Primers
The small magnum pistol primer should give you the best results as there is a slight difference in the cup thickness between pistol and rifle primers.
As for the powder charges sometimes an adjustment will be necessary while at other times the same charge will work just as well. However due to the increased amount, and sometimes hotter burning primer mixtures found in some magnum primers, and if the loads you had been using were near maximum loads, backing off to a more moderate starting load would be the most prudent action, and slowly work up toward the powder charge you were using previously. At the first sign of excessive pressure, back off a couple of tenths.
However, in rare cases where the primer may be from a different manufacturer, it may be necessary to change powders to achieve the same degree of velocity and accuracy you were getting with the regular primer you were previously using.
F. Prefect