I agree with HunterJim, when changing a component you should reduce then work back up to the predetermined charge if your were close to peak pressures or max loads in the past. Starting from scratch it doesn't matter, as you should be working up anyway.
MQ32, it certainly is possible for a primer switch to yield better results with everything else remaining the same. If loading a LR primer I start with WLR's. I have found in some cases the Fed 210GMM's produce better results, like in my 270/150NP load. When dealing with a magnum primers I use 215GMM's. These are the three primers I keep on hand and haven't had any problems finding loads with them. Trail and error is the only way, as what works for me may not work for you.