Setting up sizing die - Wide range of BTS measurements on fired brass???

[MoneyWaster]

Unless all your initial loads were fairly hot, you can expect considerable variation in base-to-shoulder measurement. Run loads through all those cases again, preferably all hotter loads, sizing necks only, then measure them again.

Did you happen to measure the shoulders of any virgin cases? Keep in mind it's not unusual for them to have on the order of .008" headspace (in mass-produced chambers anyway - yours may well be tighter.) so there's a considerable range they can settle within after one firing if the loads range from mild to hot. The softness and consistency of the brass has a bearing on this as well.

If you are not sure about your measurement tool / technique, just record the measurements for 5 or 10 cases chosen at random, then go back and measure them again, see if you duplicate all the original values.
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I did not measure the virgin cases. In hindsight I should have.

FWIW, I neck sized all the cases and left the shoulder alone. I'll revisit the measurement again after they are fired.

 

[Bart B.]

Keep in mind it's not unusual for them to have on the order of .008" headspace

Don't you mean head clearance?

 

[Bart B.]

You can take a fired case that has not fireformed all the way, insert a spent primer partly into the primer pocket. Chamber the brass with the primer sticking out and let the bolt shove the primer into the pocket when closing the bolt.

I've had loads about 15% below max end up with primers backed out .007" from Federal nickel plated 308 Win once fired cases that started out new .002" less in headspace than the chamber's 1.6305" headspace.

 

[Brians356]

Don't you mean head clearance?

Strictly speaking, yes, thank you. But in common vernacular we also refer, for example, to "excess headspace" to describe the clearance of a particular case inside a particular chamber. That usage does not appear in a SAAMI glossary of terms, but few here would misconstrue the meaning. And hence Hornady's "Headspace Gauge" which measures cases, not chambers.
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[Brians356]

... 308 Win once fired cases that started out new .002" less in headspace than the chamber's ... headspace.

You just used "headspace" to describe a fired case. Sad!
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[Bart B.]

What if that clearance or excessive space is between case shoulder and chamber shoulder because the the case head is hard against the bolt face?

 

[Brians356]

What if that clearance or excessive space is between case shoulder and chamber shoulder because the the case head is hard against the bolt face?

Ooh, I love trick questions! If the case was formed with a false shoulder (e.g. had a partially sized-down neck) then it could still have clearance as measured at the datum, but it wouldn't really have any effective "headspace" at all (excessive or otherwise.) Another example would be a 250 Savage case in a 250 AI chamber, where the barrel has been set back a turn or so to form a crush fit at the neck/shoulder junction.

Chicken dinner?
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[Bart B.]

If the case was formed with a false shoulder (e.g. had a partially sized-down neck) then it could still have clearance as measured at the datum, but it wouldn't really have any effective "headspace" at all (excessive or otherwise.)

Yes, clearance at the case shoulder. The case will still have headspace from its head to its shoulder datum. And it's back end will have zero head clearance as its against the bolt face.

Same thing with a standard case with bullet seated tight and extra long to be forced partially into the lands and grooves. It's head is against the bolt face and there's shoulder clearance.

You just used "headspace" to describe a fired case. Sad!

Nope. Used headspace to refer to the case dimension from its head to its shoulder datum.

 

[Brians356]

Same thing with a standard case with bullet seated tight and extra long to be forced partially into the lands and grooves. It's head is against the bolt face and there's shoulder clearance.

I trust a false shoulder more than a seated bullet to keep the case against the bolt face as long as possible when fire forming. It always seemed to me the neck would expand away from the bullet relatively early in the pressure build-up, but many claim it is effective.
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[fguffey]

My 2 RCBS Rockchuckers, Partner and Junior press all cam over when the die bottom's pressed hard by shell holders ramming up tight to it. My presses are not the only ones that do that. Steel stretches.

As I have said before life is not fair to you, my Rock Chuckers lock up, jam up and or cram up, the bottom of the ram is kicked back and the top of the ram is kicked forward, all that is required of a reloader that owns one is to push themselves away from the key board and then crawl under the bench to watch it run; or, unbolt the Rock Chucker and watch it run. The Rock Chucker goes into a big bind before the ram changes directions.

I am the only reloader that has had a Rock Chucker that camed over, I ground the contact points for clearance, after grinding the bottom of the ram was did not get kicked back and the top of the ram did not did not get kicked forward. And then there was the utube crowd, they made a video of the ram kicking forward and blamed it on the Chinese. They did not understand the case in the shell holder on the bottom held the ram straight when the case aligned with the die. If a reloader does not want the ram to kick forward at the top install a case in the shell holder, or, push your self away from the key board and run that ram up and down and watch the top of the ram kick forward when the linkage gets tangled when it goes into a bind.

