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I just have not had any issue with runout and nose sizing, but, I am only sizing down about .001 on the nose. They are an interference fit in the bore, which is what I wanted.
If serious about it then get a mold made for a bore rider with the nose section reduced. Accurate will do that for you. You can request the nose section to be small enough that the PC coated bullet will chamber. No extra charge either.
There were some cast bullet shooters who made special dies for final sizing. Basically a swage die that 'sized' the entire bullet. Had reduced section for the nose. They would apply the gas checks, size and lube as normal, then put the bullet into the final die. The initial idea was due to out of round bullets, but, it applies to this as well.
I do like your approach with the punched out pad.
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The post below shows a clear PC boolit I have it sized .0025 over. I cylcled it in my 336's action. You can clearly see the groves. I size after PC so there is not a variance in thickness between boolit diameters. It shoots extremely accurate. My favorite gun to shoot cast in!
https://i.imgur.com/YDWVlg6.jpg