This from RCBS FAQ
Q. I'm having trouble with the Hand Priming Tool not seating the primer deep enough. What am I doing wrong?
A. You probably aren't doing anything wrong. The usual cause for "high" primers is caused by the shell holder not sitting down tight on the Primer Feed. This usually happens with older RCBS and other brands of shell holders--they simply do not have enough chamfer on the inside of the primer hole. To check to see if this is a problem, install the shell holder on the primer feed. If you see any daylight between the bottom of the shell holder and the primer feed, the shell holder must be replaced. If the shell holder was manufactured by RCBS, call for a free replacement. If you are unable to locate the problem, call RCBS Customer Service for help at 800-533-5000 (Mon-Thurs, 6:30am-3:00 pm Pacific time), or e-mail us your questions.
Hobie