RE: Uphill / Downhill shooting
Excerpts from Peterson's Hunting, May/June 2004. Uphill, Downhill. The definitive word on an age-old debate. Pages 78-79.
"For most hunters, the mind's eye tells them that shooting uphill should cause a bullet to slow down quicker, drop quicker and therefore hit lower. When shooting downhill, it seems the opposite should occur: With gravity working in favor of the bullet, it should be going faster and hitting higher."
"But it's not the pull of gravity that's important - it's the angle of the bullet's path measured against the line of gravity's pull towards the center of the mass of the earth. The pull of gravity is perpendicular to the surface of the earth, so when you elevate the muzzle of your gun by X degrees, you are changing the angle of the bullet's trajectory respective to the line of gravity."
"Moreover, you are actually reducing the distance the bullet travels relative to the pull of gravity, compared to the same distance across a level surface. The effect of changing uphill or downhill angle on the bullet's path is therefore the same."
"So the path of the bullet always rises above the line of sight of a horizontally zeroed gun when you shoot at an angle either above or below the horizontal line. The greater the degree of the angle, the greater the amount of the rise. Not only that, but the amount of rise is exactly the same both for uphill and downhill shooting."
The article gives an example of a 30-06 150 grain cartridge fired at a 45 degree angle. At 300 yards it will about 7 inches higher than it would have on level ground.