If the shaft has been tapered to 5/16, it's probably too small for self-nocks. How do you grind your nock, point tapers? I use a self made jig set at 11 degrees which I use on my table saw equipped with a sanding disk. Just put a few thicknesses of masking tape near the nock taper end to account for the thinner shaft there due to the tapering, and then nock taper as I normally do. If you have a woodchuck tapering tool with a sanding disk, a few pieces of masking tape in the groove closest to the sanding disk might do the trick. Good luck.