1. Using a shotgun rather than a gun or rifle. In his study of gunshot injuries in Mobile Alabama
1, Riddick found that of those surviving a firearm suicide attempt, 80% used a handgun, 15% a rifle, and only 5% a shotgun. However, shotguns can be more difficult to aim into the side and back of the head, which are the most fatal points to aim (see below). They do deliver much greater energy at impact though (meaning they can do more damage).
Bullets that mushroom on impact cause more damage than those that don't. For this reason, bullets with full metal jackets (tip of the bullet is metal as well as the case - see
http://en.wikipedia.org/wiki/Full_metal_jacket_bullet) should be avoided as they do not expand.
One knowledgeable reader of this website wrote in to suggest that those using a shotgun should consider using shotgun shells that shoot slugs, which is one piece of lead instead of a number of smaller balls of lead. Or else if using shot, to use buckshot, which can come in 0.24 - 0.36 caliber, instead of 0.05 which is used for things like clay pigeon/skeet shooting. The higher the caliber, the bigger the pellets (meaning they better maintain their speed and energy on impact)