BULLET RISE

CryptoChief

Going on a hunt this year out West. Elevation where I am sighting in my rifle(s) is 900 feet above sea level. Hunting elevation will be between 5000 and 6000 ft. Have heard, not from any specific source, that bullets will impact approximately one inch high for each 1000 feet of elevation. Any documented info out there to this phenomenon?

CC

Rocky Raab

I think that's grossly exaggerated. In theory, the less dense air will have an effect on trajectory due to reduced drag. But nowhere near the numbers mentioned.

Here's my basic rule for sorting this kind of thing out: If the change is less than the space covered by my scope crosshair at the range I'm shooting, there is no change.

JustC

I live at sea level, my rifle when fired at the target in WY was still right where I needed it to be. I didn't even see an inch variance.

glabray

The Lyman 47th Reloading Manual covers this in a lot of detail. Unless you will be shooting at more than about 400 yards, the effect of lower air density at elevation is quite small. For example, Table 10 in the Lyman manual shows that for a 30-06 180 grain bullet with a muzzle velocity of 2700fps, being fired at a target 300 yards away, at 5000 feet the POI is only 0.60 inches above that at 500 feet elevation. If this will be your first time hunting out here in our western mountains, you need to be aware of the effect of higher POI when shooting uphill or downhill. The Lyman manual shows for that same situation, a POI 0.83 inches high if firing on a 15 degree slope and 3.24 inches high if the slope is 30 degrees.

Odawgp

I don't have any documentation

Our Range offers "Sight in Days"

In which we allow hunters from all over the country that are coming here to hunt big game, to come out and check their rifles before going hunting.

90% of the guys that had previously sighted in 1" high @ 100yds below 1000ft get here (8000ft) and have to adjust their sights n scopes down some as much as 2 - 2.5" most are shooting 1 1.5 higher when they get here

Of course this is hear say do to the fact that I wasn't there when they did the first sight in

Where are you going what state county ect...?

CryptoChief

Will be going to Idaho. Grangeville to be exact. Selway Bitteroot area. Camp at 3500 ft. with hunting at 5000 to 6000.

I guess there is a little truth to the bullet rise issue but it seems to be blown out of proportion when traced back to conversations I have had with some "friends". And it makes sense that the seemingly most important factor is and always will be, gravity.

All the feedback has been great. I very much appreciate what has been offered. It certainly puts to rest any fears I may have had. Sure would hate to miss my chance at an elk or muley because of some "wrong thinking". Thanks guys.

CC

sandwarrior

CryptoChief,

The bullet rise theory isn't really blown out of proportion, it's just not applicable to the shorter ranges that most people shoot while hunting. Out to 300 yds. it will make about 1/2" -1" difference. That will probably be set off by a lower temperature. It's when you get beyond 300-400 yds.that that it makes big difference.

Try going here: http://www.eskimo.com/~jbm/calculations/traj/traj.html

It will give you a rough estimate of where you should be hitting.

As noted above one thing you are going to encounter out west is shooting uphill and downhill a lot more. You can change that on the "target angle" block. You have to remember that shooting uphill or downhill actually shortens the distance between you and your target. therefore the drop is less. Toy around with it and get some ideas as to where you will hit. Then if you can take your rifle out and duplicate what you can.

-good luck

CryptoChief

sandwarrior,

Thanks for the link. nononsense gave me one yesterday which was good. As far as the uphill and downhill shooting, I have an ARC range finder so I will be shooting the "correct" distance.

The scope I will be using on my primary rifle (30-338) will be pre-calibrated for bullet drop/wind deflection for the Idaho hunt, elevation and all else figured in. The glass on my back up rifle (7mag) on the other hand, will be standard fare. That's the scope/rifle set up I am gathering information on. I am guessing most of my shots, when they provide themselves, will be under that 300 yard mark so I should be safe either way.

I'll check out that link you gave me. Thanks again.

CC

dakotashooter2

It seems to be overated. Now it might make a considerable difference if your target is a woodchuck at 400 yards. But given a 10" vital area on most big game dead on is still gonna give you minute of kill at practical ranges. I suspect that in the field human error is a much bigger factor than elevation. Making the elevation issue seem bigger than it actually is.

m113103

Sight in when you arrive and listen to your guide. If you want you can goto an external ballistics program and plug in numbers. My RCBS load program will accept different parameters and overlay the graphs of the bullet paths.