As many have stated, it's best to back off a minimum of 1 grain powder with this switch. My process is to chrono the current load while observing case characteristics. Then using chrono shooting the magnum primer loads while documenting case pressure characteristics with velocities. Some guns really take to the magnum primer swap while others seem to not like it. A lot of this is attributed to fundamental frequency (Natural frequency) of the rifle. I have been able to shorten a barrel up in an effort to drive faster velocities and Accuracy. In short treat it as a test firing for new load development. Take care and hope this helps.