Steel stretches.

but it does not change direction, I have 12 cam over presses, all of my cam over presses have a ram that goes up, stops and then changes directions. And that is how the cam over press got to be called the 'bump' press before the Internet.

F. Guffey

 

[fguffey]

You just used "headspace" to describe a fired case. Sad!
Click to expand...
Nope. Used headspace to refer to the case dimension from its head to its shoulder datum.

SAMMI said the case does not have head space, and then there was the Digital Head space gage, the digital gage was a comparator, problem: Finding smiths and reloaders that knew the difference. The case gage, that was another one, for years reloaders called it a drop in gage, and still there are those that call it a head space gage. The case does not have head space.

F. Guffey

 

[ireload2]

Hey guffey what comes out of a fire hose?

SAMMI said the case does not have head space, and then there was the Digital Head space gage, the digital gage was a comparator, problem: Finding smiths and reloaders that knew the difference. The case gage, that was another one, for years reloaders called it a drop in gage, and still there are those that call it a head space gage. The case does not have head space.

F. Guffey

 

[ireload2]

Without photos it didn't happen.

I have 12 cam over presses, all of my cam over presses have a ram that goes up, stops and then changes directions. And that is how the cam over press got to be called the 'bump' press before the Internet.

F. Guffey

 

[Bart B.]

It always seemed to me the neck would expand away from the bullet relatively early in the pressure build-up, but many claim it is effective.

That's the way it works.

If a 30 caliber bullet needs 80 pounds of force to push it out of the case and into the rifling, pressure in the case will have to be almost 1100 psi. That may let some gas blow by the bullet. But as soon as the bullet obturates 100% to bore cross section filling the grooves, pressure starts up quick and peaks when the bullet is 5 to 6 inches more into the barrel. This all happens in a few tenths of a millisecond.

Someone did some tests years ago with weights pushing bullets an inch or more into the rifling. I don't remember when nor the weights needed for the 30 caliber bullets used.

 

[Brians356]

Seems reasonable. But a false shoulder seems even better, if it's a practical option. Personally, I form Ackley cases "bulletless", and don't take special pains with regular cases.
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[Brians356]

I have 12 cam over presses

Those must make some sweet music when you get them all going! What's the firing order?
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[fguffey]

If a 30 caliber bullet needs 80 pounds of force to push it out of the case and into the rifling,

Before the Internet it was called bullet hold, today I want all the bullet hold I can get, I struggle to get more than 40 pounds of bullet hold but I seem to be the only reloader that can measure the effort required to seat a bullet and push it out. And I wonder why that is? It could be because most reloaders use tensions, tensions? They do all of that without a gage that measures tensions and they do that with no conversion for tensions but still they use tensions. I have said I have tensions gages; none of my tension gages measure tensions, all of my tension gages are calibrated in pounds. I also have a deflection gage, it measures deflection in thousandths and inches.

Back to the Rock Chucker, if the Rock Chucker camed over one of the Rock Chucker owners would have already took his hands out of his pockets and or backed himself away from the ley board and made a video. Metal stretches? A reloader with shop skills and understood how a deflection gage works could determine if the RC stretched. And they could determine if the ram went up, stopped and then started back down. One more time, my RC attachments will not tolerate a change in direction of the ram. My attachments have a one way clutch because my attachments are auto advance.

F. Guffey

I suggest reloader read R. Lee's book on modern reloading, he covers bullet release, pressure and time. Again, I am the fan of all the bullet hold I can get.

 

[fguffey]

pressure starts up quick and peaks when the bullet is 5 to 6 inches more into the barrel.

I understand everyone reading this thread believe you but me. I have said forever I am the fan of 'the bullet jump' I want my bullets to have that running start; I do not want my bullet setting at the lands trying to decide if it is going to make it past the rifling. What does that mean? If I have spike it will be when the bullet hits the rifling meaning when the bullet passes the rifling the pressure starts to drop. And then there was that thing about magic, a smith in Iowa Park, Tx blew the end of barrels put on a regular bases.

Serious spikes: A shooter in central North Texas took a rifle to the range with a new box of ammo. The rifle did not belong to him. He chambered a round from a newly purchased box of ammo, he pulled the trigger and then headed to a gun smith. The shooter purchased 308 W ammo for his friends 25/06. The shooter was going to sue all involved. It was not possible to read the head stamp on the 308W case.

F. Guffey

 

[kountryboy2]

I suggest reloader read R. Lee's book on modern reloading, he covers bullet release, pressure and time. Again, I am the fan of all the bullet hold I can get.

Now I know you are a nut case.

 

[Bart B.]

Before the Internet it was called bullet hold,

USA military arsenals spec'd bullet release or extraction forces for all small arms ammo back in the 1950's. What's in a name? Whatever your want it to be. But the process is the same.