I'm partial to a hard cast flat nose bullet with a large meplat such as the grizzly cartridge 200gr WFNGC. However I have also killed several deer using 180gr and 200gr jhp's. Whatever you choose, make sure they are full power 10mm loads. A lot of the factory 10mm loads are not much hotter than the 40 S&W. Check out underwood ammo. They have several full power 10mm loads. And good luck with the Glock 20.