Re: What Ballistic Progam?
The Pejsa equations are flexible and simple to program. At high supersonic speeds (above 1300-1400 fps), the program can be very accurate.
As with all things, there's no free lunch.
The price you pay for simple equations is that the bullet description becomes more complex. Traditional solutions only require a BC referenced to some standard (G1, G7, etc) However the Pejsa solution requires more information about the bullet including retardation coeff, something you have to shoot at multiple distances (under carefully measured conditions) in order to establish for each bullet.
A further limitation of the Pejsa method is that it requires 'creative' manipulation at transonic speeds. The analytic equation that's used to describe the bullets drag coefficient is very precise in the high supersonic region (above 1300-1400 fps), but begins to diverge, depending on projectile shape, as it slows down. The shape of the drag curve at transonic speed is essentially 'made up' by the programmer, and no two Pejsa solutions are likely to return the same answers below 1300 fps. For this reason you can expect increasing error (more drop) at longer ranges and slower flight speeds. I believe this is what ch'e is seeing above (Pejsa program predicted the most drop).
One last thing about the Pejsa method: it doesn't account for effects of air temperature on speed of sound. The speed of sound changes with air temperature, and the drag coefficient is a function of Mach number, which depends on the speed of sound. In Pejsa's solution, the bullet's drag coefficient is purely a function of velocity, which will introduce errors in non-standard temperature, especially at flight speeds near the speed of sound. Note: this temperature problem isn't unique to Pejsa, the well known and commonly used Siacci method suffers from the same limitation.
Regarding the <span style="font-style: italic">accuracy</span> of ballistics programs, nothing beats JBM. It doesn't have all the graphic displays and libraries of the high dollar programs, but it runs a proper numeric solution, and returns answers that are truly as accurate as the inputs. I always recommend JBM, using BC's referenced to a proper standard (G7 for long range bullets) as the standard to compare the accuracy of any ballistics program.
-Bryan