The Redding bushing dies have a countersunk hole in the top of the die that you access by removing the decapping stem. You then just drop the right size bushing into the hole, and screw the decapping stem back into the die body. You figure the size of the bushing by measuring the loaded round, and then subtract the amount you want for bullet grip.
Example: Your loaded round measures .251" diameter on the neck, and you want .001" bullet grip (which is what I've found to be the most accurate most of the time) then you buy a .250 bushing. If you are ramming your ammo hard from the magazine into the chamber, you would probably want .002-.003" bullet grip so you would get a .248" or .249" bushing.
I always neck size until my ammo won't fit in the chamber anymore, then I just slightly bump the shoulder back about .001" with a body die. I very rarely use FL dies. I have found that they have a tendancy to make your loaded ammo somewhat out of round. Redding makes bushing neck dies, competition neck bushing dies, competition bushing FL dies, body (bump) dies, regular FL dies, and regular neck dies. Basically, anything that says competition on it has a micrometer on top and a floating sleeve. This is ideal, but I have loaded ammo with no runout using just the standard "S" bushing dies and a comp seater.
It might get confusing with the names of all these dies, but if you get lost, just look at
www.reddingreloading.com, or leave another post! The only dumb question is the one not asked! /ubbthreads/images/graemlins/wink.gif