Why are 180s the heaviest you would need? If you are wanting to shoot to 1k, a heavier more streamlined i.e. higher bc bullet would be better. If you are just wanting to shoot 180s and under, take a look at a 300 WSM
or SAUM. Either round will get you to 2950 with 180s without too much fuss. That would save you up to 10-15 grs of powder per boom.
If you are stuck on those three cases, the 300WM would be the best compromise. Top-notch brass from Lapua or Nosler with no fire-forming needed, and it is not a powder hog like the RUM.