## Bfx ballistic calculator with 6-dof corrections

Started by mman, May 16, 2012, 06:25:41 PM

#### mman

I have used this calculator for a while now.. Feel free to download it and please let me know if you find any bugs. Includes following 6-dof corrections to vertical and horizontal deflections:

Spin drift (Litz)
Vertical and horizontal Coriolis (Litz)
Up/downhill shooting (Litz's improved riflemans rule)
Range wind drift (McCoy)
Aerodynamic jump aka crosswind vertical drift (Litz)
Wind weighting factors (McCoy)
Muzzle velocity temperature coefficient (linear inter/extrapolation)
Effect of atmospheric conditions to vertical zero range
Possibility to use horizontal zero to compensate spin drift for short ranges

I would say this is as accurate as it gets. Recommended for extra long ranges. I think there is no more external ballistic phenomena to correct. Or maybe effect of vertical wind component could be included? Calculator is pretty easy to use at the range when there is own sheet for every gun/load. Before shooting just "TARGET INFORMATION" and "ATMOSPHERIC CONDITIONS" values have to be changed. Everything else have to be set only for once. There is two default sheets: one for BC input and another for lapua bullets (radar drag data available).

http://www.2shared.com/file/YEE1WaWl/Ballistic_calculator.html

Would it make sense to add your and Ians algorithms to BfX - awaiting the time that I have time and energy to a 6dof bfx?

#### mman

#3
I don't know exactly what you mean, but fine by me in any case. Equations in my sheet can be found from literature so they are free to use anyway. I think at least spin drift, aerodynamic jump and coriolis would be useful for some users...

By the way would it be lot of work to include inverse functions to Bfx? For example if BfX_D equals drop for the range of 100 m, inv(BfX_D) would equal range for 10 cm drop? I think some of us would find applications for this.

EDIT: I came across this today:
http://bulletin.accurateshooter.com/2012/05/new-ballistics-app-from-bryan-litz-for-android-devices/

Reticle aiming point calculation is a nice idea. I made my own for standard mildot reticle:
http://www.2shared.com/file/rZp3RuGk/Ballistic_calculator_with_mild.html

Quote from: mman on May 18, 2012, 02:12:17 PM
By the way would it be lot of work to include inverse functions to Bfx? For example if BfX_D equals drop for the range of 100 m, inv(BfX_D) would equal range for 10 cm drop? I think some of us would find applications for this.

It is certainly possible, some times a bit tricky. Is bfx_i already not good enought to find the inverse:

#### mman

Thanks for the tip, I think bfx_i makes the trick.

#### gvp

#6
Quote from: mman on May 16, 2012, 06:25:41 PM
Includes following 6-dof corrections to vertical and horizontal deflections:

Spin drift (Litz)
Vertical and horizontal Coriolis (Litz)
Up/downhill shooting (Litz's improved riflemans rule)
Range wind drift (McCoy)
Aerodynamic jump aka crosswind vertical drift (Litz)
Wind weighting factors (McCoy)
Muzzle velocity temperature coefficient (linear inter/extrapolation)
Effect of atmospheric conditions to vertical zero range
Possibility to use horizontal zero to compensate spin drift for short ranges

fantastic job mman, thank you !!!

can you please explain me the "Effect of atmospheric conditions to vertical zero range" ... I think it's the "Constant zero" cell.
when I must set yes or no ?

#### mman

Quote from: gvp on May 27, 2013, 04:28:09 PM

fantastic job mman, thank you !!!

can you please explain me the "Effect of atmospheric conditions to vertical zero range" ... I think it's the "Constant zero" cell.
when I must set yes or no ?
Thanks! As it reads on comment: "If constant zero is chosen (value y) it is assumed that atmospheric conditions has no effect on vertical zero range." (with typos corrected )

Well, I guess this doesn't help you with choosing... You should choose "Yes" if you have seen at range that your zero does not change even when atmospheric conditions do. If we look at external ballistics your zero depends on temp, pressure, hum and muzzle vel but in practice this is not always the case. This is because internal ballistics can compensate the effect of external ballistics. It is actually very complicated topic and for gaining deeper understanding I recommend you to read this page:

http://www.varmintal.com/aflut.htm

In short vertical barrel vibration can change your zero on different conditions as well. But if you have no practical range results, probably better option is to choose "no" and then internal ballistics is excluded and your zero is not constant but depends on atmospheric conditions. Anyway if you zero your gun on short range this is not very critical but with long range zero it is. This is one of the reasons not to zero your gun much longer than 150 meters. Personally I use 130 meter zeros for centerfires and 50 m zeros for rimfires.

thank you ...

#### gvp

a little correction to your 6dof workbook

in cell p11 you entered
=0,00007292*E16*T10*SIN(E19)*1000/H4

the correct is
=0,00007292*E16*T10*SIN(E19*pi()/180)*1000/H4

#### mman

#10
Quote from: gvp on May 30, 2013, 11:54:27 PM
a little correction to your 6dof workbook

in cell p11 you entered
=0,00007292*E16*T10*SIN(E19)*1000/H4

the correct is
=0,00007292*E16*T10*SIN(E19*pi()/180)*1000/H4

Yeah you are right. Thanks! It happens to be that on my latitude the difference is very small so I haven't noticed the error.

#### gvp

mman, just a confirmation if the following terms-effects are the same ...

Crosswind drift = Aerodynamic jump = Magnus effect ?
Coriolis @vertical axis = Eotvos effect = vertical component of Coriolis force ?
Coriolis @horizontal axis = horizontal component of Coriolis force ?
Spin drift = Gyroscopic drift ?

thanks ...

#### mman

Crosswind drift = Aerodynamic jump = Magnus effect ? No

Crosswind vertical drift = Aerodynamic jump on my 6-DOF calculator but aerodynamic jump is actually more general phenomena which causes drift when projectile's orientation changes against oncoming airflow. Aerodynamic jump is a result of lift force which is actual aerodynamic force. Also spin drift is a cause of lift force. Magnus effect is a result of actual magnus force but this is usually neglected at bullet trajectories because it is so small.

Coriolis @vertical axis = Eotvos effect = vertical component of Coriolis force ? CONFIRMED
Coriolis @horizontal axis = horizontal component of Coriolis force ? CONFIRMED
Spin drift = Gyroscopic drift ? CONFIRMED

#### 375CT

Mman, more a request than anything else!

I've been playing with the SS and it's a great work, but I wonder if you can update it to make ready to Firing Tables

I mean, some kind of grid, with Range, Path and Wind Drift, say from 0 to 2000

Anything like that will be very useful.