Try sizing them!
I've tried washing, weighing, sizing, lubeing & have decided after much testing that sizing is all that is needed to get consistency from pellets.
That is what works for me.
I use JSB 4.53 sized with a sizer (4.53) made by X2RED on Airgun Universe Forum CNC Stainless Steel about £15, I seem to remember. Well made accurate bit of kit.