A few folks have convinced me there is a really good use of the Lee FCD, and that is to keep them from having to gauge every loaded round for the shooting games where a failure to feed or fire is significantly worse than whether the ammo is bullseye accurate. Lots of people use it this way. Their loads are plenty accurate enough and they never jam up the gun.
That said, yes, the reloader should take care to make sure the FCD isn't covering a mistake that can be remedied by adjustments. It should be there to iron out the occasional bullet that got seated a little crooked, or an over sized bullet causing a bulge, or a nicked up case etc.
Some folks like to use a case gauge, and some like to use the FCD. I always advise, if asked, that one learn without it, so they can catch mistakes and fine tune their reloading adjustments etc before adding the FCD to the mix.
That said, yes, the reloader should take care to make sure the FCD isn't covering a mistake that can be remedied by adjustments. It should be there to iron out the occasional bullet that got seated a little crooked, or an over sized bullet causing a bulge, or a nicked up case etc.
Some folks like to use a case gauge, and some like to use the FCD. I always advise, if asked, that one learn without it, so they can catch mistakes and fine tune their reloading adjustments etc before adding the FCD to the mix.