Up/Downhill corrections

[Brown Dog]

aaagh! [img]/ubbthreads/images/graemlins/grin.gif[/img]

[BLASERMAN]

So correct me if I am Wrong 0 - 600 use the cosine
and it should work.

[Mikecr]

Sierra's improved rifleman's rule:
PATH + DROP*(1-COS(ANGLE*PI()/180))

As stated, TOF is same, DROP is same, but PATH is adjusted for angle shooting.

[Gustavo]

To make sure that I understand the initial example, and that if range is not stretched far beyond 700/800 yards the use of Field Charts is very appropiate as long as atmospheric standard conditions are used, if we only know altitude.

Here goes an example, where the shooter can interpolate the middle values for the incline angle, just to obtain a sensible, good prediction for a first shot.

Of course, Field Charts are handy, since they never run out of batteries, are imprevious to rain and sun, and they cost nothing!

First the values I used :



Second the complete results



and finally a Field Chart, that in this case calls for a rapid interpolation in order to find an approximate value for an incline of 25°

[Mikecr]

Gustavo
Standard pressure for 5000' altitude is 24.9"Hg, 41deg, and 0% humidity.
Why do you think standard conditions at altitude will fairly represent actual shooting conditions? Is it 41 degrees there?

[Gustavo]

[ QUOTE ]
Gustavo
Standard pressure for 5000' altitude is 24.9"Hg, 41deg, and 0% humidity.
Why do you think standard conditions at altitude will fairly represent actual shooting conditions? Is it 41 degrees there?

[/ QUOTE ]

Mike you are right, those are not the standard conditions, I just used the same data as posted by Eaglet in order to compare notes regarding the previous data.

My post regarding the use of atmospheric standard condtions was not related to the example at all. Was just a friendly reminder.

Hope this clears the issue for good [img]/ubbthreads/images/graemlins/smile.gif[/img]

BTW, you are a good observer and made a nice point!

Here goes a graphical output ( Path in MOA ) of the same dataset, from level fire ( Track-1) to an incline of 50° in 10° steps. Just to complement the original point made by Shawn.

[goodgrouper]

Ok, thanks for that Eaglet. I understand what he was saying now. I have always multiplied the MOA or actually the IPHY by the cosine to get the correction but have also told people that don't want to do that because of "heat of the moment" jitters that they can times the range by the cosine and still make a kill. In your example, doing this would cause a 4" low hit at 800 yards on a 28 degree angle which would still kill a big game animal. And 28 degrees is ONE HECK OF AN ANGLE! That big bull we killed last year at 1302 yards was at the top of a mountain and we were at the bottom shooting straight up at it and if memory serves, it was only a 20 degree shot. You would be hard pressed to find an angle steeper than this.

Most shots even out here in the west are going to be 10 degrees or less most of the time and that would only cause a miss of a couple inches or less at 800 yards dialing of the cosinexyardage. The deer ain't going to know the difference but it is still a good observation and one to be aware of. Good thread.