1st of all, dont do it anon.>Will a .22 caliber rifle be enough for me to kill myself?
NOOOO. This is what paraplegic retards are made of. If you are going to do it jump of a tall bridge, just make sure its into a river and not into traffic, no need to fuck other peoples lives up. What i would personally do is hanging, but not the kick the chair type of hanging, the "on your knees" hang seems much better because it leaves room for regret, if you suddenly have a revelation while hanging you can stop the procedure but if you are determined to die you just keep going and fade to black. Remember to use vaseline on your neck to prevent hurting yourself with the rope.
If you are to scared to do it that way then it means you have something to lose and suicide is not the solution.
That being said, why not pretend suicide?
Go through the whole plan, get the rope, hang it, put the vaseline, write the suicide letter or whatever, put the rope around your neck, get in position and then abort. Clean up, leave the rope somewhere you can see as a reminder and go to sleep. Next day is your first day of your new life, you died yesterday, you've got nothing to lose now, all gain, get a new job that sustains you but allows you to pursue your passion or whatever, all the things you were afraid to do before, if it still frightens you, just remember, you were about to face the ultimate unknown, the black void, the scariest thing of all, get into a hobby, get friends, go out, met girls, whatever you felt you couldnt do before, you can do now.