For these scales that have a check weight, how heavy is the weight? And what is the usual range of the scales? Do the scales have an "auto calibrate" of sorts for use with the check weight? Or do you just check the accuracy at that point and then send it back to the manufacturer for complete calibration if it's off? I just have a hard time believing that you can get any kind of a decent calibration done on a scale by checking accuracy on only a single point in its range, unless of course that single point happens to be the same weight as your charge.
Tried that. The disparity in volume between one grain and one gram makes converting pretty much a no-go.
.