For those who have the old style Lee Loader and don't like to tap with a mallet to seat the primer, I found a method that works well.
I braced the table of my small Black&Decker drill press with a chunk of 4x4 , then tightened down a piece of steel tubing in the chuck.
Placing the primer seating cup on a slabl of steel laid on the table I just pushed the casehead down around the primer by using the advancement handles as a lever. Primers seated smoothly and evenly.
I have one of the Lee side lever type loading outfits, plus a set of Herter's dies for the .303, but I prefer the older Lee Loader.
The Lyman Nutcracker has them all beat.