Re: which 7mm
Go with the stw.I've had one in the stable for over 10 years and it's been very good to me. I've had the 7rum and currently own a 30rum, but the 7stw is in many ways better than both of the others. You can make brass from either of the holland cartridges, the 8mmrem, or the la weatherby rounds, so contrary to popular belief, good brass will always be around.
It has better case capacity than the 7-300 or mashburn, has a lot of good data for reloading, dies are common(not hundreds for the set), and it will go 2000 rounds on a good barrel if you don't beat it up(the 7rum will die before 1000 if you don't down-load it). There are other reasons too, like the fact that it is the smallest cartridge that will deliver 2000 foot pounds to 400 yards with full house hunting weight bullet rounds. The fact that you can shoot one prone without a brake on it; try that with a 8.5# 300u-- you'll be getting stitches and the 7rum would be close.