Darryl Cassel
Well-Known Member
Hello
Most ballistic charts or programs have the humidity built in to the Barometric pressure, temperature and altitude.
Think of your high humid air as a "heavy, wet, thick air" that just hangs there as comparied to a dry thin air of low humidity that will rise when warmed.
The bullet , in my experiance and in different States, will drop more in the high humid air then it will in thin, clear, sunny air with less humidity.
From my understanding, there is less frontal resistance to the bullet in the dry, thin, air. More frontal resistance means the velocity loss will be greater.
Humid air hangs low and dry air rises with heat which, I believe was the comment by the sniper country site about upward air movement.
Upward air movement will cause the bullet to drop less.
For instance, when shooting at Williamsport in a 1000 yard match, lets say you shoot the first relay at 9AM when the temperature is a bit lower like 50 or 60 degrees. Leave all clicks the exact same as when you shot and shoot again at 2PM after the sun has warmed the ground to about 80 degrees and the heat waves are rising. Your bullet will be about 12" to 13" higher on the target then at 9AM.
When the temperture rises 20 or 30 degrees on a clear sunny day is when this happens .
You can run the same test at 500 yards also.
As far as the powder per each degree difference, don't really know as per brand of powder but, that is taken care of in the temperature programing at the start when you put the information in your ballistics program.
The velocity will increase or decrease with the temperature changes.
I don't think there would be that much difference between powders as per one degree temp change once you know your velocity "THAT DAY" and with any powder.
If H4831 is giving you 3000 FPS and H4350 is giving you 3050 FPS (That day) with the same bullet but a different charge, you can change the temp for either velocity and figure what that change is by your actual powder charge. Any good program will do this for you already. You can change your powder charge by one grain, chronagraph the speed and then program for one more degree up or down.
DC
[ 06-07-2002: Message edited by: Darryl Cassel ]
Most ballistic charts or programs have the humidity built in to the Barometric pressure, temperature and altitude.
Think of your high humid air as a "heavy, wet, thick air" that just hangs there as comparied to a dry thin air of low humidity that will rise when warmed.
The bullet , in my experiance and in different States, will drop more in the high humid air then it will in thin, clear, sunny air with less humidity.
From my understanding, there is less frontal resistance to the bullet in the dry, thin, air. More frontal resistance means the velocity loss will be greater.
Humid air hangs low and dry air rises with heat which, I believe was the comment by the sniper country site about upward air movement.
Upward air movement will cause the bullet to drop less.
For instance, when shooting at Williamsport in a 1000 yard match, lets say you shoot the first relay at 9AM when the temperature is a bit lower like 50 or 60 degrees. Leave all clicks the exact same as when you shot and shoot again at 2PM after the sun has warmed the ground to about 80 degrees and the heat waves are rising. Your bullet will be about 12" to 13" higher on the target then at 9AM.
When the temperture rises 20 or 30 degrees on a clear sunny day is when this happens .
You can run the same test at 500 yards also.
As far as the powder per each degree difference, don't really know as per brand of powder but, that is taken care of in the temperature programing at the start when you put the information in your ballistics program.
The velocity will increase or decrease with the temperature changes.
I don't think there would be that much difference between powders as per one degree temp change once you know your velocity "THAT DAY" and with any powder.
If H4831 is giving you 3000 FPS and H4350 is giving you 3050 FPS (That day) with the same bullet but a different charge, you can change the temp for either velocity and figure what that change is by your actual powder charge. Any good program will do this for you already. You can change your powder charge by one grain, chronagraph the speed and then program for one more degree up or down.
DC
[ 06-07-2002: Message edited by: Darryl Cassel ]