Is the Norma brass new? If it is, back off two grains and fire form. Don't look for a load until you have fireformed brass to your chamber. Most brass is made short of chamber length so it will fit all chambers. Firing a maximum load with brass that is short for your chamber can overstretch not only the head diameter but also the body length. Start with 10 pieces of new brass and be aware of case length, case head diameter, and overall cartridge length. I would not continue using the brass that has loose pockets. Loose pockets create a poor gas seal. Escaping gases can damage bolt and trigger. Not worth it. On your question regarding seating length, I'd start at the cannelure for fire forming then go out further with test loads. Measure head diameter at the belt with a micrometer with .0001" resolution so you have an idea of pressure. Any expansion of more than .001" at the belt is not good. You should be under this number after fireforming. Generally after fire form you should have .0005-.0008" expansion at the belt.