Home Forums Hunting & Shooting Ask The Gunwriters POI vs. Inclination

I have a new Rossi M92 in 44 Mag. I'll probably be able to get a 240 grain jacketed bullet up around 1800 fps and a lead bullet up around 1300fps (just guessing, don't hold me to it.) It got me to thinking about how elevation is going to affect point of aim. I know we've talked about this before. I know a bullet fired from a treestand hits higher than one fired from the ground, and the same is true if you're shooting up hill.

This got me to thinking further. When I sight in my deer rifles on the front porch, the 100-yard target stand is well below the elevation of the house. I'm going to estimate 20 feet or more. I normally sight in my deer rifles at +2" at 100 yards, and it has served me well over the years. I never hit high or low out beyond 200 yards, which is the furthest I can shoot on the property anyway.

My question is this: how does one quantify the effect of inclination to the target ? The last time I had to do this sort of calculation, they were making me use a slide rule.

Cosine of the angle times the distance.


Or the simple way is to use a range finder.

https://www.sierrabullets.com/exterior-ballistics/3-3-effects-of-shooting-uphill-or-downhill/

Scroll down a bit, they discuss the .44 Mag with stats.

The closer you get to vertical (100% slope), the less affect on trajectory. My guess is that a 6+% slope(20 ft. in 300) won't have enough affect on the trajectory at 100 yd. to compensate for.

Here's a link to a good explanation of how that works:

https://www.rifleshootermag.com/editorial/hitting-a-high-or-low-angle-shot/83768

Not enough to worry about. If you were shooting at 400 yards at a target 100 yards higher or lower than you then it's something to account for. This is actually more of a concern for archery hunters 30' up in a tree shooting an arrow at a deer 30 yards away.

The effect of gravity is what we are overcoming with the flight of a projectile.

The effect of gravity on a projectile is perpendicular to overall curvature of the earth, not perpendicular to the slope of the shot.

For perspective, if you are on a cliff 400 feet above your target, and your target is 300 feet from the base of the cliff, your line of sight, and the distance your projectile travels would be 500 feet....but the effect of gravity on the projectile would only be 300 feet. Without understanding that you would assume your sighting would require compensation for 500 feet, and you would hit high.

To answer your question, the easiest is to just use a range finder with angle compensation software on board. I just bought one from Doug, very reasonably priced.

This was the answer I was hoping for.

JMR is usually spot on..