What are the effects of varying base to datum lengths

Tac-O

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Apr 28, 2019
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Sandy, UT
I was prepping some once fired Hornady brass for my kids' gun last night and noticed that I had a spread of 0.005" for my base to datum measurements on the brass for 20 cases. I've not had that issue with that die before and it's usually only a 0.001 or 0.002 spread. I guess that lot of Hornady cases sucks for hardness consistency.

I'm wondering if anyone has done any testing on the effects of varying amounts of headspace with their handloads?

Would there be a drastic difference in velocities? A noticeable effect on accuracy?
 

swampbug

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Oct 26, 2020
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Dallas
Once fired brass may or may not have expanded to the full chamber size. Generally not .
Assuming your .005 spread was caused by some cases being shorter, the above would explain why. New cases are generally shorter and take a couple of firing to expand to a rifles chamber.
There would not be drastic differences in velocity or accuracy with .005 spread but consistency is the goal.
A .002 "bump" is what most handloaders use. It provides a good chamber fit and can still easily run the bolt.
 
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Tac-O

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Apr 28, 2019
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Sandy, UT
Once fired brass may or may not have expanded to the full chamber size. Generally not .
Assuming your .005 spread was caused by some cases being shorter, the above would explain why. New cases are generally shorter and take a couple of firing to expand to a rifles chamber.
There would not be drastic differences in velocity or accuracy with .005 spread but consistency is the goal.
A .002 "bump" is what most handloaders use. It provides a good chamber fit and can still easily run the bolt.

It's good to know it won't make drastic changes to either parameter. I always bump my brass for my own gun about 0.003 and I have the die for their gun set up to bump about the same and it's been consistent until this batch. I have primarily just been reloading Hornady brass for them after they shoot hornadys reduced recoil cartridges. I would guess they may have all started with varying lengths and maybe have some varying hardness too.
 

Tiny Tim

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If they are from reduced recoil loads, its likely they never fully expanded to the chamber. Any chance you measured prior to resizing, or have any cases not resized yet to compare to?
 

Tac-O

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If they are from reduced recoil loads, its likely they never fully expanded to the chamber. Any chance you measured prior to resizing, or have any cases not resized yet to compare to?

I have before and they were relatively consistent, but that was just for the first box. I have another box I've not resized yet so I'll check those out.
 

Tiny Tim

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Jan 26, 2015
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I have before and they were relatively consistent, but that was just for the first box. I have another box I've not resized yet so I'll check those out.
Could just be this lot of brass causing inconsistencies. I wouldn't worry about .005 variation unless shooting 500+ yards if everything else is consistent.
 

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