twadsw01
Well-Known Member
Please enlighten as to how me knowing the definition of headspace would alter my concerns in this particular case, scooter. Is there anything to be concerned about or not, in your opinion?
Nonsensical Headspace Measurements on 223rem cases...??
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http://www.saami.org/specifications_and_information/index.cfm See the Glossy for definitions. You should put Scooterbum on your ignore list, as i just did.
Basic - Sized brass must let the bolt close fully when chambered.
If the brass shoulder is set back more then .010" , when compared to the chamber, a case separation can happen.
Your brass has not fully expanded to the chamber. It takes about 3 firings of neck sized brass.
Basic - Sized brass must let the bolt close fully when chambered.
If the brass shoulder is set back more then .010" , when compared to the chamber, a case separation can happen.
Your brass has not fully expanded to the chamber. It takes about 3 firings of neck sized brass.
twadsw01
Well-Known Member
Thanks, 243.
Unprepped sizes being super consistent isn't an indication that the brass expanded to the chamber? I don't understand.
Unprepped sizes being super consistent isn't an indication that the brass expanded to the chamber? I don't understand.
twadsw01
Well-Known Member
Ok, looked up headspace. So is there an official name/word then for the dimension we are measuring when measuring from case head to shoulder datum?
Photos i made just for guys like Mr. ScooterBum. 
Then there are others that say "Chamber Headspace" and " Cartridge Headspace"
This comparator thing has been online many times. https://www.brownells.com/aspx/learn/learndetail.aspx?lid=11470
Then there are others that say "Chamber Headspace" and " Cartridge Headspace"
This comparator thing has been online many times. https://www.brownells.com/aspx/learn/learndetail.aspx?lid=11470
twadsw01
Well-Known Member
Wow, thanks for the education. Still reading the Brownells link. That is really novel info, for me.
So, the follow-up data I posted suggested that on average I was setting the shoulder back from a fired cartridge 3/1000"; this sounds like the number I should be focusing on, correct, 243?
So, the follow-up data I posted suggested that on average I was setting the shoulder back from a fired cartridge 3/1000"; this sounds like the number I should be focusing on, correct, 243?
Cartridge Head to datum is good. Maximum listed by SAAMI is 1.4666" - .007" tolerance.
At the SAAMI link, look at the 223 rem cartridge drawing and the chamber drawing.
The chamber drawing has the head to datum measurement marked as "Headspace"
twadsw01
Well-Known Member
Ah ok. I get it, I believe. The Hornady tool I'm using isn't measuring from the breech face, so this it isn't capturing true "headspace"
Lonewolf74
Well-Known Member
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I don't believe you have anything to worry about with your cases. I do my 223 ammo on a Dillon 550 and it's just the nature of the press to have some variance.
I first set my die up to bump the shoulder back .003 which caused a lot of variance, about +- .005 or more from case to case. And occasionally a case shoulder gets pulled out causing a long measurement. This is generally caused by a lube issue. If you use spray lubes and or don't lube inside and outside of necks you will encounter this shoulder pull out, probably already have and is the reason for your variance.
After some frustration I turned my sizing die down to where it makes good contact with the shell plate (turn down to touching shell plate then 1/8 turn more). This sizes my brass about .009 which is more then I want but it keeps variance around +- .002 between sized cases which I can live with. I don't think you could get it any better on a progressive press.
All my serious ammo is made on a single stage press which is much easier to keep variance to +-.001.
I first set my die up to bump the shoulder back .003 which caused a lot of variance, about +- .005 or more from case to case. And occasionally a case shoulder gets pulled out causing a long measurement. This is generally caused by a lube issue. If you use spray lubes and or don't lube inside and outside of necks you will encounter this shoulder pull out, probably already have and is the reason for your variance.
After some frustration I turned my sizing die down to where it makes good contact with the shell plate (turn down to touching shell plate then 1/8 turn more). This sizes my brass about .009 which is more then I want but it keeps variance around +- .002 between sized cases which I can live with. I don't think you could get it any better on a progressive press.
