Headspace on the mouth questions?
- Thread starter mattri
- Start date
Fast14riot
Gold $$ Contributor
No, often the chamber has more room for growing brass than should be allowed for safe headspace at the datum.
Are you, for example, referring to a 45 ACP?
Fast14riot
Gold $$ Contributor
No, I assumed bottle neck, non belted or rimmed cases.
Sorry. I meant to send that to the OP.
Fast14riot
Gold $$ Contributor
Either way, clarification was needed from both myself and the OP.
I'm confused also. -------------- Are you talking Head space as in head space GAUGE ??
I'm not sure either what you are asking...headspace is a size designated and measured at different points depending on the cartridge/chamber. In terms of those that do in fact headspace on the mouth then it may not be correct to say headspace "is nominally the same as case overall length"....but that is at least where you would measure the case. In it's simplest form, headspace is really the difference between your chamber length and your case length. There is typically a range that you have to be within. So, in your scenario, lets say that minimum headspace length is 1.234" and the range or "tolerance" is +.004" -.000" {as typical} You have a minimum headspace chamber which is 1.234" and your cases measure 1.232" then you have .002" headspace, which is within the range or tolerance so you are safe.
I don't know what it is that you are really asking, so I don't really know if this did it or not or what else to say, except maybe....what exactly is your question??????? I will say this, you have come to the right place!!!! So ask away.
Fast14riot
Gold $$ Contributor
Maybe an article from today's bulletin might help clear some nomenclature up for the OP?
http://bulletin.accurateshooter.com/2017/02/understanding-headspace-what-you-need-to-know/
http://bulletin.accurateshooter.com/2017/02/understanding-headspace-what-you-need-to-know/
yes
Correct, referring to straight walled non rimmed cases such as the 45 ACP etc.
As illustrated here:
http://yaffa-cdn.s3.amazonaws.com/shooting/images/dmImage/StandardImage/headspace_diagram.jpg
As illustrated here:
http://yaffa-cdn.s3.amazonaws.com/shooting/images/dmImage/StandardImage/headspace_diagram.jpg
Alinwa is correct since a 45 ACP head spaces on the mouth. Keeping in mind there is a difference between cartridge head space and chamber head space.
No, that is the chamber length. Headspace would be the difference of the measurements 1.234 minus anything less than 1.234. If you can chamber case 1.234 and you cannot chamber and drop slide on case 1.239 then headspace for that cartridge case in same chamber would be anywhere from .000 to .004 of an inch , in other words a case for that chamber could measure anywhere from 1.234 to 1.238, if case 1.238 still will not allow the slide to close then headspace could be between .000 and .003 and so on and on . On the 1911 45 acp. the extractor holds the case when short cases are chambered that do not have sufficient length in order that their primers will be impacted enough by the firing pin to fire correctly.
No, that extra length between the case and the chamber is excess space. (free space)
The headspace is defined by SAAMI as the distance from the bolt face to the point in the chamber where the mouth of the cartridge is supposed to rest. (for a rimless case without a shoulder)
See the chamber drawings here:
http://saami.org/specifications_and...wnload/Z299-3_ANSI-SAAMI _CFPandR.pdf#page=10
The headspace is defined by SAAMI as the distance from the bolt face to the point in the chamber where the mouth of the cartridge is supposed to rest. (for a rimless case without a shoulder)
See the chamber drawings here:
http://saami.org/specifications_and...wnload/Z299-3_ANSI-SAAMI _CFPandR.pdf#page=10
Excellent replies, thanks to all.
So in our example a chamber is cut so that at 1.234" there is a "stop" or an "edge" that will prevent a case longer than that measurement from chambering on a closed bolt. A case that measure 1.239 (as mentioned above) would be too long, the bolt will not close properly.
On the other hand a case that measures 1.233" from base to front of case mouth in theory should chamber.
Getting closer?
So in our example a chamber is cut so that at 1.234" there is a "stop" or an "edge" that will prevent a case longer than that measurement from chambering on a closed bolt. A case that measure 1.239 (as mentioned above) would be too long, the bolt will not close properly.
On the other hand a case that measures 1.233" from base to front of case mouth in theory should chamber.
Getting closer?
Headspace on the case mouth
Go to SAAMI and study the 45 acp drawing of loaded rounds and the chamber. Check the measurments. http://www.saami.org/specifications_and_information/index.cfm?page=CC
Its possible with a custom short chambered 45 acp barrel, for the headspace be the same measurement as the brass. But not normal in a factory 45 acp.
The headspace is almost, 99% of the time , longer then the brass.
The 45 acp brass, seems to never need trimming, as the length gets shorter on firing target loads. I have never trimmed a 45 acp in 50 years.
From SAAMI
Go to SAAMI and study the 45 acp drawing of loaded rounds and the chamber. Check the measurments. http://www.saami.org/specifications_and_information/index.cfm?page=CC
Its possible with a custom short chambered 45 acp barrel, for the headspace be the same measurement as the brass. But not normal in a factory 45 acp.
The headspace is almost, 99% of the time , longer then the brass.
The 45 acp brass, seems to never need trimming, as the length gets shorter on firing target loads. I have never trimmed a 45 acp in 50 years.
Last edited:
Yes, You got it now....wanna say that SAMMI is saying the same thing we are saying but we are inserting a cartridge case into the equation which necessitates our definition, degree of forward and aft movement of the case in the chamber with the bolt closed can also be referred to as headspace in my opinion. Usually when a shooter refers to headspace when reloading it is this definition we use. Non bottleneck (some strait wall case's ) achieve their headspace by seating the bullet just so far off the lands ie: 45 acp 1911. Rimmed strait wall cases ie: 44 Rem Mag revolvers have zero headspace according to our reloaders definition as their rims are supported by the cylinder body, although there is space so the cylinder can rotate freely which could be referred to as a kind of headspace relevant to the movement of the loaded round within the cylinder. Lots of variables but correct headspace is a critical spec. for accuracy and safety.
I understand "head space" to be the distance between the breech face and some point on the case per Brownells. http://www.brownells.com/.aspx/lid=12555/GunTechdetail/Headspace-Gauges-And-How-To-Use-Them-Part-I
All cartridges and guns have these two components, even revolvers, though a revolver will also have cylinder to breech face gap.
For all firearms, if there was zero head space or cylinder gap, any tiny spec of dirt would cause the breech to not close or in the case of a revolver, the cylinder not to rotate.
All cartridges and guns have these two components, even revolvers, though a revolver will also have cylinder to breech face gap.
For all firearms, if there was zero head space or cylinder gap, any tiny spec of dirt would cause the breech to not close or in the case of a revolver, the cylinder not to rotate.
Head space is a chamber dimension. It has nothing to do with a cartridge. (other than limiting the cartridge length if it is to fit in the chamber)
Calling head clearance "head space" is like using the word "blue" to describe the color "red". You can do it but knowledgeable people will not necessarily understand the use or agree with your personal definition. It is better to use the words that actually mean what you are trying to express.
Calling head clearance "head space" is like using the word "blue" to describe the color "red". You can do it but knowledgeable people will not necessarily understand the use or agree with your personal definition. It is better to use the words that actually mean what you are trying to express.
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.