Fire Forming Question

[harry_x1]

This is probably a silly question for many, but asking as I am new to reloading and want to avoid accidents.

Q: Once a brass is fired in a chamber, is the fire formed brass, when reloaded second time, provide a less headspace than before? or is it the other way around, the headspace increases post fire forming?

 

[PinesAndProjectiles]

Headspace within the chamber should not change.
But if you’re measuring from the base of the brass to the datum on the shoulder, that measurement should increase after firing.
But, not all brass and/or chambers are created equally.
So, it may take another firing for the brass to fully expand.

 

[harry_x1]

Headspace within the chamber should not change.
But if you’re measuring from the base of the brass to the datum on the shoulder, that measurement should increase after firing.
But, not all brass and/or chambers are created equally.
So, it may take another firing for the brass to fully expand.

So if the case base to shoulder datum has increased, will we now have less space between case shoulders and chamber shoulder cut? Basically there will be less free space for case to move freely inside chamber (in turn less functional headspace)?

If that is true, I am assuming that a fire formed brass basically reduces functional headspace (space for free movement of case inside chamber) ?

 

[918v]

Fire formed brass fills out the chamber so yes, less headspace after.

 

[Dthomas3523]

So if the case base to shoulder datum has increased, will we now have less space between case shoulders and chamber shoulder cut? Basically there will be less free space for case to move freely inside chamber (in turn less functional headspace)?

If that is true, I am assuming that a fire formed brass basically reduces functional headspace (space for free movement of case inside chamber) ?

Yes, it will “move” or expand less once fireformed.

Keep in mind, depending on the brass and chamber, it may take more than one firing to fully fireform where you need minimally size the case for proper function.

 

[harry_x1]

thanks all for the quick clarification.

 

[spife7980]

A little terminology
“Headspace is the distance measured from a closed chamber's breech face to the chamber feature that limits the insertion depth of a cartridge placed in it.” Aka, it’s a relationship between the action and the barrel, ammo has no bearing on how the rifle is headspaced. The gun gets headspaced, not the ammo.

So basically what we are looking at with a case inside of the chamber comparing virgin vs fired vs sized isn’t headspace but rather headspace clearances.

So no, headspace doesn’t change unless the barrel spins in or out.
But the clearances between the chamber and the brass do change. When it’s fired the brass fills the chamber and springs back a smidge. So yes, if the brass started smaller and got bigger when fired there will be less empty space between the case and the chamber afterwards. But considering how much extra space there is on a second firing like you asked depends entirely on how much you sized it between trigger pulls.

 

[harry_x1]

A little terminology
“Headspace is the distance measured from a closed chamber's breech face to the chamber feature that limits the insertion depth of a cartridge placed in it.” Aka, it’s a relationship between the action and the barrel, ammo has no bearing on how the rifle is headspaced. The gun gets headspaced, not the ammo.

So basically what we are looking at with a case inside of the chamber comparing virgin vs fired vs sized isn’t headspace but rather headspace clearances.

So no, headspace doesn’t change unless the barrel spins in or out.
But the clearances between the chamber and the brass do change. When it’s fired the brass fills the chamber and springs back a smidge. So yes, if the brass started smaller and got bigger when fired there will be less empty space between the case and the chamber afterwards. But considering how much extra space there is on a second firing like you asked depends entirely on how much you sized it between trigger pulls.

thanks for clarifying and sharing your knowledge. I was ignorantly using the word headspace to denote the amount of free space within which 'a particular case' is able to move freely inside 'a particular' chamber. But you are right, that probably is incorrect terminology...thanks

 

[spife7980]

thanks for clarifying and sharing your knowledge. I was ignorantly using the word headspace to denote the amount of free space within which 'a particular case' is able to move freely inside 'a particular' chamber. But you are right, that probably is incorrect terminology...thanks

We use the term a lot here on the forum, we just use it incorrectly most of the time lol
You seem to be grasping the underlying concepts though.