Spacey question

Lilswede1 · December 3, 2009, 09:34 PM

Would -.006 to .-010" headspace affect accuracy of a round?
If so, why?

Slamfire · December 3, 2009, 09:40 PM

Maybe for a bench rest rifle.

For someone using the bench for a rest, I doubt it.

In human held hands, no.

What you will find with the shoulder pushed .006 to .010 below SAAMI minimum, is something called case head separations!

You can take .006" case stretch as a rule of thumb for maximum stretch before case rupture.

F. Guffey · December 6, 2009, 12:50 PM

Again, Hatcher moved the shoulder forward on an 03 Springfield .125 to test a theory. It would appear the novel ideal of head space caused case head separation, though he did not take credit for his creation, after firing he removed cases from his modified chamber that were 30/06 + .125 or 30/06 Hatcher cases fire formed in his new creation, not 'oddly enough' nor consonantal, the same event is repeated when a 8mm57 is fired in an 8/06 chamber, the difference between the length of the case from the head of the case and shoulder of the two chambers is (+ or -) a very few thousands, when this accident? happens the shooter gets 8/06 cases with very short necks, not quite the same but there are other accidental chamberings as with the 308 W being fired in a 30/06 chamber, this results in a fire formed 30/06 case with no neck .

Always omitted, TIME, it takes time for the case to expand before the event gets serious, it all three events mentioned above the pressure increase was slowed by the case filling the chamber, I have fire formed cases for the 30 Gibbs with loads that would be close to maximum after forming.

As with .010 head space and new cases, once the case is fired and the shoulder moves out and forms to the chamber I apply the 'leaver policy' once it is out there I 'leaver there'

EXCEPT, I know where the shoulder of the chamber is before I size for loading, I form first then fire, with the exception of chambers like the 30 Gibbs, again the neck on the Gibbs is .218 long on most chambers, I could use Cylinder brass from R-P, cylinder brass is 2.260 long with out a shoulder, my kind of case, moving the shoulder forward is the difficult part for most, I start with a case that has a shoulder forward of where I want it then move it back with the 'companion tool' to the press. A case that is 2.650 with out a shoulder is a 'can not miss' case 'if one knows when to stop, something like a wo (stop) before the bang.

F. Guffey

December 3, 2009, 09:34 PM	#1
Lilswede1 Senior Member Join Date: September 8, 2008 Location: NW Wash State Posts: 216	Spacey question Would -.006 to .-010" headspace affect accuracy of a round? If so, why?

December 3, 2009, 09:40 PM	#2
Slamfire Senior Member Join Date: May 27, 2007 Posts: 5,261	Maybe for a bench rest rifle. For someone using the bench for a rest, I doubt it. In human held hands, no. What you will find with the shoulder pushed .006 to .010 below SAAMI minimum, is something called case head separations! You can take .006" case stretch as a rule of thumb for maximum stretch before case rupture.

December 6, 2009, 12:50 PM	#3
F. Guffey Senior Member Join Date: July 18, 2008 Posts: 7,249	Again, Hatcher moved the shoulder forward on an 03 Springfield .125 to test a theory. It would appear the novel ideal of head space caused case head separation, though he did not take credit for his creation, after firing he removed cases from his modified chamber that were 30/06 + .125 or 30/06 Hatcher cases fire formed in his new creation, not 'oddly enough' nor consonantal, the same event is repeated when a 8mm57 is fired in an 8/06 chamber, the difference between the length of the case from the head of the case and shoulder of the two chambers is (+ or -) a very few thousands, when this accident? happens the shooter gets 8/06 cases with very short necks, not quite the same but there are other accidental chamberings as with the 308 W being fired in a 30/06 chamber, this results in a fire formed 30/06 case with no neck . Always omitted, TIME, it takes time for the case to expand before the event gets serious, it all three events mentioned above the pressure increase was slowed by the case filling the chamber, I have fire formed cases for the 30 Gibbs with loads that would be close to maximum after forming. As with .010 head space and new cases, once the case is fired and the shoulder moves out and forms to the chamber I apply the 'leaver policy' once it is out there I 'leaver there' EXCEPT, I know where the shoulder of the chamber is before I size for loading, I form first then fire, with the exception of chambers like the 30 Gibbs, again the neck on the Gibbs is .218 long on most chambers, I could use Cylinder brass from R-P, cylinder brass is 2.260 long with out a shoulder, my kind of case, moving the shoulder forward is the difficult part for most, I start with a case that has a shoulder forward of where I want it then move it back with the 'companion tool' to the press. A case that is 2.650 with out a shoulder is a 'can not miss' case 'if one knows when to stop, something like a wo (stop) before the bang. F. Guffey