Let me rephrase my question. Did you buy the 300 RUM for that purpose or decide to convert it from a gun you didn't care for?
I purposely bought a .300RUM in M70 because first it's a M70. The M70's just generally feel the best in my hands and I prefer the 3 position safety. I bought the 300RUM because it only takes a minor amount of work to make it work for a 404J. The RUM calibers have the same length action as the .404J.