If your using large rifle primers in a load. Will the preasure change a lot if you change to large rifle magnum primers? I'm loading for the 500 smith & Wesson and I couldn't get What I wanted so I switch. Is this safe?

If your a max load now, I wouldn't do it. Its hard to say for the 460 and 500. They won't always show the traditional signs of pressure like a rifle will because they are not running at 60-65KPSI, but run around 50KPSI.

I have read a lot of article where mag primers jumped up preassure 3-4KPSI. One of the better ones was from precision shooting.