I will be honest with you. First I don't have a 300wby but in all the rounds I have loaded for the Fed primers have not been all that great for me ( my experience ) I did notice the match primers a little more consistent but varied with powder used. Some powders simply dont like some primers due to reasons unknown by me so I usually work up the same load with more than one primer type and most everytime there is one primer or the other that will be better with the powder I am trying to use. For instance I have found VihtaVouri powder doesn't like rem 91/2 primers at all but seems to like the magnum version better. There are no disadvantages or advantages I can list because I have no experience with that particular round so I would suggest trying them with the same powder and see which one actually produces the best results such as extreme spreads on velocity and group size at given distances.