Weighing Powder Charges

I read with interest Annie & Stuarts post mentioning their use of a automated
powder measuring system i.e. RCBS Chargemaster. Like most BR shooters I've been using
a Harrell measure with nice fine powders like BM1, 2 or 2219 with pretty repeatable charges.
However, I've just started shooting F-class Std. and started using the way chunkier 2208 or 2208H
in my 308W but just can't seem to get consistent powder charges. Even at 300m vertical was evident and
a chrono session confirmed some fairly bad velocity spreads. As a control round I chrono'ed some British ex-mil 7.62
ammo that had less variation than my handloads ( what a shame job!)
I tried a Redding 3BR powder measure as well, almost as good as a Harrell but still inconsistant.
I guess the question to the F-classers out there is do you weight every load I throw and reject the light/heavy ones?

tnx, Chris