There seems to be a lot of confusion and misinformation on Headspace. Headspace is the distanced between the head of a chambered cartridge and the breech face. When you gauge a chamber you are measuring the distance from the breech face to a point where the shoulder has a specific dimension. It depends on the dimension of the cartridge if headspace exists or not.
an empty chamber cannot have headspace there being no head present.
Good luck!

Hawkins, I think you momma sent you to the wrong school

quote:

Originally posted by hawkins:
There seems to be a lot of confusion and misinformation on Headspace.

When you gauge a chamber you are measuring the distance from the breech face to a point where the shoulder has a specific dimension.

How about citing an example of the confusion and misinformation that prompted this thread? And FWIW, belted and rimmed cartridges don't headspace on the shoulder.

It's the measurement from the bolt face to a specific datum line (point), which may be at some diameter on the shoulder, or it may be the end of the belt, forward surface of a rim, etc... The fact that you're trying to get into semantics on whether there is a 'headspace' depending on if there is a case chambered or not is trivial. Does a chamber with .100" freebore not have any freebore if you seat a bullet to touch the lands???????

Hawkins
Please read this. It should help you understand headspace. http://www.surplusrifle.com/sh.../headspace/index.asp

Bottle necked cartridges from the bolt face to the specific point on the datum line on the shoulder. On rimmed cartridges from the bolt face to the rear face of the barrel chamber. On straight rimless cartridges from the bolt face to the case mouth shoulder in the chamber. On belted cartridges from the bolt face to the rim shoulder in the chamber. When I say bolt face that also can be interpreted as frame directly behind the chamber such as in a revolver, or as in a single shot rifle or shotgun, and the face of a slide such as in semi automatic pistols. There is no such thing as excessive head space because head space is a specific set figure for all cartridges. Either it's is correct or it isn't. A firearm can have head space whether there is round chambered or not. The amount that exists if there is more space or less space then the correct head space figure is called excess clearance or not enough clearance. This is measure with various gauges such as go gauge, no go gauge, field gauge, preassembly guage, etc.. A firearm where the bolt or breech face gets set back is said to be out of correct head spacing...not that it developed excessive head space. That's my two cents.

Excellent link, Jeffeosso...a picture is worth much more than a 1000 words in this case(pun intended) and also should serve to correct the millions of words already written in an attempt to define "HEADSPACE". I wonder just how much dandruff has been shed in head scratching over "what IS headspace".

The part about tolerance stacking should be read, re-read, and committed to memory as way too many people don't understand all the don't know about manufacturing tolerances and the effect headspace has in reloading and tuning a rifle and ammo.

For such a simple concept, it sure causes a ton of ruckus trying to define it.

Luck

The surplus rifle article is pretty good, but I disagree with his write up of excessive head space and insufficient head space. Head space, again, is a defined measurement for all cartridges..either the head space is right or it is wrong. Now an incorrect size cartridge can give you false ideas about either "excessive head space" and "insufficient head space"...if the original head space of the chamber is correct.

Jeffeosso; That is a very good link, easier to understand than some babble typed by some moron.

The confusion lies in the use of datum points for measurement. As an example both New york and Cleveland are located relative to the zero merridian. But they are 500 miles apart.
If headspace is not the space at the head of the case, what is it?.
Good Luck!

quote:

Originally posted by hawkins:
The confusion lies in the use of datum points for measurement. As an example both New york and Cleveland are located relative to the zero merridian. But they are 500 miles apart.
If headspace is not the space at the head of the case, what is it?.
Good Luck!

It's the specified length of the chamber for the specified cartridge to insure a safe proper fit.

Hawkins,

Actually the term head space is incomplete...it's called chamber head space.

Headspace is the distance from the casehead to the boltface in a loaded and closed weapon. End of discussion.

Later on some buerocrats decided to standardise, how incompetent sparepartexchangers could check this . In some european countries they started the standardising under CIP. In USA they formed SAAMI.

