This is a 7mm WSM built on a long action. COAL is 3.050 .010 off the lands with a Berger 180. I worked up with H1000 and H4831SC until I got less than .5 moa. I have shot 5 three shot groups with 66gr H4831SC in the .3 moa. Here is my problem/concern, four of the 3 shot groups had an extreme spread of less than 10 within the group the fifth had an extreme of 18. The total extreme spread of all groups is 100fps. If I remove the two groups shot with new brass the extreme spread drops to 40fps. All the groups were shot on different days in near identical conditions. I am finding it hard to believe statistically that my chrono is telling the truth. I would find it easier to believe if my extreme spreads within a group were 40fps and group to group extreme spread was more consistent. My next step is to continue taking chrono data and start moving out in distance while noting vertical dispersion as well as checking point of impact against my ballistics app. I would like to hear your thoughts.