if i shoot at angle say 30 degrees and my range finder gave me 600y thats 424y horizontal i will use 424 for elevation settings but use 600 for wind setting am i rignt?my next question is where barometric pressure is suppose to be use for elevation et windage? thanks
am i right....ballistic
- Thread starter boblee
- Start date
No, as the crow flies for wind. No again on the 424, gravity absolutely not as the crow flies, you need a computer.
Two kinds of pressure:
There is "station" pressure - the actual air pressure in the measurement location, unadjusted for altitude. If you have a Kestrel Pocket Weather Meter, you would leave the altitude at zero.
"Barometric" pressure is air pressure adjusted for altitude by a fairly simple formula. This is what weather reports usually use. With the Kestrel Pocket Weather Meter, you would enter the actual altitude.
So if you have a number for pressure, is it Station, or adjusted to sea level? And what does your ballistics program use? If the program has an "Altitude" box, it is Barometric, adjusted to sea level.
If the program has no altitude box, it is Station pressure.
Two kinds of pressure:
There is "station" pressure - the actual air pressure in the measurement location, unadjusted for altitude. If you have a Kestrel Pocket Weather Meter, you would leave the altitude at zero.
"Barometric" pressure is air pressure adjusted for altitude by a fairly simple formula. This is what weather reports usually use. With the Kestrel Pocket Weather Meter, you would enter the actual altitude.
So if you have a number for pressure, is it Station, or adjusted to sea level? And what does your ballistics program use? If the program has an "Altitude" box, it is Barometric, adjusted to sea level.
If the program has no altitude box, it is Station pressure.
rnbra-shooter
CGN Ultra frequent flyer
- Location
- New Brunswick
Hmmm if the distance from you to the target is 600y, and you are shooting uphill 30 degrees or downhill 30 degrees, the horizontal distance to the target would be Cos(30deg)*600y = 519yards.
You would use your "519 yard elevation setting" in order to make this shot.
Hmmm I never thought about wind settings but I think you are correct (use 600y wind deflections).
Barometric pressure (and also temperature and humidity) affect the air density. Drag on the bullet (and therefore, the amount that the bullet slows down, and also the amount that the bullet gets pushed sideways by the wind) is directly proportional to air density.
You would use your "519 yard elevation setting" in order to make this shot.
Hmmm I never thought about wind settings but I think you are correct (use 600y wind deflections).
Barometric pressure (and also temperature and humidity) affect the air density. Drag on the bullet (and therefore, the amount that the bullet slows down, and also the amount that the bullet gets pushed sideways by the wind) is directly proportional to air density.
But this would not be accurate. Try it with a ballistics program, it isn't the same.
Because:
Gravity is no longer operating at 90° to the bullet, so gravity does less (a fishing rod at 45° sags less than a horizontal one, OK?).
Your sights are higher than the bore, which changes the zeroing geometry.
The bullet takes longer to get there, and slows down (this is the easiest reason to understand).
If you don't input altitude into the Kestrel, a direct reading, input 0 into the program for altitude. So the program won't re-adjust for altitude.
arcticcathonda
CGN frequent flyer
- Location
- Southern Alberta
need to think this through before I open my yap!
0 Degrees drop - GunSim (requires Java): http://www.gunsim.com/save.html?name=Lapua%20Hunting%20308%20Win%20Mega&rang=300.0&bc=0.319&velo=2510.0&grou=2.0&zero=300.0&wind=10.0&tars=0.0&temp=59.0&pres=29.92&drag=0&bulw=155.0&alti=0.0&humi=0.0&sigh=1.5&uphi=0.0&tarw=10.0&tarh=10.0&yard=true&tab=2
Drop at 700 yards, 0 degrees = -228.25"
The Rifleman's "Cosine Rule" method says that 1000 yards at 45 degrees is the same as 700 yards horizontal:
http://4.bp.########.com/_bP_PNTfFn9I/ShR9jIYJmLI/AAAAAAAAAFc/sFpze3qoTG4/s400/riflemansmethod.gif
So instead of -228.25", we take the drop at 1000 yards, -672.94.
Let's try using a computer:
45 degrees drop - GunSim (requires Java):
Drop at 1000 yards, 45 degrees: http://www.gunsim.com/save.html?nam...uphi=45.0&tarw=10.0&tarh=10.0&yard=true&tab=2
Actual drop at 1000 yards, 45 degrees = -413.58
A 21 foot difference. Color me picky, but that isn't close enough for me.
You would be closer making no adjustment at all than using the rifleman's method in this case.
A. J. Pejsa "Modern Practical Ballistics" Ch 12: (The Rifleman's method) "To correct for the effect of an incline, they recommend imagining that the distance to the target is reduced to its 'horizontal component' ... This is the worst possible advice, and can cause serious errors in long-range shooting on steep inclines".
Too right.
Drop at 700 yards, 0 degrees = -228.25"
The Rifleman's "Cosine Rule" method says that 1000 yards at 45 degrees is the same as 700 yards horizontal:
http://4.bp.########.com/_bP_PNTfFn9I/ShR9jIYJmLI/AAAAAAAAAFc/sFpze3qoTG4/s400/riflemansmethod.gif
So instead of -228.25", we take the drop at 1000 yards, -672.94.
Let's try using a computer:
45 degrees drop - GunSim (requires Java):
Drop at 1000 yards, 45 degrees: http://www.gunsim.com/save.html?nam...uphi=45.0&tarw=10.0&tarh=10.0&yard=true&tab=2
Actual drop at 1000 yards, 45 degrees = -413.58
A 21 foot difference. Color me picky, but that isn't close enough for me.
You would be closer making no adjustment at all than using the rifleman's method in this case.
A. J. Pejsa "Modern Practical Ballistics" Ch 12: (The Rifleman's method) "To correct for the effect of an incline, they recommend imagining that the distance to the target is reduced to its 'horizontal component' ... This is the worst possible advice, and can cause serious errors in long-range shooting on steep inclines".
Too right.
The line of sight(lasered range) is not the true target range on up down shots. The horizontal range is the range for both elev. and windage.
Barometric pressue is the pressure reported by meterologist.
Density altitude is what matters. The altitude at the shot in relation to the temp. at the shot, not what the barometer is 1/2mile away.
Barometric pressue is the pressure reported by meterologist.
Density altitude is what matters. The altitude at the shot in relation to the temp. at the shot, not what the barometer is 1/2mile away.
Jordan Smith
CGN Ultra frequent flyer
- Location
- Calgary, AB
WRT windage- you have to remember that the wind affects the bullet NOT over the horizontal range, but all along the line of sight path to the target. Use the line of sight range for wind correction.
