1. Different ingredients make different cakes.
2. Heat removes hardness strength from lead alloys; shot strings, ambient temp, aging and drawing/annealing by heating and cooling will lower BHN of a lead alloy.
3. Depends. It will eliminate shearing and tearing and deformation, the same way sizing after lubing the conventional way will. Accuracy will still have greater suck potential if the check is sized out of alignment....
4. Not for the powder coat.
5. Yes, just like jacketed bullets can be driven faster without leading.
6. Accumulation of leading decreases accuracy, as does poor fit. Like I said before, some people jack up fit so bad by either sizing or loading even loads that don't lead can shoot like crap.

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Five softnosed 22 Hornets that chronied at 2,900 fps without powder coating.

Its best to fix the outcome and hedge bets before powder is dumped, or, if people gave as much attention to bullets as to dumping powder, most other minor ills will go unnoticed.

Don't turn darts into boomerangs....