I have collet dies for 10 different calibers and this is the way I adjust all of them:
Run the lock collar up to the TOP of the threads
this will put the lever at the most horizontal when sizing
and makes it easier to gauge 25# on the lever
I also order undersized mandrels from Lee (only $5.00 ea but minimum order applies)
since I did not have good luck reducing the diameter by spinning against an abrasive (hard to get it reduced and still have it perfectly round and the exact same diameter from top to bottom of mandrel)