OS OK I'll have to ask my buddy what his weight intervals were but I seem to remember 1 grain. BTW if you catch yourself looking through the sights for over like 7 seconds without taking the shot stop and start over again. That bull is no longer where it looks like it is, its burned into your retina. BTW with respect to "the thin line of white" I do have one buddy that does it that way but he has 20/15 vision, the big front aperture is what a lot of us do, I did not want to do it at first as it seems like a bad idea but my other buddy forced me to do it one day and I never went back, my groups shrunk markedly. Whatever size you choose make sure the bull is round and black when you look through the aperture, too small an aperture will make the bull look egg shaped and gray.