echo3mike
Member
Shooting Exercise I-A: Mirage
-There are a number of ways to determine wind speed and direction. At longer ranges, one of the most predictable is mirage. It's often difficult to see the leaves rustling from a 3-5mph wind when you're 800yds away. However, by focusing the spotting scope to rougly 1/2 to 2/3 of the distance to the target, the wind speed and direction can be obtained...with practice and experience.
Alot of reading mirage could be called SWAGging, but there are some basic guidelines to this "art". A "No Wind" value means just that...there's no wind blowing at the point of focus, and the mirage is generally going straight up. This can often be confused with a "boil", which is usually seen when you're looking directly into or away from the direction the wind is blowing, i.e. headwinds or tailwinds. A rough idea of wind direction is usually indicated by which way the mirage is "moving"...left to right / right to left. Wind speed can be guesstimated by how fast the mirage "looks"...if it's a stronger wind, the mirage will move faster, and the moving mirage might look closer together.
Exercise I-A
-Using the data obtained in Shooting Exercise I (your data / my data...it doesn't matter) and ANY OTHER SOURCES,
A) Where would you point your spotting scope to obtain the wind direction?
B) What would the mirage look like when the spotting scope is pointed toward the target (speed and direction)?
C) You're shooting into a "rapid boil". Would there be any changes to your POI (theoretically)?
Shooting Exercise I-B: Meteorlogical and Environmental Effects
Most of us don't shoot in vastly different locations with any frequency. The effects of weather and the environment don't play a signifcant role in our ranging or sight adjustments. But the effects of environmental and meteorlogical (ENV/MET) variables can have a drastic effect on POI when the location changes dramatically. Most of the ballistic tables are prepared around Standard Atmospheric Conditions (SAC): 59.5 degrees F, Barometric Pressure of 29.92in Hg, 0% Humidity, and 0ft ASL. At short range (100 - 600yds), the effects of different ENV/MET variables aren't that important and can be neglected. And, depending on the caliber, even at ranges out to 1000yds the change isn't that great. But it can add up and change your POI considerably.
As with mirage, there aren't any hard, fast rules but there are guidelines: Temp up / sights down...Humidity up / sights down...Baro P up / sights up.
Exercise I-B
-Using the data from Shooting Exercise I (mine/yours..irrelevant: Sierra .308cal 150gr FMJBT, BC of 0.226, MV of 2740fps) and ANY OTHER SOURCES, what are
A) The elevation for 800, 900, 1000 yards at SAC
B) ..at 95 degrees
C) ...at 85% humidity
D)...at 30.35 in Hg
E) all of the above combined
F) Why, when you correct for Barometric Pressure, you simultaneously correct for altitude?
S.
-There are a number of ways to determine wind speed and direction. At longer ranges, one of the most predictable is mirage. It's often difficult to see the leaves rustling from a 3-5mph wind when you're 800yds away. However, by focusing the spotting scope to rougly 1/2 to 2/3 of the distance to the target, the wind speed and direction can be obtained...with practice and experience.
Alot of reading mirage could be called SWAGging, but there are some basic guidelines to this "art". A "No Wind" value means just that...there's no wind blowing at the point of focus, and the mirage is generally going straight up. This can often be confused with a "boil", which is usually seen when you're looking directly into or away from the direction the wind is blowing, i.e. headwinds or tailwinds. A rough idea of wind direction is usually indicated by which way the mirage is "moving"...left to right / right to left. Wind speed can be guesstimated by how fast the mirage "looks"...if it's a stronger wind, the mirage will move faster, and the moving mirage might look closer together.
Exercise I-A
-Using the data obtained in Shooting Exercise I (your data / my data...it doesn't matter) and ANY OTHER SOURCES,
A) Where would you point your spotting scope to obtain the wind direction?
B) What would the mirage look like when the spotting scope is pointed toward the target (speed and direction)?
C) You're shooting into a "rapid boil". Would there be any changes to your POI (theoretically)?
Shooting Exercise I-B: Meteorlogical and Environmental Effects
Most of us don't shoot in vastly different locations with any frequency. The effects of weather and the environment don't play a signifcant role in our ranging or sight adjustments. But the effects of environmental and meteorlogical (ENV/MET) variables can have a drastic effect on POI when the location changes dramatically. Most of the ballistic tables are prepared around Standard Atmospheric Conditions (SAC): 59.5 degrees F, Barometric Pressure of 29.92in Hg, 0% Humidity, and 0ft ASL. At short range (100 - 600yds), the effects of different ENV/MET variables aren't that important and can be neglected. And, depending on the caliber, even at ranges out to 1000yds the change isn't that great. But it can add up and change your POI considerably.
As with mirage, there aren't any hard, fast rules but there are guidelines: Temp up / sights down...Humidity up / sights down...Baro P up / sights up.
Exercise I-B
-Using the data from Shooting Exercise I (mine/yours..irrelevant: Sierra .308cal 150gr FMJBT, BC of 0.226, MV of 2740fps) and ANY OTHER SOURCES, what are
A) The elevation for 800, 900, 1000 yards at SAC
B) ..at 95 degrees
C) ...at 85% humidity
D)...at 30.35 in Hg
E) all of the above combined
F) Why, when you correct for Barometric Pressure, you simultaneously correct for altitude?
S.
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