Seem's to me the directions with dies have said to cam over for years. I suspect with a tight chamber it is needed, I did it myself for years. and doing that will resize any case to fit pretty much any rifle. Problem came in for me years ago shooting a 7mm Rem Mag. Had a sloppy chamber, lot of belted cartridges and rimed cartridges had that problem. Then following the direction actually allowed the case to fit all rifles but the sloppy chamber contributed to case head separation. That is when I learned about partial sizing. The deal is even with chamber's for rimless cases the chamber in each rifle can vary a bit. But even with the variance the case will still work in the chamber of most rifles. The ones then that separate the head are said to have excessive head space Th chamber is actually out f spec. It can be fixed by moving the barrel back and rechambering or can usually be fixed with partial sizing. In partial sizing the die goes down to the shell holder also but then is backed off. Then the die goes down only far enough to allow the case to fit properly in the to long chamber. But, you can size the suggested way and the ammo will normally still fire in that long chamber but case life will be decreased. That rifle you just did probably has a tight chamber but is SAMMI spec. To neck size with the FL die, the die doesn't touch the shellholder but is taken down to where you can see it stops on the case before touching the neck. Problem with that is that you'll fire a couple rounds and have to FL the case to get it to chamber again. Problem being, if you call it a problem, is your chamber is a bit longer than SAMMI Spec but still falls within it! By partial sizing you simply resize the case to fit the chamber of that gun.
I have two 243's and I partial size both. One rifle will shoot the ammo loaded for either rifle but the other rifle won't. Nothing wrong with the ammo, just the cases sized to fit individual chamber's. One chamber is tight and one not but both are within Spec. The theory behind making the case fit an individual chamber is that it better lines up the bullet with the bore, I don't know that for a fact but maybe it does. I do it out oh habit left over from trying to make a hunting rifle a match rifle!
