shooter]

When you cam the bolt closed so it’s crushing a case that‘s .004” or more longer from case head to shoulder datum than the chamber is long from bolt face to chamber shoulder datum, how is that using the bolt to force fit the longer case to the shorter chamber not working the brass pretty much the same as you would be if you shoving the shoulder back .004” or more in a size die?

Then once you’ve used the bolt to crush fit the case down to the same length as the chamber, and you fire that thang, how else but by bolt lug yield and by the action stretching is it possible to make the bolt face to chamber shoulder datum length long enough so that after getting the bolt back open, the case exits expanded out again to .004” or more longer than the action’s at rest bolt face to chamber shoulder datum length?

Huh??? Datum, schmatum... this is not about datum.

When you fire a case, it will stretch to fit the chamber - but it will spring back a tiny bit. With repeated firings, the case will grow to be slightly longer than the chamber. How much depends on the action, and the fitment of the bolt (system flex). The case will reach an equilibrium where the amount that it is longer,is equal to the amount of action flex... it is a good place to be, unless you are a PBBR shooter.

 

['Freak]

Huh??? Datum, schmatum... this is not about datum. ...

From where then to what does I suppose to be measurin’ to figger whether or not I gots me 2 to 4 or more thousand of them there crush doflotchies, cuz I need ‘em?

 

[XBBR Shooter]

From where then to what does I suppose to be measurin’ to figger whether or not I gots me 2 to 4 or more thousand of them there crush doflotchies, cuz I need ‘em?

Which "Datum line" do you want to use???
The "Datum line" is actually a large range of lines - same with cases... so which do you want to use??

 

['Freak]

The diameter at the shoulder datum line of the junk I’m shootin’ is, according to Hornady, .330” for their “A” and .400” for their “D” bushings, which I assume are bored to something rite close to the SAAMI shoulder datum diameters as listed, so will contact the case shoulders wherever along the shoulder its diameter is as equally something rite close, close here being a plenty enough.

My preference is for Sinclair’s Bump Gauge Inserts which instead of being simply an orifice of a particular diameter, Sinclair’s insert is machined to fit a particular shoulder angle. Their 17°, 20°, 23°, and 30° shoulder angle inserts cover what all I’m shootin’. Sinclair’s insert and Hornady’s bushing will work with either Sinclair’s or Hornady’s comparator body. I have Hornady’s “fits all” case head anvil base, but I prefer Davidson’s base pieces with each step machined to fit, and to better center, three different case head diameters.

I also use Wilson's case gauges but find ‘em more useful when something is used to actually measure how much the case head protrudes or is still below one of the gauge’s steps. While a caliper will work, I can use to read a Wilson gauge, the same doohickey that with dial indicator mounted, I use to read the position of the case head relative to a T/C Contender barrel’s breach face.

I have one RCBS “Precision Mic” headspace tool which same as the others, it gets me a reference number, only this one cost me fifty bucks...

Only the tool for directly reading case head position in a T/C barrel, when combined with a feeler gauge, is able to give me the actual “headspace” of a piece of brass in that one barrel.

All the others I use in specific combinations to arrive at some sort of a “standard” reference measurement of a case that I’ve manipulated to perfectly fit my chamber in a specific way, that being right at .0000” headspace. Then when I measure any other case and compare its “number” to my “standard” reference measurement number, and provided I used exactly the same combination of instrument and thingamajigs to measure both, I’ll know very near exactly how much clearance there’ll be betwixt the bolt face and the case head, or how much the case is gonna be crushed, when I close the bolt, capturing that case inside that chamber.

 

[MagnumManiac]

I agree with Donovan, I too, have a pressure trace. I also found jammed bullets completely change the curve, start pressure was and is more uniform, but, total time under the curve varied too much for my liking. I no longer load closer than .010". I DO NOT shoot BR, so there parameters are different to mine.
I have found loose cases to be more accurate than tight cases. Also, neck sized cases were not as accurate as a bumped case. I also found that certain brands of brass liked more or less bump in conjunction with more or less neck tension.
I anneal my cases after every firing before sizing, and the different brands definitely like different 'sets'.
I have never found a tight case or a neck sized case to be as accurate as a slightly loose case, ever.