I'm not sure if you can drop your own powder charge in the 650 or not. So this may be off topic.
I've been using the DPS 1200 for my charges. It has the capability of perfect accuracy each time but the software prevents it so you can expect +/1 0.10 grain deviations.
Initially I'll throw a charge a few grains short, then trickle up on a scale and powder trickler. Once I'm satisfied a few grains either way doesn't effect the harmonic, I don't worry about it and just throw the charge.
This is for match ammo. For the regular stuff I just use the one that came with the Dillon.