Re: 338 RUM W/225 Cutting Edge
The new H-1000 could be faster than RE-25 now. I have not tried the new H-1000. But dropping three grains puts you at or a tad faster than re25. So I would definitely drop down to 99-100 grains to start with and maybe load one bullet at 99, 100, 101, 102 just to see what your max is going to be. Then you can go back and load some groups from there. I still have the old H-1000 so wouldn't know about the new stuff.
Predictions are difficult, especially when they involve the future