In most cases, unless you are already at the maximum recommended load or your loads have not already shown signs of excessive pressure you should be fine. Many of my load manuals have the exact same loads listed for a certain bullet weight with the only difference being some use a standard primer and some use a magnum. With my handguns loads, I routinely substitute magnum primers when tweaking a load for accuracy. Again, as with all new components, the key is to start low and work up.