Getting a little low on std large rifle primers and they are not on the shelf in most places.
I have a tendency to load towards the upper end. If I substitute mag primers for std. would their be a great tendency for significant pressure increases? 270's; 7mm 08's etc.

Rule of thumb is to drop back one grain of powder if you substitute a mag primer for a standard. I see no harm in going back 1-1/2 grains and starting over, but you probably won't notice the difference if you reduce by one grain and go.