The "shrink factor" is something that is endemic to any cast material. If varies for each and every alloy and is something that also, to some extent, depend on the mould materials being used.
Liquid metal and solidified metal, depending on how it is "solidified" will not have the same volume.. Annealed material will not have the same dimensions as hardened and tempered. Simply put, metallurgy ain't that simple nor can it be simplified to that level.
Badically, you can not minimize the shrinkage - you can only account/compensate for it in your tooling and/or moulds when you size/construct them.
When you start to do post casting heat treating, you're into a whole new realm of shrinkage/distortion to learn and/or deal with.