First question, to SAFELY shoot the 10 mm at full power you must have a fully supported chamber which does not come in the Glock 20 and most other factory guns.
What weapon do you have and do you have an upgraded aftermarket barrel?
I have some loads I have gathered around the web, I have NOT shot any of them yet and all of them require the upgraded fully supported chamber. USE AT YOUR OWN RISK! Here is a few:
200 grn Hornady XTP Hi Skor 800 X 9.4 grns for average of 1250 fps out of a 4.5" barrel
175 grn Winchester Silvertip Hodgdon Longshot 9.7 grns average 1365 fps 4.75" barrel
180 grn Hornady XTP Accurate #9 15.5 grns average 1400 fps
180 grn Hornady XTP Hi Skor 800 X 10.8 grns for average 1500 fps with a 6" long barrel
Again these are MAX loads, reduce and approach with caution.