That will vary depending on what powder you're using. Some powders have better metering characteristics in a sliding disk type measure like the Dillon and the Lee. Small charges, using flake powders (like 3-ish grains of Clays) are rather inconsistent; I get a few squibs with this stuff, though no over-charges. Extra-fine ball powders tend to leak out, too, and are somewhat inconsistent; to the tune of +/- 0.4 grains or so (thinking H-110 here). Powders like Titegroup and lil-gun - smaller than flakes, but not ultra-fine like 110 - ten to meter very well, I'd guess that 90% of the charges come in at +/- 0.1 grains, and the remaining 10% are within +/- 0.2 grains. I've never tried stick-type powders like Varget or 4350; all my rifle loads get weighed