Re: sectional density\'s effect on bullet performance
sscoyote, SD or sectional density is a measure of mass to cross section of a projectile. For a given caliber, higher SD means greater penetration IF ALL OTHER THINGS ARE EQUAL.
SD is used to calculate ballistic coefficient(BC). BC is a measure of how well a projectile retains velocity in comparison to a standard projectile. Any number less than 1 means it retains less velocity at a given range, 1 is equal, and more than 1 denotes more retained velocity. Another way of looking at it is that it reflects a bullet's drag characteristics.
In calculating BC, the bullet's FORM is considered in relation to SD, which presents a NON-DIMENSIONAL value for comparison. BC for a given form is directly proportional to SD.
Try "Understanding Firearm Ballistics" by Robert Rinker. It is a cheap and time saving education, which cover interior/exterior and terminal ballistics. Luck.