I have had this question rolling around in the back of my mind for quite some time, and this weekend, I awoke thinking of it again as I was about to head to the range to sight in a couple new rifles and test out some new ammunition in a couple of other...
What is the actual impact on a bullet's flight due to changes in temperature and elevation when hunting?
Well, it took me most of the weekend to crunch the numbers, but for some of my more common cartridges used for hunting, in my region, and the various elevations I have hunted, and the average monthly temperatures in which I hunt, here are the answers to my question:
Over the past 38 years of hunting big game, I have taken 119 animals, in what I will call the flat lands and the mountains, at distances ranging from 5 to 475 yards. The average shot distance has been132 yards.
The elevations I have taken game at ranges from 2200 to 6000' ASL. The average is at 3200' ASL. (The average flat land elevation has been 2600' (61% of game taken) and 4400' (39% of game taken) for the mountains.)
The temperatures in the areas I have hunted has ranged from approx. -30 degrees below zero to approx. 30 degrees Celsius above zero. The average monthly temperatures have ranged from -6 degrees C (21 F) below zero in November to 27 degrees C (80 F) above zero in August, withe an average of 6 degrees C (43 degrees F).
I have been using 2200' ASL in the Hornady Ballistics Calculator, and a temperature of 10 degrees C (50 F) to calculate the ballistics of various cartridges (chronied and factory spec velocities) for quite some time now. I use a 200 yard zero, and 100 yard increments out to 500 yards (the distance I can shoot at my range for practice), and therefore my limit for shots on wounded game if needed. Of all the game taken to date, I have less than a handful of game taken at over 400 yards. (The longest shot was under estimated at the shot, and verified afterwards).
I looked at 7 different cartridges that many use today for hunting, and chose the ones using the new Federal Terminal Ascent ammo just so I had a consistent hunting bullet for comparison. These include the following: 6.5 CM, 6.5 PRC, 270 Win, 270 WSM, 7mm Rem Mag, 7MM PRC and 300 WSM.
The variance of drops in elevation from my usual calculation of 2200' and 50 F, ranges from 1.6" to 2.8" at 500 yards!
Variances of drops @ 500 yards, from 2600 to 4400' ASL and 21 to 80 F, using the 200 yard zero is:
-6.5 CM 130 gr(24" barrel) is 2.4"
- 6.5 PRC 130 gr (24" barrel) is 2"
-270 Win 136 gr (20" barrel) is 2.8"
-270 WSM 136 gr (23" barrel) is 1.9"
-7mm Rem Mag 155 gr (26" barrel) is 1.6"
-7MM PRC 170 gr (24" barrel) is 1.7"
-300 WSM 200 gr (23.5" barrel() is 2"
Not as big a variance in drops as I might have imagined! (And of course, the variance is less for 400 yards, my self imposed limit today.)
And I know that my shooting is not such that I am going to see that big a difference at this range, especially since I do not shoot at unwounded game at 500 yards anyways.
Moving forward, I will be using 3200' ASL and 43 F for my Hornady Ballistics Calculator when calculating, as that averages out with the ballistics of these cartridges in my rifles for the game I hunt, in the months and locations I hunt, in order to give me the closest overall average drops for sighting in and shooting, to effectively take game in the places I hunt regularly.
Have any of you looked at this for what you shoot, and where/when you hunt?
What is the actual impact on a bullet's flight due to changes in temperature and elevation when hunting?
Well, it took me most of the weekend to crunch the numbers, but for some of my more common cartridges used for hunting, in my region, and the various elevations I have hunted, and the average monthly temperatures in which I hunt, here are the answers to my question:
Over the past 38 years of hunting big game, I have taken 119 animals, in what I will call the flat lands and the mountains, at distances ranging from 5 to 475 yards. The average shot distance has been132 yards.
The elevations I have taken game at ranges from 2200 to 6000' ASL. The average is at 3200' ASL. (The average flat land elevation has been 2600' (61% of game taken) and 4400' (39% of game taken) for the mountains.)
The temperatures in the areas I have hunted has ranged from approx. -30 degrees below zero to approx. 30 degrees Celsius above zero. The average monthly temperatures have ranged from -6 degrees C (21 F) below zero in November to 27 degrees C (80 F) above zero in August, withe an average of 6 degrees C (43 degrees F).
I have been using 2200' ASL in the Hornady Ballistics Calculator, and a temperature of 10 degrees C (50 F) to calculate the ballistics of various cartridges (chronied and factory spec velocities) for quite some time now. I use a 200 yard zero, and 100 yard increments out to 500 yards (the distance I can shoot at my range for practice), and therefore my limit for shots on wounded game if needed. Of all the game taken to date, I have less than a handful of game taken at over 400 yards. (The longest shot was under estimated at the shot, and verified afterwards).
I looked at 7 different cartridges that many use today for hunting, and chose the ones using the new Federal Terminal Ascent ammo just so I had a consistent hunting bullet for comparison. These include the following: 6.5 CM, 6.5 PRC, 270 Win, 270 WSM, 7mm Rem Mag, 7MM PRC and 300 WSM.
The variance of drops in elevation from my usual calculation of 2200' and 50 F, ranges from 1.6" to 2.8" at 500 yards!
Variances of drops @ 500 yards, from 2600 to 4400' ASL and 21 to 80 F, using the 200 yard zero is:
-6.5 CM 130 gr(24" barrel) is 2.4"
- 6.5 PRC 130 gr (24" barrel) is 2"
-270 Win 136 gr (20" barrel) is 2.8"
-270 WSM 136 gr (23" barrel) is 1.9"
-7mm Rem Mag 155 gr (26" barrel) is 1.6"
-7MM PRC 170 gr (24" barrel) is 1.7"
-300 WSM 200 gr (23.5" barrel() is 2"
Not as big a variance in drops as I might have imagined! (And of course, the variance is less for 400 yards, my self imposed limit today.)
And I know that my shooting is not such that I am going to see that big a difference at this range, especially since I do not shoot at unwounded game at 500 yards anyways.
Moving forward, I will be using 3200' ASL and 43 F for my Hornady Ballistics Calculator when calculating, as that averages out with the ballistics of these cartridges in my rifles for the game I hunt, in the months and locations I hunt, in order to give me the closest overall average drops for sighting in and shooting, to effectively take game in the places I hunt regularly.
Have any of you looked at this for what you shoot, and where/when you hunt?
