Bullets Age expanding?

[mtgrs737]

Yesterday I checked the diameter that my Star sizer was sizing to and was disapointed to see the the boolits were .0005" under the scribed size on the die. I was sizing some of Lee's 200 gr.SWC's cast just hours before of WW with 20% linotype. I was wondering if I should look into opening up the die to .453" in order to get my minimum .452" diameter sized boolit.

I got to thinking that I read on one of these threads where the hardness of some boolits changes over time, and also that there is some springback that can occur when a boolit is sized. So I picked up some of those same boolits and starting measuring with the same caliper as I used yesterday and every one of those boolits I measured made a fool of me. Every one measured .452" on the button!

I guess that the people that made that die knew what they were doing. :wink: :castmine:

[JSnover]

My ".459" boolits are sizing about the same way; half a thousandth under, after giving them a few hours to cool. They have to shrink a little in the beginning. After they set for a while and have time to age-harden or soften it wouldn't surprise me if the dimensions change a bit. They shoot well enough for now.
Was the shop temperature the same on both days, and were the bullets the same temperature both times? Do you have another caliper or a standard to verify the measurement, and are your tools kept at a fairly constant temperature? It all matters when you start measuring to (or beyond) the fourth decimal place.