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#31
##### Ballistics / Re: Weapon Employment Zone
June 15, 2014, 11:36:12 AM
Ok,
I understand what you understand - nothing special meant here. Let me make things less abstract.

Basically what Monte Carlo does is to generate "outcomes", e.g. where a  bullet ends, for, varying conditions - the input parameters. The input parameters are varied according to a certain probability distribution. If for example a shooter is able to aim with an accuracy of 1 MoA then people like me model that as a bell-shaped (Gaussian) probability distribution that averages to 1 MoA mean inaccuracy. With this we acknowledge the fact that in some cases the shooter aims very well and in others badly.

In a Monte Carlo simulation then, the computer draws a random number and converts that to an inital horizontal and vertical aiming angle. This is done in such a way that average inaccuracy is 1 MoA. After the horizontal and vertical launch angles are chosen, the bullets trajectory is calculated.

If, for instance, in addition the effects of a non-constant wind is being studied, one might model that primitively as a wind distribution that is half of the time zero and the other half 1 m/s. In a Monte Carlo calculation then one first draws a random number that determines the launch angle, and an another random number is used to determine if there is wind or not in the trajectory calculation (with the afforementioned spreadsheet I deal on a more sophisticated way with non constant wind along a trajectory). Hence we end up with a set of bullet end coordinates that  were affected by both wind and the shooters abilities.

In practise, the more inputs one generates according to a probability distribution, the less the details of a probability distribution matters. The distribution might as well be flat, meaning that the probability for a certain input value is constant in a certain range and zero elsewhere.
#32
##### Ballistics / Re: Weapon Employment Zone
June 12, 2014, 01:38:37 PM
Maybe "Monte Carlo" is a  definition issue. In this case, i imagined that input parameters are generated in such a way that they are consistent with a certain probability distribution. Then a trajectory calculated and evaluated. The process is repeated hundreds of times. This is what one might describe as Monte Carlo.

#33
##### Ballistics / Re: Weapon Employment Zone
June 11, 2014, 01:16:00 AM
WEZ is a Monte Carlo simulation.

I find it hard to opinate about it - it does what it says.

Quite frequently I use a similar tool understand ballistic effects in a target shoot competition setting.

It is available as download on the BfX site. Look for the descriptive text:

"This workbook hosts a simulator with which you can estimate your results in a (multi distance, multi target) match, e.g. the NRA 90 shot full bore regional match course."
#34
##### Member projects / Re: CFD modelling
May 24, 2014, 08:35:59 PM
#35
##### Member projects / Re: CFD modelling
May 24, 2014, 08:28:27 PM
cool!

what I need are parametrizations of 6dof coefficients for boat tail bullets. No other projectiles.
#36
##### Ballistics / Re: Vertical Deflection due to a Crosswind aka Aerodynamic Jump
April 30, 2014, 08:29:53 PM
The problem with these matters is that assumptions are made "e.g bullet flies in the direction of the wind" and presented as facts.

Even they are somewhere along the trajectory true, there is a period they are not valid. What happens then.

Nevertheless, I have time to spare I will read better the article.

Robert
#37
##### Member projects / Re: Ballistic_XLR a modification of the Jackson Rifles Workbook by Meccastreisand
March 16, 2014, 11:37:44 PM
Indeed, BfX does not work on a Mac.

In short I will have a look at your work!
#38
##### Ballistics / Re: Spin Drift
March 03, 2014, 08:16:21 PM
mman has a 1000m+ range in his backyard! Shall we  ask him?

The problem, of course, is to do the measurements.

In those measurements one has to vary some quantities that affect spin drift and other factors that affect horizontal displacement. Then there is wind and measurement errors. To single out to spin-drift effects one must trust the proper computation of all other effects that deflects the bullet. I would guess that only a professional organisation is able to do the measurements.

As far as I know, the US Army is the only institution that published measurements.

Brian did the best next thing. He used a proffesional 6DOF ballistic program - PRODAS - and fitted the spin drift of bullets.
#39
##### Ballistics / Re: Vertical Wind
February 24, 2014, 04:14:16 PM
In the Netherlands there is nothing a shooter can shoot at that requires an elevation of more than a degree...
#40
##### Member projects / Re: 6Dof bullet parameters
February 07, 2014, 12:24:30 AM
no, i cannot lay hands on a proper set of formula's for the bullet 6dof parameters.
#41
##### Member projects / Re: Ballistic_XLR a modification of the Jackson Rifles Workbook by Meccastreisand
January 15, 2014, 01:59:39 PM
svorog1, we need more details.

can you post the spreadsheet so that we understand what you are doing?
#42
##### Member projects / Re: Ballistic_XLR a modification of the Jackson Rifles Workbook by Meccastreisand
January 05, 2014, 08:31:40 PM
Sometimes I wonder what to add to BfX given that there are spreadsheets, like this one, that does so much! Clearly, being able to run on a Pocket PC brings ballistics in the field.

#43
##### Member projects / Re: 6Dof bullet parameters
December 16, 2013, 06:40:24 PM
but the missing values are small?
#44
##### Member projects / Re: 6Dof bullet parameters
December 15, 2013, 11:04:15 PM
Cool! a pitty that I cannot embark on the matter myself, I have other science to do.

I know that you can shoot the distances to test your own calculations. Can you measure the distance that your bullets start to toggle (shoot keyholes) because their velocity goes below that of sound (and the nose pressure gets a factor of 3 to 5 higher?).

I would reload as low as safe, to have low muzzle velocities and put paper targets every 10 meters in the neighbour hood where the bullets goes below the velocity of sound.

Probably statistics is involved, hence you should have statistics of the number of keyholes per meter....

?
#45
##### Member projects / Re: 6Dof bullet parameters
December 14, 2013, 11:46:46 PM
thx, have a look at the code in ad0915628 - i mentionned in a previous post that i salvaged much of it. however 6dof equations of motions are not so difficult to implement. the hard thing is to get the aerodynamic coefs right,