Had I known this years ago when the only primers available were small magnum pistol I'd have bought them anyway. Some gun counter a-hole told me that you would have to lower your powder charge by a grain to make up for the "pressure"...and I believed him. Ack.
Prior to reading the above, I was told and under the impression that the safe procedure was to lower the powder charge by a half grain and work your way up watching for pressure signs.