Re: 7mm Rem Accumark Load Testing
I would say that you can not tell much from one 3 shot group of any particular powder charge. Too small a sample. Could be the load, could be wind, could be you, could be seating depth, could be a number of things.
Now if you repeat this whole experiment 3 times and get more data. Then you will have a better idea of what is going on. But this is an expensive exercise and is wearing out your barrel.
With "big cartridges", I have given up on this process due to the large number of shots involved. I now forget about accuracy and just work out where my maximum charge weight is. Then back off 1 grain and play about for an accurate load by adjusting seating depth.
If I can not find an accurate load at this charge weight by adjusting seating depth, I then back off the powder charge by 1 grain, and try again, starting with using the most accurate seating depth from the higher powder charge.
scientia est potentia