I survived a self-inflicted gunshot to the jaw. I was a stupid kid and had no idea how to use a gun, let alone use one to CTB. This is the worst CTB method to survive but it's also probably one of the hardest to fail. If were talking about physical pain, it was the worst I've ever experienced. In the split second it took for the bullet to enter and exit, I could almost feel every fiber splitting. I imagine if I had hit my brain though, I wouldn't have experienced so much pain. I felt really hot, like meltingly hot. Imagine stretching a rubber glove enough to cause it to perforate. That's what my skin felt like. My ears were ringing, deafeningly loud. I felt my head hit the carpet under me and I couldn't do anything but writhe on the floor and feel my mom squeezing my head. At this point, the sensations were less painful and more uncomfortable. Like when your leg falls asleep or if you sleep on your arm and wake up with it numb.
Fear of pain and SI are the biggest things keeping people from CTB.
My biggest regret is not aiming where I should've. It still hurts, years later.
Best of luck to you.