I've loaded HS-6 with 115g 9mm and it works well enough. But's better suited for my 5" Barretta than my 3.5" Kahr. If your 9mm is a compact, I'd recommend a faster powder - like 231 - at least for 115g's. It has a burn rate that is probably better suited for 124g bullets, however. If I loaded 124's, I'd definitely give HS-6 a whirl.
The main reason why I have HS-6 is for medium powered .357 and .44 rounds. And it works particularly well for 38+P, and hot rounds for my 1911 .45.
Overall, I like HS-6. Versatile.
If you ever find yourself in a fair fight, it's because your tactics suck." -- Allen West, quoting Marine 1st Sgt Jim Reinfinger