Bob72, “What play?” I have been told Lee seater dies are most accurate? A seater die does not offer case body support, I suggest you attempt dropping a case into the seater die before installing in the press, if any alignment is done it will be above the shell holder at the opening of the die. Any seater die can be used with a dial indicator on top of the die, all my seater dies are used with universal type indicators, the seater plug stem protrudes above the die, if it protrudes I can measure it with a height gage, depth micrometer or a dial caliper, all I am required to do is be able to index it or .000/zero the indicator, the fact the threads are not 20 per inch does not hang me up.
I have (2) RCBS Gold Medal and Competition seater dies, the best feature is the ability of the die to center the bullet in the case mouth, I have made a few bullet seaters that do not use die bodies but offer shoulder and neck support, seating can be accomplished with an old bottle capper of aluminum can crusher.
F. Guffey