6mm Rem Improved Brass Length

[rcw3]

I am working with someone on a 6mm Rem Improved project. With a 6mm Rem Improved, the question is what was the overall length of the brass when you started and what it typically becomes after you fire form it? I assume when it is fireformed the case becomes slightly shorter, but I don't have any handle on how much it typically shortens.

Any info would be a help.

Robert Whitley