1 Attachment(s)
Well at least I found the load development chart...
Made at 100 meters, off a sandsack, service sights
Attachment 102742
Note that it is statistically awkward to define the best. But easy to see the worst: loads that should be avoided.
Note also that, as the group size variation is almost certainly a resonance effect of the barrel whipping around, it will vary according to powder type, bullet form, weight, seating etc. In other words, you will have to determine it yourself, for your rifle.