I would use .429" jacketed bullets, and .430" lead. Copper jacketed bullets take a lot more pressure to swage them into the rifling, and if you are .001" over bore already you're talking about some potential for serious pressure issues. Lead, being much softer, works well because will deform with much less pressure, and a slightly over bore diameter lead bullet seems to work better at sealing the bore and preventing gas cutting than a bore diameter.

I'm not familiar with Fastex, and I'm not personally a believer in the various snake oil bullet "lubricants". The fact is that, despite the coating, the bullet is still .001" over bore diameter, and the pressure necessary to squeeze the bullet into the bore is the same.

Mike