Ehud you need to resize your brass after each firing, I would strongly recommend full length sizing to maintain case consistency.
The Wilson gage is more the size of your chamber and a lot of cases will drop into them even with minor issues or without being resized. It is checking for case overall length and head space length but not so much the body diameter. If you compare that to a Hornady gage your case un-sized will not drop in and may not drop in after resizing depending on your sizing die. It is checking the case for actual case dimensions as well as overall length and head space and is much tighter than the Wilson. Neither gage is bad you just need to understand what they are each doing,
If you are resizing brass to go back into the same chamber you have little to worry about. Set your shoulder back .002 -.003, check your overall length (trim if needed) and you will be fine.