Very well described!
The patch does get very hard, and stable. I size it to .001 over groove.
My mix is either pure wheel weight, water dropped, or 50/50 with 2%zinc.
The castings with the patch size right down. In time, if they have not been loaded, they do grow .001. I have 50 I have been too lazy to load that grew that much.
I have probably by now done several thousand this way. I love it. I have fully loaded the magazine with the patched loads. No issues there.
I do not crimp, I just use the Lee FCD to tension the neck.
I get real good confetti on firing.