http://www.accuratepowder.com/data/...a/40Cal(10mm)/10mm Auto Pages 121 and 123.pdf
http://www.ramshot.com/powders/
For high performance loading of 10mm, AA#9 is as good as it gets unless you want to spend the extra money for Vihta Vouri 3N38 or N105, but then, data will not be nearly as available as what exists for #7 & #9. Good and realistic data is available for Ramshot Silhouette at their website. Max. performance will take you close to what #7 will provide, and the truth is that 90% of 10mm shooters are NOT going to need it. For Delta Elites, or DW 10mm pistols, any of these three will get you what is realistic.
#7 has been proven to be one of the best available powders for 10mm, and it has been as long as data has been around for the cartidge. #9 will get you performance equal to the original Norma loads. If you want to see some of the negative effects of using the hot 800-X loads, go to this link:
http://www.czshooters.com/forum/viewtopic.php?t=1614 Take a look at the primer in the pic. This is an example of what you don't want to see! These same loads were also circulated at CZ Forum and probably originated with guys hotrodding Glock 10mm pistols on the various Glock forums, but in the case of use in Witness pistols and these two websites, the data was provided by the guy who makes Double-Tap ammo.
If someone has a need for higher performance in 10mm that what #9 will deliver, you probably want to watch the guy (from a safe distance) who's providing the data while he shoots these loads rather than waste your time and possibly endangering yourself, or your pistol. With a Glock 20, that does have a stronger locking system than Witness pistols, but weighs what, 25 ounces? I can guarantee you the level of accuracy they get will be mediocre at best. The question of adequate chamber support also exists with Glock 10mms.
If you have to trickle powder for a handgun load, that should be enough right there to tell you it's the wrong choice, most especially for max. loads. Many are throwing these charges with a powder measure and NOT trickling. AA#7 is the densest handgun propellant available to handloaders at 985 grams per liter .985/cc. Coupled with its small physical size, metering is about as good as you can expect from any handgun powder. #9 is nearly as dense (935 grams per liter) and a bit finer grained. The only good reason for not using one or the other may be a powder measure that doesn't seal well enough to prevent leakage. Then, there are far better choices than 800-X. Talk to anyone that shoots .45 ACP regularly. Look at the data and performance level of the majority of loads cirulating around the forums. It is clear that a lot of them are not interested in +P level loads. Recoil can be substantial. Power factors will be at 210 or above when the comfort level for most shooters runs 160-165, yeah that's why you see IDPA and USPSA shooters using the 165 power factor minimum. A person that can handle recoil with loads above 200 Power factor in an autoloading pistol, and shoot them accurately, has put in a lot of time in learning to master recoil. The 180 grain 10mm loads with the charges of 800-X that you won't find in any published manual, yet circulate, take you to yet another realm of recoil in pistols the same size as .45 pistols that many shooters can not master with .45 ACP +P loads. That's just my oppinion!