If using a firearm to the head, the most common danger is missing the important parts of the brain. Aiming under the chin with a shotgun can blow off parts of the face causing massive disfiguration, plus a hole through the windpipe, and still not be fatal. Shots to the front of the head may impair brain function (possibly causing paralysis) or affect personality, but still leave the parts of the brain that control bodily functions intact. Shooting through the temples can miss the brain by passing below it, but still sever nerves that go to the eyes, causing blindness. Stone1 goes into greater detail of the dangers of unsuccessful attempts. The prognosis for those failing using this method are rarely good.
For those aiming at other parts of the body, McKinley, Johns and Musgrove2 studied spinal cord injuries from gun shot wounds and other injuries caused by gunshots to the neck, chest, abdomen and back. Oparah and Mandal3 studied gunshot wounds of the chest.
Common outcomes include pain, infection, damage to the colon or intestines (possibly requiring removal and a colostomy bag), damage to diaphragm, liver, spleen, pneumothorax (results in a collapsed lung causing chest pain and breathing difficulties), haemothorax (blood accumulating in the pleural cavity) from internal bleeding of organs in the chest, spinal cord injuries (possibly resulting in para or quadriplegia) and other and non-spinal fractures.
However it is viewed, failing using this method is likely to cause very unpleasant injury.
Geo Stone, Suicide and Attempted Suicide, 1999.
W McKinley, J Johns, J Musgrove. Medical Complications and Functional Outcome of Individuals with Gunshot wound-Induced Spinal Cord Injury. Archives PM&R 1998.
SS Oparah & AK Mandal, Penetrating gunshot wounds of the chest in civilian practice: experience with 250 consecutive cases. Br J Surg 1978; 65: 45.