If your chamber is inspected by the Smith, then the above is where I would go.
Also for the guys who bushing neck size, my Redding die only necks about 80% and the area at the neck/shoulder junction is larger by some factor. My premise is, quicker sealing near the neck shoulder is one positive piece in many factors. Mandrel sizers work great too, so it leaves the other problems in the discussion
However you go about it, the neck must slam open into the chamber, primer must be igniting a larger portion of the powder, neck tension must resist the forward movement against primer detonation, resulting in the brass to seal in the chamber neck.
FWIW, I only get soot to the area on the neck where the bushing die stops sizing, at that 80% line. I only have .004 neck clearance for a clean bullet release.
Annealing certainly does complete the fire forming process, especially on the belted mags with .020 shoulder space on first firing. In your case, if headspace is not consistent after firing, that is also a problem, as you are setting your dies to a moving target. All fired cases at the shoulder datum line should be within .0005- not more than .001.