Looks like there is a wide range of powders (in terms of burn rates) that will work in the 7mag...H4350, RL22, H1000, Retumbo.
If it was me, I would stay with the Hodgdon powders as they are most temp stable.
Here's a good resource for reloading data: 284_4_168
A great resource to have is the Hodgdon burn rate chart. It includes burn rates for almost all powders whether Hodgdon makes them or not.