I'm new into reloading and would like to know what kind of poder is best for large rifles such as a 7mm stw? Do you get faster speeds out of fast burning pwder or do you want a slow burning powder. I plan on shooting a 140 accubond out of a 24.5 inch barrel?

Your best source of info for such matters is a reloading manual, in fact, several of them. Check their velocity figures for the 140 gr bullet and I think you'll find that the higher velocities come from slower burning powders. And, you might just find, when all is said and done, that the 140 gr Accubond isn't the bullet your particular barrel likes best, so prepare to be a little flexible.

I have owned three 7mmstws and still own two.My rifles all shot best with 140gr ballistic tips and imr 7828 but yours may not.I will however recommend the federal 215 primer.With every rifle it will take some trial and error to develop a load.However,I can tell you not to expect more than 3400fps with a 24.5" barrel.