I’ve found bluecast to have a variable shrinkage rate, depending on environment and time from print to investment. In the summer, I was losing 1 ring size from the original model to the cast piece. In winter, that went down to half-a-size. However, I get these results only if I print, rinse/dry/repeat 3 times, and then invest on the same day - preferably right away.
If I leave a print for a day or two - even in a drawer or dark cupboard, there’s a noticeable shrinkage.
I now only use bluecast for models where precision isn’t totally required - like pendants without gem settings, or prototype models. For anything else, I go back to formlabs castable. (I’ve found by properly curing my prints, using R&R Plasticast - finally available in the UK - drying my invested flasks overnight at 20°C and holding the oven initially during burnout at 143°C for 2 hours, I’m getting great, non-porous results).