by Hoot » Tue Jul 25, 2017 7:51 pm
Were those resultant case head growth numbers before or after resizing? They usually get a little narrower and a little longer after resizing. Now, if those dimensions are after resizing, you have about one more repeat of those 39gr loads before the cases will start binding in the chamber on the next reload. I'm guessing they were before resizing. You have a learning opportunity if you're up for it. Mark them and also measure the length. Wipe them off with a rag with a little mineral spirits or other mild solvent on it, dry them, lube and resize them. Then take the diameter and length measurements again.
All that having been said, You strive to keep the case head diameter growth to less than .005 increase that doesn't resize back at the most. Otherwise, you'll hit the diameter wall in about 4 reloads. Tamer loads don't cause such irreversible growth. I myself, do not reload 1st fired brass more than 4 times or for a total of 5 reloads. As their diameter grows, that metal has to come from somewhere and where it comes from is often less length length. Usually around 5 reloads, I hit the 1.685 length or .5015 diameter threshold which lands them in the "charity" peanut butter jar. I know bolt action enthusiasts don't have the same issues as the AR platform in this caliber.
Hoot
EDIT: Don't ever trim 450b cases.
In Theory, there is no difference between theory and practice. In Practice, there is.