Head Space and me!

C7AR15 · July 15, 2013, 06:03 PM

I have been shooting a long time (1970s) and reloading.

When I reload I do all the usual steps and then some --trying to squeeze more accuracy from my gun and loads.
This would include brass trimming, trickle charge to .1 gr. and seating .015" off the lands and on and on.

So where does headspace come into play when assembling my loads??
I know I can get headspace gauges but how will this change anything in my reloads???

Any Benchrest guys out there who know how to use headspace info to improve my reloads?

Awaiting your reply Thanks JD

jepp2 · July 15, 2013, 06:22 PM

How do you set up your resizing dies without some way to measure the shoulder setback you are creating?

I view the measurement of headspace more associated with proper case sizing. That can have an impact on accuracy, but I am more interested in not creating the potential for a case head separation due to excessive shoulder setback when FL sizing.

Jim243 · July 15, 2013, 07:07 PM

Quote:

So where does headspace come into play when assembling my loads??

In setting up your resizing die. I use these to insure correct head space.

Jim

steve4102 · July 16, 2013, 07:22 AM

You can use a gauge like the one above, or you can use a Stoney-Point (Hornady) gauge like this one.

http://www.youtube.com/watch?v=P-UrMTyJ1_E

You can also set up your FL die the old fashioned way without a gauge like this.

1. Put the Shell Holder in the press and raise the ram.

2. Screw the Full Length(FL) Die into the press so it is about a "nickle's thickness" above the Shell Holder.

3. Lube a "Fired" case (walls and inside the neck) and size it.

4. Remove the Lube and try closing the bolt on it in the chamber.

5. If the bolt closes with no resistance, screw the FL Die into the press about 1/8-1/4 turn and repeat steps 3 & 4.

6. As you feel the resistance begin, slow down how much you screw the FL Die into the press so you are at about 1/16 of a turn, or "Fine Tuning". At some point you will not be able to close the bolt and you are extremely close to having the FL Die in the proper position.

NOTE: The reason for this is because the FL Die has begun Resizing the Case-walls down to the Pressure Ring. As it does so, the Case-body lengthens slightly which in turn moves the Case-shoulder slightly forward. Then as the "Fine Tuning" continues the Case-shoulder makes contact with the FL Die and is moved slightly reward(or slightly shortens the Case-head to Case-shoulder dimension).

7. Stop when there is a slight bit of resistance when closing the bolt on the empty case. You now have a "slight crush fit" for the case in that specific chamber, or Zero Headspace.

8. Once you get it where you want it, take some masking tape or a black marker and put a Witness Mark where the FL Die Lock Ring is positioned to hold the FL Die in this position. Loosen the FL Die and return the Lock Ring to align with the Witness Mark and sung up the Set-Screw.
Screw the FL Die back into the press and try sizing another case. It should have the same resistance as the previous one. If not, you need to re-adjust the Lock Ring so it does. But you are extremely close to where you want it, so make very small changes at this point.
Occasionally check the fit of the cases in the chamber.

higgite · July 16, 2013, 08:43 AM

FWIW, I've sent back two Precision Mics because they didn't zero on a go gauge as they should have. One measured +.002", the other -.002". When I measured a fired case with a comparator that had been "zeroed" with a go gauge, it measured +.001" compared to the go gauge. So, I just set the shoulder back by .002", measured with the comparator. You can, if you want, use a Precision Mic as a comparator, but I already had a Hornady comparator and didn't need an inaccurate headspace gauge, so the PMs went back to the seller.
(Edit: I'm referring to .308 Win Precision Mics that I've had. I do have a .223 Rem PM that is spot on.)

Steve's method also works well with no measuring tools at all, but what can I say? I'm an engineer and NEED to measure stuff.

Bart B. · July 16, 2013, 08:55 AM

A crush fit means the case shoulder's set back a thousandth or two and that's not zero head space. "Zero headspace" is a term often used, but not exactly correct. "Head clearance" is the space between the case head and bolt face when the case stops going forward as it stops against the headspace point in the chamber. When there's a crush fit of the case in the chamber, then head clearance is zero.

I discourage folks from setting their full length sizing die so sized cases have a crush fit in the chamber. Doing this means there's a bit of binding of the bolt face against the case head. As virtually all factory rifles' bolt faces are not square with the chamber axis, depending on how a sized case is indexed, the amount of binding will vary. And the bolt will not close back into the same position for every cartridge loaded. Accuracy will suffer.

When benchresters neck only sized their fired cases, after 3 or 4 times the case would fit the chamber tight enough to cause binding. Accuracy got less. They full length size their cases, or at least bumped the fired case shoulder back a thousandth or two so the bolt would close easily without binding and be in the same position locked up every time.

If best accuracy's not your objective, then go ahead and get a crush fit.