Remember that there is a lot of calibers that never has ben standardised under anny organisation. Therefor there is nothing like gauges.

However the gauges is a werry practical tool to make chambers so they can function with most factoryloads.


The lack of quality in the link Jeffersoe posted is clarified by the following:

quote:

Insufficient Headspace


Insufficient headspace prevents the closing of the bolt and possibly the complete chambering of the cartridge. If the bolt is forced this can cause the bullet to be compressed further into the neck of the cartridge's case. This will lead to over pressure conditions when the cartridge is fired and may cause very similar results as excessive headspace; the case may rupture sending very hot, high pressure gases through the rear of the receiver. Sounds like fun?

It totally shows that the author doesn't have a clue about what is headspace, and what is incuficient freebore, or neck clearence

Dam, this is really getting good!

quote:

Originally posted by jørgen:
Headspace is the distance from the casehead to the boltface in a loaded and closed weapon. End of discussion.

Later on some buerocrats decided to standardise, how incompetent sparepartexchangers could check this . In some european countries they started the standardising under CIP. In USA they formed SAAMI.

Remember that there is a lot of calibers that never has ben standardised under anny organisation. Therefor there is nothing like gauges.

However the gauges is a werry practical tool to make chambers so they can function with most factoryloads.


The lack of quality in the link Jeffersoe posted is clarified by the following:

quote:

Insufficient Headspace


Insufficient headspace prevents the closing of the bolt and possibly the complete chambering of the cartridge. If the bolt is forced this can cause the bullet to be compressed further into the neck of the cartridge's case. This will lead to over pressure conditions when the cartridge is fired and may cause very similar results as excessive headspace; the case may rupture sending very hot, high pressure gases through the rear of the receiver. Sounds like fun?

It totally shows that the author doesn't have a clue about what is headspace, and what is incuficient freebore, or neck clearence

jørgen,

The real expert here, swheeler, is so qualified he can at will call others morons.

quote:

Originally posted by SmokinJ:

quote:

Originally posted by jørgen:
Headspace is the distance from the casehead to the boltface in a loaded and closed weapon. End of discussion.

Later on some buerocrats decided to standardise, how incompetent sparepartexchangers could check this . In some european countries they started the standardising under CIP. In USA they formed SAAMI.

Remember that there is a lot of calibers that never has ben standardised under anny organisation. Therefor there is nothing like gauges.

However the gauges is a werry practical tool to make chambers so they can function with most factoryloads.


The lack of quality in the link Jeffersoe posted is clarified by the following:

quote:

Insufficient Headspace


Insufficient headspace prevents the closing of the bolt and possibly the complete chambering of the cartridge. If the bolt is forced this can cause the bullet to be compressed further into the neck of the cartridge's case. This will lead to over pressure conditions when the cartridge is fired and may cause very similar results as excessive headspace; the case may rupture sending very hot, high pressure gases through the rear of the receiver. Sounds like fun?

It totally shows that the author doesn't have a clue about what is headspace, and what is incuficient freebore, or neck clearence

jørgen,

The real expert here, swheeler, is so qualified he can at will call others morons.

Just you Moron.

swheeler, the resident drunk, adds a lot of knowledge to this topic and to the forum.

This started when I suggested that the Headspace on on old italian rifle could be
checked by adding layers of "scotch" tape to thre cartridge face. It will measure the headspace with that brass in that chamber.
This brought them out of the woodwork. It was
obious that understanding was lacking.
It still is.
Good luck!

Hawkins,
Are you playing the fool on purpose?

How many Barrels have you chambered? How about how many cartridges designed, including gauges?

