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Take the die, complete with expander, out of the press and look up into the interior. Check if the stem is centred. Sometimes they're not but can be untightened, turned slightly until centred and...

I'm not sure either what that measurement should be. It needs to be small enough that the expander will open it up again, enough to allow bullet seating with some tension.
So now I'm guessing here...

Maybe, but if so I would think he would not be decapping cases either if it was that high. So, if successfully decapping the expander is probably positioned OK. But, if the expander is set too high...

Not much is necessary, only a thin film but it doesn't hurt to have a little too much which might just give you a safety margin initially. Cover the whole case body, but particularly the bottom...

The ring on the neck of the left case in both pics makes me wonder if it's been inserted far enough into the FL Die. When the FL Die is correctly set into the press that ring would be at or near the...