Which measurement to use for full length resizing?

[SleepDoc]

I fired 98 factory hornady 6.5 cm 140-eld-m's and after measuring them all today I am confused what I should set my resizing die to. The rifle is a GAP bolt action and planned on resizing them 0.001" down from fired headspace but I have such different headspace measurements. The cases were all measured with a hornady headspace gauge on my calipers.

2 were 1.5285"
18 were 1.5290"
24 were 1.5295"
35 were 1.5300"
8 were 1.5305"
7 were 1.5310"
4 were 1.5315"

So do I pick the measurement from which I had the most of?

 

[FLIGHT762]

Did you remember to decap the fired primers in the cases before measuring?

 

[Fursniper]

Did you remember to decap the fired primers in the cases before measuring?

Excellent question, and the answer is.............?

 

[SleepDoc]

Yes, were decaped and tumbled before measuring

 

[NukeMMC]

I would size to 1.528-1.529"

 

[Fursniper]

Hummmm I'm scratching my head on that one....something is not right there. My variation from case to case is only half a thousandth. Short stroking the ram on the press maybe? How many rounds on the brass, ie, the springback looks to be quite different, are you annealing? Annealing will give you a constant rate and more consistancy.

 

[padom]

What calipers are you using? Are you spinning the case to make sure it's square in the jaws of the calipers?

I would bump them back to 1.5275" and load them up. You will be good. I typically bump back .0015-.002

 

[SleepDoc]

Hummmm I'm scratching my head on that one....something is not right there. My variation from case to case is only half a thousandth. Short stroking the ram on the press maybe? How many rounds on the brass, ie, the springback looks to be quite different, are you annealing? Annealing will give you a constant rate and more consistancy.

They are once fired never reloaded. They were factory loaded 140 eld-m

 

[Sheldon N]

Since this was the first firing some of the cases may not be fully blown out to chamber dimensions. That would lead me towards bumping back from the longer dimension cases rather than basing off the shorter cases.

To confirm, I would also double check the feel on bolt close after sizing. Measure diameter at the base and just below the shoulder to make sure you've got adequate body sizing from your die, then pull your firing pin spring and ejector plunger so you can feel bolt close on a piece of sized brass. I like to size to the point where there's just a tiny bit of feel when closing the bolt, just before the bolt falls freely with no effort. Once you've got that number then stick with it. This video helps show it...

https://youtu.be/WfWS7R1CdZI

 

[Milo 2.5]

Since this was the first firing some of the cases may not be fully blown out to chamber dimensions. That would lead me towards bumping back from the longer dimension cases rather than basing off the shorter cases.

To confirm, I would also double check the feel on bolt close after sizing. Measure diameter at the base and just below the shoulder to make sure you've got adequate body sizing from your die, then pull your firing pin spring and ejector plunger so you can feel bolt close on a piece of sized brass. I like to size to the point where there's just a tiny bit of feel when closing the bolt, just before the bolt falls freely with no effort. Once you've got that number then stick with it. This video helps show it...

https://youtu.be/WfWS7R1CdZI

Take this advice^^^^