You are talking about an artifact of actual headspace. If you took two different brass, unfired, and one fired but not resized, you would likely get three different measurements, assuming the tape didn't crush. And none of them would give you headspace

The distance from breech to datum is headspace. It doesn't matter if there is brass in the chamber or not. You many be able to measure something, but it is not the gunsmithing term headspace

Hawkins,

Cartridge cases are made to a minimum/maximum dimension with the maximum being under the specification to insure they fit all chambers. Some chambers are tighter then others, but this should only be in the diameters, as hopefully the lengths (head space) should all be the same. The idea of tape or shims used with the case in the chamber to see if the excess clearance is dangerous or not.

http://elephant.elehost.com/Ab..._men___elephant.html

The bolt closes, rhe chamber gets dark and in the mind the light goes out, and the datum is not a line, it is a round hole, the circle/round hold for the 30/06 is 3/8" in diameter or .375.

In the real world when someone tells me there is a datum line etc., I ask "How bout them Ka-boys and Ka-ree"? and I like the song by Don Williams 'AMANDA' and they do not have a clue.

F. Guffey

quote:

Originally posted by F. Guffey:
http://elephant.elehost.com/Ab..._men___elephant.html

The bolt closes, rhe chamber gets dark and in the mind the light goes out, and the datum is not a line, it is a round hole, the circle/round hold for the 30/06 is 3/8" in diameter or .375.

In the real world when someone tells me there is a datum line etc., I ask "How bout them Ka-boys and Ka-ree"? and I like the song by Don Williams 'AMANDA' and they do not have a clue.

F. Guffey

quote:

Originally posted by jeffeosso:
Hawkins,
Are you playing the fool on purpose?

How many Barrels have you chambered? How about how many cartridges designed, including gauges?

You are talking about an artifact of actual headspace. If you took two different brass, unfired, and one fired but not resized, you would likely get three different measurements, assuming the tape didn't crush. And none of them would give you headspace

The distance from breech to datum is headspace. It doesn't matter if there is brass in the chamber or not. You many be able to measure something, but it is not the gunsmithing term headspace

quote:

Vendor Supplied Information

Every gunsmith knows that proper use of a headspace gage is the most reliable way to test the length of a rifle chamber. "Headspace" is the distance between the face of the breech and the base of the cartridge when the action is closed, and excessive headspace can be dangerous as well as impair accuracy. For instance, unsupported brass fired in a rifle action with excessive headspace can rupture, allowing gas to blow rearward like a rocket exhaust. Because your safety is on the line, Forster Headspace Gages are made with painstaking care and exacting manufacturing standards to ensure accurate testing of your rifle's chamber.

Forster Precision Products
310 E. Lanark Avenue
Lanark, Illinois 61046
Phone: (815) 493-6360
Fax: (815) 493-2371

Hi Jeffeosso
Dont get to carried away trying to explain differently as manny in the buisness has done for ages
With your aproach to headspace, there would be extremely short cartridges demanded to fit in chambers made by smiths with headspaces under 1/1000"

Lets see how well I understand this.

Head-space, regardless of how it's measured is used to set a standard (of length?) for a specific cartridge.

Go/No-Go gauges are used to determine if a specific chamber is within specs. You can't use cartridge brass to determine head-space because for all you know the brass is already out of spec. For sure it will vary to some degree. In fact you could just as easily do the exact same test and call it a measurement of head-space of the brass as opposed to the chamber. The commonly accepted tool for proper and accurate head-space measurement is the above mentioned Go/No-go gauge.

When a gun smith checks head-space he isn't determining a measurement but rather ensuring that the chamber in question is within specs or that it falls within a minimum and maximum range.

Chambers and new unfired brass and cartridges are built to specs such that they never fall outside this range of accepted variation.

If your chamber is too tight or brass too large you can't close the bolt and therefore can't fire your firearm. If the chamber is too large, or brass too small, you can fire with the very real possibility of disastrous consequences.

A person without a set of gauges could fire a cartridge in the chamber and with measuring tools take accurate measurements of the fired cartridge and compare those to SAAMI measurements. Those can be misleading though as all brass expands tight against the chamber walls during firing then shrinks back.

Proper understanding of head-space with respect to datum lines and just where and how measurements are taken is really irrelevant to practical field measurements of finished products.

And I thought headspace had to do with the sizing of a hat..

I thought it was in reference to some lyrics in a David Allen Coe song?