1) is this repeated consistent variation noted with use of a chrony?
2) with different loads of .5 grains I would expect some variations;
3) are these variation reproducible at will?

Personally I don't believe that small change has all that big an effect on typical range target distances.
Also in the past, it seemed I had more variation with the lighter charges as well.

One of the most consistent recipes I've found, was with Trail Boss, which also gives a more gentle 'poooosh' for recoil.

IIRC, those charges are pretty low in the ballistic chart. It's been a while since I've ran that recipe combination so can't compare with my own results.

It may do your recovery better by going to smaller calibers for the duration. I've had to recover from dislocated shoulder enough to recognize just how pleasant taking a 'stick with 22s-for-a-while vacation' can be.

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