The burn curve with Longshot would make it a great candidate, and it always produces excellent performance in the 9mm, 9mm+P, 40 S&W, and 40 S&W+P I've tried, particularly with heavyweight bullets. I've had great luck with plated 220's in the 40, shooting them at about 1050 with Longshot. It's a heavy-spring load, for sure, but causes no wear and tear. Until I got a 200gr GCWFN mould, it was my bear load in an XD 5". I'd start with the powders Underwood uses. I doubt you'll get the top speed out of AA#9. It just isn't that energetic compared to Longshot, Power Pistol, Blue Dot, or 800x. You may get better accuracy though, and the push will be a bit gentler. As well, if #9 works, 2400 will also work.
