I am new to reloading.  I recently purchased some measurement tools from Hornady including a headspace gauge that attaches to my calipers.  I am not sure how to use this data.  

- Do I want my brass to have uniform headspace?  Is this achieved by bump sizing?

- Is HS measurements an indicator that my brass is reaching end of its serviceable life?

Yes, exactly!



You will find that attempting to push the shoulder back by 0.001 will result in no sizing happening whatsoever. Brass is springy, until the pressure in the spring gets up towards 58K PSI the brass will return to the previous size and shape. By the time you are pushing them back by 0.0015 you have enough pressure in the die so the brass flows and sizing happens. If you want to size brass by 0.001, but the case up in the die, raise the ram and cam it over, then hit the sizing die with a rubber mallet once or twice.



Which is why some of us Neck Only size most of the time.

Great info guys.  Thanks very much.  I have not bump sized any brass as of yet.  Just to confirm, I use the FL sizing die backed out to bump size?  Also how do I know when and how much to bump the shoulder down?  After 2x firings or more?  To determine the desired HS.  Should I measure the headspace of a new, unfired case and bump the fired case shoulder down to the new case size?   Or use a one fired / fire formed case for the desired HS.

Thanks again for the help.

Take a factory round and fire it from your gun. That will cause the brass to expand to fit your chamber

Use your new headspace gauge to measure the shoulder of that brass. Write that number down. 

Then you'll want to adjust your resizing die so when you run the case through the die, and remeasure, the new headspace number is .002 less than the 'fire formed' case. 

This tell you that you've bumped the shoulder just enough to not over work but enough to be reliable and chamber safely. 

Test 5-10 cases to make sure you're getting accurate measurements. Both on fire formed dimensions and your resize dimensions. 

This can take some trial and error. Start with your die 'loose' and slowly turn it down, while running the case thru the die, until you get the correct measurement

To answer your questions in your original post. Yes you want your brass to have consistent headspace after resizing. No it doesn't correlate to lifespan of the brass