ballistic calculater

[cliffe]

what does the g1, g2 etc. gi,gl stand for in the ballistic caculator program?

 

[TheSilverFox]

Here's the short answer....lol in two steps

1---BALLISTIC COEFFICIENT,G1)

Simply put, ballistic coefficient, or BC, is a numerical definition of how well a bullet retains its velocity, as compared to a "standard" bullet.

A higher value indicates that the bullet will overcome air drag easily than a lower number will do.

The number is actually a ratio, compared to the bullet designated as the standard for that particular drag function.

Ballistic Coefficient =,Bullet Sectional Density) /,Bullet Form Factor)

In practice, the standard bullet is arbitrarily assigned a ballistic coefficient of "1.000." If we compare the velocity lost by the standard bullet,drag deceleration) against that of a sporting bullet that retains its velocity only half as well, we find that the bullet in question has a BC of approximately 0.500.

Take into account that BC values published by almost every commercial manufacturer, can not be used with any drag model other than G1.

It is possible to find other standard drag models by looking up historical military ballistics data.

But, if a standard drag model other than G1 is used, the BC values of bullets must be measured with reference to that drag model in order to calculate accurate trajectories.

The values are likely to be very different from the values referenced to G1

If the bullet retained its velocity only one quarter as well as the standard bullet, it will have a BC of 0.250.

Naturally, bullets having higher BC's will retain their velocity better and have flatter trajectories.

This results in greater energy at the target, and better resistance to wind deflection.

The BC's of most commercial bullets today are based on what is known as the SAAMI G1 drag model.

2---
Drag curves are referred to as the Ingalls, G1, G2, G5, G6, G7, and G8 drag curves.

Most bullet manufacturers assume and publish the G1 drag function shape. Examination of the form of a G1 standard-projectile, will to the obvious conclusion that it doesn't apply to the modern boattail bullet shapes in common use today. The G7 or G8 shape is much more appropriate but general availability of these ballistic coefficients is almost nonexistent.

Particularly, the G1, G5, and G7 curves model a specific bullet form, since they were deduced from, and it's common for some programs to adapt, modify ) the G1 drag curve in an effort to fit the G5 to G7 bullet shapes, and in other words, these approaches are, at best an improvement to model modern bullet shapes in order to make predictions more accurate.

That's why the BC must be defined as a function of velocity. The present solution uses the actual drag, and not rely on an average fit to a non-representative standard or table-based drag function.

In short, what these models can, is to compute accurate trajectory values if range is moderate, up to approximately 600 yards, beyond that, you need a different way to model air drag and to account specifically for a drag curve that matches your bullet dynamics.