This has been ask before. Many think that the only way to improve
the 300 RUM is to neck it up to 338. The 300 RUM is so big with low
body taper and a fairly sharp shoulder, that there is little increase
in case capacity to be gained. I think it's just right the way it is.
What I'm looking for is a higher bc bullet. There is much more to
be gained there than by a slight increase in velocity. When that 220 grain
bc=0.9+ bullet comes along, I'm going to have a 300 RUM built that will
handle that much bullet. I'm wanting to take a feral pig at one mile.
The 300 will do it but the bullet is more important than the case design.