Tuners do allow you to load down a bit and maintain tune, rather than with powder/seating depth. Depending on you cartridge, tuners usually can make up for about 1.2-1.5 grains of powder within a given node...for lack of a better way of putting it. IOW, if there is 1.2gr between completely in tune to completely out of tune, that distance can be correlated to tuner marks. With MY tuner, the typical short range bbl is about 4 marks and the typical longer, long range bbl is about 5 marks from completely in and out of tune. You just break the powder charge down the same way, dividing by 4 or 5. The group shapes even repeat, respectively.