Time to cast,

[Don McDowell]

You can probably slide by with as much as a 3 grain spread if the bases are all good, and if the lube grooves are filled on a greaser.
But with good casting technique holding to a 1 gr spread, with .5 +- from the median weight , with the bulk of a run of 100 or so right on the median weight is pretty doable.
It will mostly come down to what gives you piece of mind when you're on the line and going for score. Confidence in your ammunition and knowing it's as good as it can be helps shoot better scores, providing the wind and mirage gods are going to allow that on any given day.