I don't think it was intended to bring higher velocities generally--you're right-- but in my 284, the one I've really tested, I worked up loads for the 140-gr TTSX and the 150-TTSX with both R17 and H4350. In both cases (no pun) I got about 150-175 fps more with the former. I worked up to slightly flattened primers and a hint of an ejector mark with both. This brought me to 3100 fps with the 140 and 2975 with the 150 with R17. I then backed down a 1.5 grains until I sat at a hair under 3000 fps for the 140 and right at 2900 fps for the 150. With H4350 I had the flattened primers and ejector marks about 150 fps short of those final velocities with R17. Same primers of course, same COL, etc.
This increase with R17 over H4350 may just be a quirk with my rifle or even a quirk with that powder lot or may not be. Of that I'm not sure but those are pretty good speeds for the 284 case and those bullet weights. I do have a 23" tube.
