You're going to obviously be firing from close range. The shell should easily penetrate the skull. You could always fire into your mouth. If aim straight should sever the spinal cord without penetrating the skull, but that's instant death. Shotgun to any part of the head is statistically the best chance of successful ctb over all other methods with probability of success over 95 percent. Higher than all other firearms or attempts to other parts of the body. Having said that, I actually knew a guy who survived that type of blast initially. Eventually died after a couple years of hospital stays and surgeries. A lot of painful stuff!