My cast bullets when the mould is up to temperature are very consistent in weight. By average there are more in the pile that weigh exactly the same then the other pile that is 4/10's from light to the heavy end so I don't weigh them anymore.
I save the cold mould bullets and throw them in a coffee can and those get used for the swaged bullets and when I run them through the swage dies I adjust the core swage die so it swages the core about 5 gr lighter than the cast bullet this will fill the wrinkles and like Sharps said there will be some weight difference between 0 and 3/10's in the core weight. You also have to be consistent swaging the bullet like you do casting the bullet. It takes so long for the lead to bleed through the bleed off hole in the swage die to get the exact weight if you want it but the core will be with out voids unlike a cast bullet can be.
You can double or triple raise the ran when you swage and this will get the core exactly the same weight. I can take a swaged bullet that weighs 8-10 grains more that came out of the swage die as long as the core fully blead off and I will see the same impact down range on paper. This much weight difference makes no difference with a swaged bullet. This is something you cant do with a cast bullet with that much weight difference.
A hammer swaged bullet can vary in weight depending how close you cut the extruded lead wire or cast the core in weight but running the core through the hammer swage you will have weight differences but you will have a bullet with out voids and it will also be a consistent diameter and it will shoot well.
There are a lot of advantages swaging the bullets but a well cast bullet will shoot just as well as a well swaged bullet.
