I am a bit of a novice when it comes to having a custom rifle built and I have a design question. How do I determine the optimum OAL for a given bullet? Specifically, what is the optimum maximum OAL for a 300 RUM and 245 grain Berger? I think I want my bullet to just touch the lands at the maximum optimal length, so that I can work up a load with maximum powder capacity in the case. I do still need it to fit in the magazine but I do have an extended length magazine. I am having a bit of a hard time putting my question into words but hopefully that makes sense.