I believe you mean the case is being damaged during bullet seating!!?? IF SO, my guess is that your die is trying to apply a crimp to the case when there' s no cannelure (crimping groove) on the bullet under the case neck. If so, the case brass has no place to go when the die tries to crimp it, and the case collapses at the neck/shoulder junction. This effectively ruins the case, and it won' t chamber!!

To test if this is what is happening, put any empty case into the shell holder, and raise the ram to push the case up into the die. You will feel the point where the crimping shoulder stops the case travel BEFORE IT GETS TO THE TOP OF THE STROKE!!??

IF THIS IS WHAT IS HAPPENING, JUST BACK OUT THE SEATING DIE A TURN OR TWO, TO THE POINT THAT THE CRIMPING SHOULDER IN THE DIE NO LONGER TOUCHES THE CASE WHEN THE RAM IS ALL THE WAY UP!! TEST THIS BY RUNNING AN EMPTY CASE INTO THE DIE. IT MUST ENTER FREELY, WITHOUT TOUCHING ANYTHING WHEN ALL THE WAY IN THE DIE. THEN SCREW THE BULLET SEATING STEM DOWN TO THE POINT WHERE IT SEATS THE BULLET TO THE DEPTH YOU WANT!! This same thing happened to me when I started reloading, WAY back in 1954!! Ruined several .30/' 06 cases before it dawned on me what was happening!!