As a preface to an upcoming series on subsonic rifles, I have compiled the following information regarding metals for bullets.
To produce good ballistics a bullet needs several characteristics.
- Internal: It has to remain solid at the temperature and pressures of firing, to avoid melting in the gun. It also must be softer than the barrel through which it is fired so that it conforms to the rifling of the barrel (which is critical to ballistic stability) and so that the barrel can be shot repeatedly without degrading.
- External: It should be as dense as possible, since density not only increases stability but also reduces the energy lost to air resistance during flight.
- Terminal: It needs to be tailored for some terminal objective. Depending on the target, we may want a bullet to explode, expand, penetrate, stop, or do some combination of those things.
Following is a list of elements that are of interest in meeting these objectives, ordered by density and noting their rough current cost: