RE: Information on the 7mm ultra mag and 300 ultra mag
First off, I would go with the .300 RUM due to popularity over the 7mm RUM. More availibility of loads and components.
As for recoil, it is not for the recoil sensitive at all. You didn't say what you currently shoot but if you are very comfortable with 30-06 recoil then you should be able to handle the .300 RUM. The RUM will be quite stiffer than an '06. If an '06 is close to your threshold, then I would try before I bought.