Help for New Spring.

[airnutz]

Hello folks.

I read here in the Library about "Calculating Spring Space".  I will soon open my vintage Diana 35 up and replace the spring with an Original Export Spring.  Although I know it will fit, could someone explain in some detail on how to calculate the room?

I know this is done in the cocked position, and starting from the inside of the front side of the piston to the back plate of the spring holder (terminology?).

I do not comprehend how this is done. Anyone?

Thanks in advance.