Trying to track down the reason for an observation. That being whether a cartridge is FL sized or is measured as Fire Formed SOME cases show a variation in headspace as they are rotated within the guage. The gauge being a Redding Instant Indicator.
Its not consistent as some cases have no variation. Im guessing this is normal and its only come to light using the Instant Indicator. If I assume its normal then what sort of variation can I expect is acceptable. Im find ing anywhere between 0.0005 and 0.0015 variation can be seen at times. For my application this makes it very difficult to accurately punch out a bunch of cases that I have confidence in being uniform. Has anyone else observed this? Any comments or thoughts to add?

If they were all different the same way I'd say your die. However if the fired case all hadn't expanded to the same point then the FL die might not contact a specific point on the shoulder.

As to acceptable. You are spending time dealing with the issue of .0005 or .0015 you have too much time on your hands.

any tiny burr on the cartridge head will show up as it is passed over the primer relief area milled into the shell holder. .0005- .001 would be an extremely small skiff on the face of the case head. i use the hornady type h.s. gauge and rotate the case as i check for uniformity.

Half a thousandths!!!??? When you are dealing with a ductile brass pressure vessel that can vary as much as twenty times that. There are far more useful ways to spend time; this is not one of them. This is not, in any universe, a problem, issue, concern, or any other item to think about.

Clean the die and remove any excess lube in the shoulder area.

Wipe the lube from the neck and shoulder area before sizing.

Rotate the case 180 and size again.

And place your instant indicator on a higher shelf where you have trouble reaching it.

OR better yet, return it for a refund!

George

Fired brass may not fully expand to the chamber with 1 firing. Neck size or control shoulder bump till bolt is a little hard to close. Same as a crush fit.

FL sizing dies need to contact the shell holder to remove slop for press/linkage. To control how much you bump, while the die and shell holder are in contact, buy Reddings competition shell holder set.

George do you not like the redding instant indicator? it looks to me difficult to use but i've never had my hands on one.

Neck sizing is the way to go. use two firings, THEN set the shoulder back in future loadings until they chamber with no crush fit..IF YOU ARE USING THE LOADS TO HUNT WITH..Otherwise go with the crush fit until they won't fit anymore, then reset the die back to a crush fit trim the case more than likely and continue on.

I always use full length resized cases for big game hunting and particularly for Dangerous Game, and in most cases new cases reloaded.