Re: Free Recoil calculation spreadsheet
There's not sufficient input information to determine the average velocity vector of the molecules of the propellant gas. Certainly barrel length, expansion ratio, propellant pressure (or temperature) and the effect of a brake (if any) imake a difference in recoil even though all the parameters used in this spreadsheet are held constant.
Some programs (like Quickload) give one recoil emergy calculation as the bullet passes the crown and another value after the propellant has exited the barrel. The first number is the same wiith or without a brake. The second can be more or less with a brake and can be considerably different. Quickload however doesn't calculate the effect of a brake. Brake manufactures dont give performace data which can be used in calculations, at least none that I've seen.
This spreadsheet appears to be the result of empirically fitting of measured data from tests on typical rifles without brakes. For that I expect it works fairly well.