Factory ammo was pre-magnetospeed.
What I have concluded is that what I thought was an optimum load, probably isnt. I chronographed to see why some of the groups were poor after sticking to what I believed was a good load. I assumed it would be related to inconsistent velocities etc. It does not seem that way.
I’m going to look at the load again and once decided upon a reliable OCW I will stick with it and just use the chrono to fine tune the load without making too much of a fuss about exact group size. Once I have chosen the load with a good velocity, low SD and ES I will check the final result without anything else added to the barrel.
I think I may have made a bad call at the first stage and have struggled since. A morning at Bisley should resolve this once and for all!