"I backed the die of 1/2 turn and it seated just fine. Should I back off the die until I find the point at which the case will no longer seat in the action? "

IF those cases were originally fired in your rifle, you should be able to put them back in the chamber and close the bolt without having to size them at all! If this is the situation, then I'd set my die to just resize about the first 2/3 of the case NECK to hold the bullet firmly when seated. (You won't get incosistent shoulders unless your expander button is hard to drag back out of the case. If you don't lube up the inside of the case necks somewhat, this can happen, and it can pull the shoulder forward some. I use powdered graphite or "Motor Mica" as a dry lubricant for the inside of case necks.

In any case, set your die to WORK THE CASE BRASS AS LITTLE AS POSSIBLE. So, whenusing brass fired in some other rifle, if you back the die off to where a case will not allow the bolt to be closed, then screw it back in SLOWLY until the bolt just locks up, that will work the brass the least, and this should help increase the life of the brass.

However, you do want it sized downmore for hunting ammo! I generally hunt with Ruger single shot rifles. For these, I want the cases sized to where the completed round will fall freely into the chamber with the muzzle pointed down to a depth that allows the block to close without having to push on the cartridge head, and then the round must slip back out when I raise the muzzle and lower the block! Ammo made like this always works in the field.