Here is what I found for the 7MM STW
All the data they are using federal 215 primers, 29"barrel, H1000 powder, all are using 162gr Amax
75gr @ 3049fps
76.5gr @ 3114fps
78gr @ 3192fps
79gr @ 3254fps
81gr @ 3322fps
I would start out some where around 74gr of H1000 and work up
Powders to consider, H4831SC, H1000, Retumbo. I use to shoot a regular 7MM and I loved it. I use to have a sendero 300RUM but had to get rid of is as I just could not handle packing that beast around, my gunsmith found a guy who had a 280AI and wanted a 300RUM. It is a custom 280AI and it shoots great, its light and hardly any recoil to it. Keep us informed. Good luck