... it is not completely true what I said that one should parametrize drag functions with power laws in order to get Pejsa's approach working - drag functions are parametrized with a series of constants  - cd(v)= c_i v_(i-1) < v =< v_i and power = 0

I will run a test. In princple I have a full runge kuta based trajectory simulator implemented - however I am not convinced that it would help sporting shooters, it would help non-friends is countries like Afghanistan.

the radar measurement... if the bullet went up a few kilometres, how do you know the conditions.... balloons?

This would be a relatively minor thing to do, compared with other adventures in mind. it is also easy with excel yourself. Just create a table where you supply a specific bc for a specific velocity range.

However, a bc is directly related to the drag function: deacceleration=drag/bc*(other factors). Hence the concept of multiple bc is the same as using multiple drag functions for different velocity ranges - which is in fact a new drag function. The current receipe for max accuracy is for most situations: use G7 and Litz BC. The Lapua data are not validated, much is unknown about them. With BfX it is also easy to fit your own BC

The quest for maximum accuracy, however, I pursue by providing 6dof, later. 6dof will introduce yaw depending drag, amongst others.

well, it proves the point that it is not trivial to compute.

I stick with my implementation of "Revised formula for the density of moist air (CIPM-2007), Metrologia 45 (2008) 149–155".

Back to QT. I have no clue how the radar measurements are done and interpreted. I have the following issue.

Under which elevations the bullets are fired?  How does one know the air density corrections?

(and  How does one know the properties for v0 close to 0?

If one fires a bullet at various v0, how does one correct for various yaw related effects on bc?)

No, it is not a problem, but an awful lot of work. BfX needs these functions as a set of power laws - the basis of Pejsa method. For power laws many physics equations can be integrated mathematically.

Yes, I see your point about the spin drift.

Ian,

this is getting impressive! I think you have to add a column that contains the sum of the spin drift to the wind deflection.

Robert

Ian,

there is a BfX user (mman) who wants to calculate shotgun properties. Did so before. On his request I put GS in. As it turns out the ballistics of spheres is more complicate to calculate than our sigar shaped ones. The issue here is that the drag properties these bullets, for sizes that are relevant for hunters, black powder and clay shooters do not scale in a simple way with physical dimensions. Something called the Reynold number plays a role - something I merely touched 30 years ago  in my physics career.  I am still studying the subject and may be BC=1 is a premature statement, hence I cannot really answer your question.

mman?

I have included a drag function "GS" for 9/16 inch spheres. To be used for shotfgun ballistics. Use it with BC=1 in every formula.

Later I will update BfX in order to provide a way for calculating the drag for other sized spheres.

Robert

it is a bit quiet on the forum. One of the reasons is that I am not very active with programming. To break the silence a bit I will mention here two things that I will implement shortly: a drag table for spheres to facilitate a forum member who wants to implement a ballistic calculator for shotguns, spin drift and the Miller stability criterium as soon as I have grasped how these formula's are derived, and the ballisctic coeficient calculator of Mac Coy.

Paul,

I just checked on a fresh vista32bit/excel 2007 installation the setup procedure.
I only downloaded bfxsetup.zip
I extracted the file into a certain folder (the desktop folder)
I ran bfxsetup
I opened excel 2007 and checked that bfx was not installed (e.g. =bfx_ ... does not give a response)
I went to the excel options menu
I opened add-ins
I pressed GO to manage excel addins
I browsed to the install directory and  added the bfx.xll
that was accepted and sow the bfxxll2007 addin in the addin list
I calculated something with bfx.

everything worked fine.

Then I googled on "xll The file you are trying to open is in a different format than specified by the file extension"

and found

http://www.mrexcel.com/forum/showthread.php?t=484698

Then I googled on "The file you are trying to open is in a different format than specified by the file extension"

http://www.itexperience.net/2008/03/17/excel-2007-error-different-format-than-specified-by-the-file-extension/

and similar links.

Both links seem to have remedies.

seems that you were uprgrading to Excel 2007 ....

... I have first to study the subject a bit ...

Ian, would it be beneficial to include the Miller formula in BfX?
Robert

Added conversion from Joule to foot-pound and vice versa e.g. =bfx_u("ft-lb";3000) converts 3000 J to foot pound

By the way,

At extreme angles - say the 32 degrees for max distance or 90 degrees for max heigth, the height dependent air density is an issue as a bullet easily goes up for two or three kilometres.