Don't waste your time with such! I know I spent years doing so, everything you have ever read about ballistics is not true in the real world, except in the most general terms. This means (well it is kind of true), there is a very popular book on ballistics out there that had wrong math in it, it is the same wrong math used by gun writes for years. You can quote me on this, the difference in bullet drop when shooting up or down hill, has noting to do with distance! It has to do with the difference in gravity or the fact that the drop of the bullet becomes less, during the same time of flight. The only difference in distance is because the time of flight is longer the farther the bullet travels!!!!!!!!!!!!!!!!!!!!!!!!
1# Velocity testing by airgun makers is almost always done with the lightest pellets, which in turn leaves you with the most inaccurate pellets, in high powered guns! Velocities above or near the speed of sound are bad for pellet accuracy, those shot below this range usually shoot much better. Some pellets are made of very soft lead, and pushing them that hard usually deforms them and accuracy go south.
2# Airgun barrels often end up being choked, having a tight spot, sometimes this is intentional by the manufacture, like walther barrels, but in many cases it is cause by the crimping on of sights or breach blocks and such.
3# Pellets are stamped lead, well most are, and they are poorly made, case in point Crosman’s last batch of 177 caliber Premiers that I bought are so bad, that I thought that my very costly custom pcp’s were damaged! When you have a rifle that goes from shooting .2 or .3 at fifty yards, to one that won’t shoot inside an inch a forty you get real unhappy! Only a few hours of sorting and sizing in this extreme case solves most of the problem, but tossing half the lead does not make me happy. Nor am I thrilled with the improved groups, I guess I will have to switch to the JSB’s, even if I have to modify my guns to do so....
4# look for accuracy and not high velocity, because all the speed and power in the world won’t kill a mouse if you miss it!
5# pointed pellets usually have very bad ballistic coefficient, because they don't fly straight, that is to say that they almost never fly center on their axis
6# Round nose pellets have higher ballistic coefficients because even when they wobble, (yaw), they tend to stabilize as mush as they are going to in a very short time, unless they are deformed by the barrel or if they are unbalanced to begin with.
Jim Baumann
Author Air Rifle ballistics
