In the middle of the last century, bullet bras became fashionable among Western women, mainly Americans. With the bones perpendicular to the body, they really resembled the cone-shaped part of a bullet. The popularity of this kind of lingerie was brought by the so—called sweater girls - Hollywood actresses who got into the habit of wearing "bullets" under wool sweaters. By the 60s, fashion swerved in the other direction, and everyone forgot about the "bullets".
Perhaps enough theory. We're here for the photos, aren't we?