is there an easy way to compute ballistic coefficient?

Answer 1

Ballistic Coefficient 1
Here, you enter a known velocity for your bullet, and then either a second velocity or a time value followed by the distance travelled by the bullet for that second velocity or time value. Use the combo box to tell the program which value you wish to use. When you click on the calculate button, the other value (velocity or time) will be calculated and displayed. The resultant Ballistic Coefficient will be that coefficient for the drag function selected in the Shooting Parameters window. For example, if G1 is the currently selected drag function, enter 2600 ft./sec. for Velocity 1, 2500 ft./sec. for Velocity 2, leave time blank, Specify 'Use Velocity 2' for Select, and 20 yards for distance. Click on the calculate button and a G1 Ballistic Coefficient of 0.178 will be displayed. You will also see that the time to travel those 20 yards is 0.02353 seconds. The computation also incorporates the weather parameters currently defined in the Shooting Parameters window. The formula for this is as follows:

bc = [Cd(mach)](pi)(rho)(Vavg)(Vavg) / [(8)(a)]

where,

bc = ballistic coefficient
Cd = drag function
mach = mach number (bullet velocity / speed of sound)
rho = atmospheric density
Vavg = average bullet velocity, (V1 + V2) / 2
a = constant bullet acceleration over the interval


if you know V2 then:

time = distance / Vavg

if you know time then,

V2 = (2)(distance / time) - V1

and,

a = (v1-V2) / time

Note that the speed of sound as well as atmospheric density is a function of weather parameters.

Ballistic Coefficient 2
This calculation computes the ballistic coefficient when the bullet diameter, bullet weight, and form factor are known. Some early ballistics techniques allowed the determination of a form factor from charts where you could match the shape of your bullet to known shapes and extract a form factor for a particular drag function (see Hatcher's Notebook). The formula used here is:

bc= weight / [(form factor)(diameter)(diameter)]

Answer 2

Ooo... Good question. You can try the NAHC community forum (www.hunting.com -> member to member), or if you can't get in, i can ask the question and then email you back. Those guys in there are pretty smart. Let me know if you want me to ask it.

It's always nice to see another hunter!

Answer 3

check out field&stream.com they just wrote an article two months ago about it.