Measure the brass in question with the headspace comparator, and compare this measurement with the go-gauge measurement. This will tell you everything you need to know.

If the brass is indeed sized to far (shoulders bumped too much causing excessive working headspace) there is a way to salvage the brass. But it requires a fireforming technique with the bullets jammed hard in the lands. And preferably a faster burning powder like Varget or Benchmark and a load near the middle between the starting and max load, maybe more like 1/3rd of the way from minimum book recommendation just to be unquestionably safe.
This will form the brass with out thinning the brass above the case head.
Sometimes it requires fireforming more than once to get the shoulders as far as the chamber if the load is too mild.

Also a picture or link to one would be helpful for us to judge the brass in question.