I have been handloading for years and have always accepted the Loading Manual's velocities as correct. This year I bought an Alpha Chrony, and am finding quite a variation in these velocities. My 8mm Mag is right where the Nosler manual says lit should be, my buddies .300 wm is 150 fps slow, my .338wm is right on with the 225 gr, but 250 fps slow with the 250 gr., my .223 right on. Can anybody explain this to me. Thanks-Karl