All my serious ammo is made on a single stage press which is much easier to keep variance to +-.001.
twadsw01
Well-Known Member
Alright. All of this is for non-precision stuff anyway, so the variances don't really bother me that much. Just wanted to make sure I wasn't overworking my brass or putting myself at risk of head separation.
In my early days, 1979 , with no comparator or cartridge gauge, the Dillon shell plate gave me .014" shoulder set back and case separations in my M16A1 carbine.
But only at the 1 station when the FL die was adjusted to make contact.
But only at the 1 station when the FL die was adjusted to make contact.
Mikecr
Well-Known Member
None of the last measures matter, as they are still NEW cases, Right?
That is, they're yet to be fire formed in your chamber.
That is, they're yet to be fire formed in your chamber.
bigedp51
Well-Known Member
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- Dec 10, 2010
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- 1,022
twadsw01
What make and type dies are you using? Dillon dies are small base dies and reduce case diameter even more than standard dies.
When you full length resize it is possible to make the case longer in cartridge headspace length than its fired length. This is because the case is squeezed inward and the brass can only move upward in the die.JP Enterprise
You just need to measure a few fired cases from your chamber and then adjust the die to bump the shoulder back .003 to .006 for a semi-auto.
Below a Colt Field gauge at1.4736
Below the same Colt gauge in my adjusted Hornady cartridge case headspace gauge.
Below a "fired" Lake City 5.56 case fired in my AR15, and I bump the shoulder back .003 shorter from this measurement.
Below are a Wilson, Dillon and JP Enterprise case gauges and not all case gauges have the same inside diameter. The JP Enterprise gauge inside diameter is smaller the the Wilson and Dillon gauges and is made with a chamber finish reamer. A case fired in a semi-auto should be .003 to .005 smaller in diameter than its fired diameter after sizing. This is to insure the case will spring back from the chamber walls and eject reliably.
I use the red JP Enterprise case gauge to check all my loaded rounds to ensure my reloads will fit in the three AR15 rifles I load for. Meaning I use the Hornady gauge for die adjustment and double check the loaded cartridge in a case gauge for diameter and headspace length.
All you need to do is bump the case shoulder back .003 to .006 from its fired length. And this depends on your die adjustment and how much brass spring back you have after sizing. And a case gauge checks to ensure the resized case is within acceptable shoulder location to chamber.
Bottom line check some factory loaded ammunition with your Hornady gauge against your resized cases. My resized cases are .002 longer than factory loaded Federal M193 with .003 head clearance.
What make and type dies are you using? Dillon dies are small base dies and reduce case diameter even more than standard dies.
When you full length resize it is possible to make the case longer in cartridge headspace length than its fired length. This is because the case is squeezed inward and the brass can only move upward in the die.JP Enterprise
You just need to measure a few fired cases from your chamber and then adjust the die to bump the shoulder back .003 to .006 for a semi-auto.
Below a Colt Field gauge at1.4736
Below the same Colt gauge in my adjusted Hornady cartridge case headspace gauge.
Below a "fired" Lake City 5.56 case fired in my AR15, and I bump the shoulder back .003 shorter from this measurement.
Below are a Wilson, Dillon and JP Enterprise case gauges and not all case gauges have the same inside diameter. The JP Enterprise gauge inside diameter is smaller the the Wilson and Dillon gauges and is made with a chamber finish reamer. A case fired in a semi-auto should be .003 to .005 smaller in diameter than its fired diameter after sizing. This is to insure the case will spring back from the chamber walls and eject reliably.
I use the red JP Enterprise case gauge to check all my loaded rounds to ensure my reloads will fit in the three AR15 rifles I load for. Meaning I use the Hornady gauge for die adjustment and double check the loaded cartridge in a case gauge for diameter and headspace length.
All you need to do is bump the case shoulder back .003 to .006 from its fired length. And this depends on your die adjustment and how much brass spring back you have after sizing. And a case gauge checks to ensure the resized case is within acceptable shoulder location to chamber.
Bottom line check some factory loaded ammunition with your Hornady gauge against your resized cases. My resized cases are .002 longer than factory loaded Federal M193 with .003 head clearance.
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