Angle Shooting - Correcting For The Effects Of Gravity by Ward Brien

[Len Backus]

Think of the direction of gravity towards the center of the earth. As the target angle changes, the angle of gravity stays the same. Less of gravity's force comes into play. I agree that time stays the same but the gravity VECTOR (fancy first year college physics term) changes relative to the angle of the shot.

Gotta go bowhunting now.... gun)

 

[MontanaRifleman]

Jaceduece, Like Len said it's the *vector* (direction) of the force of gravity that is changing (in relation to the bullet's path, not the Earth) when changing shooting angle. The force of the gravity IS the same over the same period of time. But the percieved affect (drop) is different becausse that effect is no longer perpendicular to the bullet's path.

To take it to an extreme, if you shot a bullet straight up, there would be no percieved drop at all, because the bullet hasn't traveled over ground at all. But... gravity has still had an affect on the bullet. The more you increase the angle up (or down) the less the *percieved* effect in relation to the level ground because less level ground has been covered in the same amount of time. Now, imagine the shot that is almost straight up, say 80 degrees, still almost no percieved drop, but gravity is still working. The more you angle your shot toward the earth, the more you see the results fo the gravity pulling the bullet down from it's path.

Hope that's clear as mud.

 

[Marine sniper]

Also consider when shooting uphill v. downhill, that gravity has far less effect on the bullet than drag (resistance to air) so while gravity may pull a little harder on a bullet going uphill it is negated by the effect of drag.

 

[jwp475]

Also consider when shooting uphill v. downhill, that gravity has far less effect on the bullet than drag (resistance to air) so while gravity may pull a little harder on a bullet going uphill it is negated by the effect of drag.

Exactly. There is much more to than just gravity

 

[deepandsilence]

.308 Tactical (Custom Built) : Bolt Action at GunBroker.com
Check out my rig, I got one of those angle finders from Night Force and I am thankful for it. 617 yards one shot cold bore hit down hill almost at 45 degrees.
Target milk jug.
Mission accomplished.
I use Eskimo for ballistic calculations and weather channel for data.
Works just fine!
deepandsilence

 

[eshell]

Great article Ward!

I have several (5) of these ACI's on my various competition and hunting rifles and have been VERY pleased with both the device itself and with Ward's first class customer service. I damaged one myself and could not have asked for a faster or more generous solution than that offered by Sniper Tools.

 

[japhunter]

I have been having trouble matching ballistic software results to the real tradjectory measured . I am in the proccess of going througn the many obvious varailbles but i am now wondering weather there is some correction for having a 20 moa one picatiny rail that i should be making ?
Regrds Jap Hunter NZ

 

[Eaglet]

I have been having trouble matching ballistic software results to the real tradjectory measured . I am in the proccess of going througn the many obvious varailbles but i am now wondering weather there is some correction for having a 20 moa one picatiny rail that i should be making ?
Regrds Jap Hunter NZ

japhunter,

The 20 MOA rail all it does is help for the Vertical adjustment, it won't mess you up with matching your software trajectories.

 

[cdoubleu]

Jap Hunter,
If you are having problems matching your trajectory these will be your biggest obstacles: Accurate muzzle velocity (backwards calculated from chronographed speed, and distance measured from the barrel), An accurate BC (not necessarily listed), and finally, insuring that your scope's click value is actually what it is advertised as. To check the adjustment value, zero your rifle at 100y/100m what ever you use as a standard, pick an aim point at the bottom of the target and in half or full turret revolutions verify the distance between group centers exactly what they should be in click values. Example: @100yds, 1MOA=1.047", change vertical adjustment up 10MOA=10.47", fire a group, hopefully your group is 10.5" high. This may take a tall target depending about your scope's elevation abilities, but an appropriate target (hung vertically with a plumb bob) will tell you wonders about your scope.
As previously mentioned, the difference of 1/3 of a degree of angle (20MOA) isn't going to make a noticiable difference in trajectory, even at 1000yds it's much smaller than even the best are able to shoot. You wouldn't be able to correct for it either because it is less than one click value on 0.25MOA or .1MIL adjustment scopes.

 

[HUAINAMACHERO]

Just read the article. Very educating, thanks for it. Will be purchasing a ACI and mounting system soon!!!

 

[WyoElk2Hunt]

Good article

 

[bronc]

i have a question, maybe yal can help out
i understand correction for angle shooting, i am unclear if you use that correction for wind age adjustment as well
ie
i have the same shooting situation as in Ward Brien article
500 yard shoot
at 30 angle
lets say my my correction for 500 yard is 7 moa, so i take 7moa * .87 (cosign of 30)
= 6.09 moa is what i dial in on my scope

what iam asking is do you also do the same for windage adjustment
ie
lets say same shoot as above but have a 2moa adjustment for wind
would i take 2 moa * .87(cosign of 30) = 1.74 moa that i dial on my scope for wind adjustment?
gun)

 

[paphil]

Use the wind value for the full 500 yards.

 

[Aviator]

Very good read ! but doesn`t the new rangefinders with angle compensation do all the math for you ? minus the wind, temp. and barometer calculations..