bullet drop at altitude?

D

d2admin

Administrator
i am in need of information regarding bullet drop. i have a friend who will be hunting elk in co this fall, he insists that bullet drop is less of an issue in higher elevations. i have no idea, in theory, i would think gravity is the main function, not air denisity, but i want to make sure. any help would be appreciated
 
Buck GU,
Bullet drop is indeed (significantly) less at higher altitudes. The Federal web site has some software you can get for free that will demonstrate it.

Dawgkilla

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Tree hugger?
Um, .... NO.
 
Yes, gravity is a little less, atmosphere is a little thinner, so trajectory is a little flatter.

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Critr

LW42144.jpg

www.SaguaroSafaris.com
 
The difference in gravity, unless you go into orbit is totally insignificant.

At higher altitudes, the thinner air has a major effect on trajectory, and retained velocity, and energy, at the longer ranges.

If you run the numbers thru a ballistics program, it may suprise you what a difference altitude can make.
 
So seeing how I am in Montana if I sight my rifle in at 1/2 inch high at 100 yards and I am getting 3900fps plus I am using the max powder load. Now I go to California and shoot the exact same load at a 100 yards I would hit right on at a 100 yards what happens to my velocity would it increase at lower elevations and would I run into trouble with my max load or is it the other way around?(just an example I don't know how major the effect is really)

Thanks
Shawn
 
Shawn
At the closer ranges there is not a big effect. At long(beyond 500 yards) ranges the difference is dramatic.

I ran the numbers for a Sierra 55gr SBT at 3900 fps for an elevation of 20 feet and 7000 feet, out to 500 yards.

At 100 yards there is only 0.1" difference in trajectory and the bullet has slowed down 73fps more at 20 feet than at 7000.

At 500 yards the difference is getting larger. For the rifle sighted in at 100 yards the bullet will hit 28.8" low at 20' and 25.3" low at 7000'. When we compare remaining velocity and energy, there is now a big difference. The bullet fired at 20' has slowed down to 2168fps and 574 ft-lbs of energy. The one fired at 7000' has slowed to 2504 fps and has 766 ft-lbs of energy. A 5mph wind moves the bullet at 20' 11.3 inches and the one at 7000' 8.4 inches.

Beyond 500 yards the difference becomes more dramatic.

Altitude has no measurable effect on load pressure, assuming similar temperatures.
 
About twenty years ago, I was pretty sure that my gun was where I wanted it. That's in California @ 1000 feet elevation.However, almost the first thing I did when arriving in Colorado was check the zero and was surprised that it was shooting about 4½ inches higher than the day before. Sitting in a rifle rack, the whole time. As I recall the elevation was probably about 8,000 feet. Since then, I ALWAYS check it out.

There is another condition to be concerned with, and it is the ambient temperature. It was balmy in California, and downright nippy in Colorado. Therefore; it pays to assume nothing. Jack gives some very good data, good to know. But don't just run the numbers, put a couple holes in paper (not a road sign) and you will sally forth with confidence. That's my story, and I'm sticking to it.

Good hunting. LB
 
Every year here in New Mexico we host a major baseball tornament for 17-18 yr old ball players. They come from all over the US and a few teams from Puerto Rico. All of these eastern players make the comment on how much further they hit the beaseball. Thinner air equals less drag.

I love to drag race, and being at a mile high elevation we lose 20% of power due to the air. You lose some you win some, seems to even out a bit.?

Chad
 
gravity is in fact a constant when factoring for any physical equation, the key elements are temp and altitude. as you increase the range from 500 yards these become more important. i have to thank an old physics prof. from clarion univ of pa for his help. Buck GU
 
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