[Unclenick]

Casting is melting lead or a lead alloy and pouring it into a mold to form a bullet.

Swaging is using a pressure ram to force a slug of lead wire into a forming die hard enough to force it to assume the shape of the die.

Swaging alloy has to be malleable enough to be formed in a die at practical pressures. There is a limit to how hard it can be, therefore. Cast bullets are not quite as dimensionally uniform as swaged bullets, but the mold lets you pour alloys without regard for their solidified hardness. Typically, cast bullet are therefore harder. Also, you can mold recessed rings into them for accepting larger quantities of lubricant than you can get the surface of a swaged bullet to accept. Taken together, these two things mean they can usually be driven to higher velocities. Swaging is more suited to high speed mass production than molding, so most lead bullets from large volume bullet makers are swaged, while cast bullets are more common among smaller volume and independent lead bullet makers.