I have an early 5906 with non Novak fixed sights. We have all heard the "rule" that model 10s, 36s, etc. have thier sights regulated for 158gr. bullets. Is there such a "rule" for S&W 9mm? 115, 124, or 147gr? I tend to shoot a little low with 115 and 124gr bullets, however my nephew shoots dead on, so maybe it is just me. We both shoot at the same POA. with Hi Powers and I'll be darned if I can figure out what I am doing wrong with the 5906.