Rifle Projectile Ballistics
 
Ballistics, or the science of projectile motion, is frequently a hot topic in the shooting community. On many of our favorite shooting and hunting forms, a question or comment posted about ballistics will likely end in an argument. There are always plenty of opinions and anecdotal evidence, not always based on scientific fact. The first question one should ponder, before reading any further, do projectile ballistics matter to me? If you are shooting a modern high power rifle and your shots are less than 200 yards, then probably not. The fact is, most any bullet will do within this range, as long as the rifle is capable of the necessary accuracy AND the shooter can employ this accuracy. If, on the other hand, your hunting demands shots beyond this range and you and your equipment are up to the task, an understanding of projectile ballistics is imperative. This being said, and before any other discussion, there is no substitute for proofing your rifle at the range you intend to employ it. If you are going to hunt deer at 500 yards then you need to be able to shoot consistent groups at 500 yards and understand your ammunitions trajectory all the way to 500 yards.
  
In the shooting industry, a variety of standards are used to judge a bullets performance. A number that is frequently used to describe a bullets trajectory is ballistic coefficient. In short a ballistic coefficient is a number that is proportional to the deviation from Newtonian behavior of a bullet. There are many problems with using a ballistic coefficient (bc) to calculate bullet trajectories. First of all it is an empirical model. This means that it is a fit to observed data and not derived from first principles. Second, the drag model upon which our modern bc is based, is over a hundred years old. This would not necessarily be a problem except that bullet design and firearms have changed much since the late 1800's. With today’s aerodynamic high velocity projectiles, ballistic coefficients are seldom constant over a very wide velocity range. This is a source of much confusion and conjecture in the shooting industry. The fact is a better drag model is needed. A drag model based in fundamental physics or first principles that is easy to interpret is the holy grail of the shooting industry at this time. Unfortunately, it seems most companies (except the folks at DSB Scientific) are still trying to improve on the ballistic coefficient, sort of like booking a ticket on the Titanic.
  
You might therefore raise the question, why then do we provide the ballistic coefficient for most of our loads? The answer is simple; our customers want to see it. One can make the rough argument that comparing the bc's of various bullets under similar conditions will give a crude idea of relative performance. One can also argue that there are many programs on the market that can convert bc's to actual drop data. An excellent, and free, resource is JBM Small Arms Ballistics.