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Old March 26, 2009, 04:40 PM   #13
Bart B.
Senior Member
Join Date: February 15, 2009
Posts: 7,278
GuitarXM asks: What is the spring tension you are referring to? Is that the tension the press will place on the case after full length sizing, meaning case fully inside die and the die is touching the shell holder?
It's the amount the press top that holds the die pushes up from friction between the case and die as the ram goes up. With an empty die is adjusted to just touch the shell holder, when a lubed case is pushed up into the die all the way, the bottom of the die will be a few thousandths above the shell holder. This springiness is only in the vertical or die/case axis.

I've watched the die slowly come back down a tiny bit as the ram's still all the way up. That's just the spring pressure of the press pulling the die further back down the case.

"C" presses usually have more spring than "O" types as there's more metal holding the top part where the die's at. Lee hand loaders may have very little spring.

One really should use a gage to measure fired cases then again after sizing them. Otherwise, the actual amount of shoulder set back could be several thousandths off from what one wants to get. The amount and type of case lube plus any spring in the press will greatly effect the gage readings after sizing.
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