Contrary to the weird policy-justifying fantasies of the left suicide by gun is not painless or instant. I recall a story of a lawyer who committed suicide with a .38 revolver. He fired five shots into the side and front of his head as his secretary struggled to unlock the door to his office. He lived for some time after that in horrendous agony. A kid that I knew from another church when I was a boy put a shotgun in his mouth and pulled the trigger. He got the angle wrong and only managed to blow his face off. The last I heard he is still alive in an institution.
Real life isn't like the movies. It is messy and imprecise.
The trick is to hit the brain stem. Which can be problematic, as it’s hard to shoot yourself from behind, and going in from the front isn’t easy to line up, even if you are in your right mind and know what you’re doing. Fortunately, people in their right minds with the patience to plan and follow through aren’t apt to kill themselves.
Maybe better to pay a Marine sniper to do it. Or post seditious “right wing extremist” chatter on the internet and wait for Obama to dispatch a drone.