This probably should go on the "reloading" board so if it disappears, look there for it.

Any time you change a component, you "can" see a difference. Case thickness, hotter primers (like Magnums), ball powder to extruded, etc can all effect a number of things, including pressures. Not many people can predict what will happen unless they've made the exact change that you're talking about. Even then, chamber tolerances (lack of consistency) can eliminate even that.

Whenever you make a change in your components, start from scratch and work your way back up. That's the only safe way to do it.