July 15, 2013, 06:03 PM	#1
C7AR15 Senior Member Join Date: April 24, 2011 Location: Burnaby Posts: 260	Head Space and me! I have been shooting a long time (1970s) and reloading. When I reload I do all the usual steps and then some --trying to squeeze more accuracy from my gun and loads. This would include brass trimming, trickle charge to .1 gr. and seating .015" off the lands and on and on. So where does headspace come into play when assembling my loads?? I know I can get headspace gauges but how will this change anything in my reloads??? Any Benchrest guys out there who know how to use headspace info to improve my reloads? Awaiting your reply Thanks JD

July 15, 2013, 06:22 PM	#2
jepp2 Senior Member Join Date: December 24, 2008 Location: Loveland, CO Posts: 1,476	How do you set up your resizing dies without some way to measure the shoulder setback you are creating? I view the measurement of headspace more associated with proper case sizing. That can have an impact on accuracy, but I am more interested in not creating the potential for a case head separation due to excessive shoulder setback when FL sizing. __________________ NRA Benefactor Life member

July 16, 2013, 07:22 AM	#4
steve4102 Senior Member Join Date: December 23, 2005 Location: Minnesota Posts: 2,955	You can use a gauge like the one above, or you can use a Stoney-Point (Hornady) gauge like this one. http://www.youtube.com/watch?v=P-UrMTyJ1_E You can also set up your FL die the old fashioned way without a gauge like this. 1. Put the Shell Holder in the press and raise the ram. 2. Screw the Full Length(FL) Die into the press so it is about a "nickle's thickness" above the Shell Holder. 3. Lube a "Fired" case (walls and inside the neck) and size it. 4. Remove the Lube and try closing the bolt on it in the chamber. 5. If the bolt closes with no resistance, screw the FL Die into the press about 1/8-1/4 turn and repeat steps 3 & 4. 6. As you feel the resistance begin, slow down how much you screw the FL Die into the press so you are at about 1/16 of a turn, or "Fine Tuning". At some point you will not be able to close the bolt and you are extremely close to having the FL Die in the proper position. NOTE: The reason for this is because the FL Die has begun Resizing the Case-walls down to the Pressure Ring. As it does so, the Case-body lengthens slightly which in turn moves the Case-shoulder slightly forward. Then as the "Fine Tuning" continues the Case-shoulder makes contact with the FL Die and is moved slightly reward(or slightly shortens the Case-head to Case-shoulder dimension). 7. Stop when there is a slight bit of resistance when closing the bolt on the empty case. You now have a "slight crush fit" for the case in that specific chamber, or Zero Headspace. 8. Once you get it where you want it, take some masking tape or a black marker and put a Witness Mark where the FL Die Lock Ring is positioned to hold the FL Die in this position. Loosen the FL Die and return the Lock Ring to align with the Witness Mark and sung up the Set-Screw. Screw the FL Die back into the press and try sizing another case. It should have the same resistance as the previous one. If not, you need to re-adjust the Lock Ring so it does. But you are extremely close to where you want it, so make very small changes at this point. Occasionally check the fit of the cases in the chamber.

July 16, 2013, 08:43 AM	#5
higgite Senior Member Join Date: October 21, 2010 Posts: 1,025	FWIW, I've sent back two Precision Mics because they didn't zero on a go gauge as they should have. One measured +.002", the other -.002". When I measured a fired case with a comparator that had been "zeroed" with a go gauge, it measured +.001" compared to the go gauge. So, I just set the shoulder back by .002", measured with the comparator. You can, if you want, use a Precision Mic as a comparator, but I already had a Hornady comparator and didn't need an inaccurate headspace gauge, so the PMs went back to the seller. (Edit: I'm referring to .308 Win Precision Mics that I've had. I do have a .223 Rem PM that is spot on.) Steve's method also works well with no measuring tools at all, but what can I say? I'm an engineer and NEED to measure stuff.

July 16, 2013, 08:55 AM	#6
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	A crush fit means the case shoulder's set back a thousandth or two and that's not zero head space. "Zero headspace" is a term often used, but not exactly correct. "Head clearance" is the space between the case head and bolt face when the case stops going forward as it stops against the headspace point in the chamber. When there's a crush fit of the case in the chamber, then head clearance is zero. I discourage folks from setting their full length sizing die so sized cases have a crush fit in the chamber. Doing this means there's a bit of binding of the bolt face against the case head. As virtually all factory rifles' bolt faces are not square with the chamber axis, depending on how a sized case is indexed, the amount of binding will vary. And the bolt will not close back into the same position for every cartridge loaded. Accuracy will suffer. When benchresters neck only sized their fired cases, after 3 or 4 times the case would fit the chamber tight enough to cause binding. Accuracy got less. They full length size their cases, or at least bumped the fired case shoulder back a thousandth or two so the bolt would close easily without binding and be in the same position locked up every time. If best accuracy's not your objective, then go ahead and get a crush fit.