When a chronograph is reading between two eyes,a lot of things can happen.Let me try to explain it in a simple way.Let's say the distance between the two eyes is exactly 12".When the first eye sees the bullet and the second eye sees it is exactly 12",you with have an accurate reading.Let's say you have a bullet actually traveling 3000fps and the eye is not properly picking up the bullet at the right time,it could be like 11 15\16" giving you that high velocity reading.Just a fraction being off at 3000fps is going to give you a false reading.I learned this one morning at the range.The way it was set up I was shooting east towards a rising sun.I start early one morning recording my velocities with the sun still behind the 30ft berm.About one hour later those same loads and rifles were shooting nearly 100fps difference.WTF???I was noticing a lot of variation from trip to trip with load velocity,so I decided to try something different.There was another section of range where you can shoot towards the North.My velocity readings began to be really consistent from trip to trip and my ProChrono is reading nearly the exact reading as my Magnetospeed.My conclusion to what was originally going on was the sunlight was casting a shadow on the eye boxes on my chronograph.As the sun rose higher my readings were changing too.Shooting at the other range to to North,the sunlight was not affecting my reading and they stayed the same because the eyes were seeing the light the same.My load for 160gr Accubonds with Reloader 22 is 66.0grs.I have four 7mags and all of them will shoot that load very well.There is a velocity difference between each rifle,shows that every rifle is different.The velocity range is between 3000 and 3100fps.
