Chk. your loaded round & see if it's contacting the rifling. Bullets have different ogive designs. Same weight but different style bullet could be contacting rifling higher up on ogive. I have a die that wouldn't fully size a case on a go-gauged chamber. As a last resort, you can sometimes add a piece of .002" scotch tape to the bottom of the go-gauge, re-HD SP then add a second layer of tape for the no-go. This may give you just enough extra room in the chamber to allow your die to work properly. I've had F/L dies that sized too short & one that sized not quite enough (.0015" too long) I'm beginning to think that out of spec dies aren't all that rare.