Interesting thing about AA#9 using more powder, I did measure my 8.4 gr load of Longshot and noticed with the long 200 gr Noslers seated to 1.260" provides plenty good enough powder compression to prevent any bullet set back in the case, something I do for ALL SD rounds, whether semi auto handgun or rifle.
Point of clarification - AA9 doesn't necessarily use more powder by volume, but it is very dense, and uses more powder by weight. In the 180-220gr range, it's just about the perfect burn rate vs volume for 10mm, as it'll reach max pressure with a full charge but is hard to get enough powder in the case to go too far over pressure. Granted there's always "that guy", but if you aren't compressing it like crazy, that's how it's always worked out for me.
Less powder weight with Longshot for the same loads is a good thing though, both for economy and a little less recoil since the powder mass contributes more to recoil than the bullet mass.
Looking back at my load data, I'm using 13.4gr of AA9 for a very similar load to your 8.4gr of Longshot. My load might be a tad hotter but probably not by much, but it definitely puts out more blast and a little more recoil without a brake. I use a brake on that 6.5" barrel, so AA9 makes sense there; I think the Longshot load is better in my non-braked barrel.
Just for fun, here are expansion test (wet newsprint) results with the 200gr Mihec bullet and shallow hollow point with the above AA9 load. The two larger mushrooms in the middle are the 6.5" longslide, and the one less mushroomed on the left is the stock G20 barrel. Penetration from both was very impressive; the faster load just made a bigger hole.
![[Linked Image]](http://i24.photobucket.com/albums/c26/zthang43/Bang/molds/IMG_3934202.jpg)
