>>940066379
Gun under chin or gun in mouth, about a 30-40 degree angle. You're trying to blow our the brain stem instantly, not the just the brain. But the thing is, a 9mm is not the best caliber to do this with. You'd actually have better luck with a 22, or 12g slug under the chin. The 22 will bound around your skull and basically lights-out you before you can even register the pain, the slug will obliterate you instantly. 9mm can over penetrate, and while the expansion might make you a retard, if you do it wrong you won't die, you'll just be a retarded vegetable if the round passes straight through your head without obliterating the vital parts of your brain.
If you want to kill yourself, the best way is with the helium exit bag, not a gun. It's painless, you just go to sleep, you don't even realize you're dying.