I've been working up loads for the 40g v-max and had the same thing with pressure signs on the primers. I then studied and tried using the same primers that hodgdon book had listed and no more flat primers they had the fed 205ms listed. I,m using 28.5g bl-c(2) oal @ 2.250 trim to 1.850 Hornady cases. Hope this helps.
By the way the smallest group I've seen is around .350"