Applescript: Finder set target to smart folder

If I try to open a Smarty-Folder using applescript it does not seem to work properly. It seems to open the right path, but not show any items, also you can see the file-tree at the very bottom (that you usually just see in normal directories)

tell application "Finder" to set target of front Finder window to POSIX file "/Users/stockholm/Documents/Useful-Files/Settings/Finder/Search-Project/Julian-In_Progress.savedSearch"

It works when I use open, but this does open it in a new window, which I do not want.

tell application "Finder" to open POSIX file "/Users/stockholm/Documents/Useful-Files/Settings/Finder/Search-Project/Julian-In_Progress.savedSearch"

Anyone an idea why this happens? Still very new to applescript, would appreciate your advice.

kind regards Julian