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# Shooting uphill or downhill

robert574
Member Posts:

**223**✭✭✭
I know this has surely been discussed many times before, but I just purchased a laser rangefinder and I was also playing with some ballistics software I had downloaded comparing rounds. The software is Remington "Shoot" and it does not allow for anything except a horizontal shot.

Here is my thinking about the angled shot.

If I sight in my 270 at 300 yards at the range, then stand at a hillside and place a target a true distance of 300 yards up the hill (we can verify the distance with the rangefinder), the shot should be on target.

The bullet is being pulled down by gravity over the time that it takes it to leave the barrel and strike the target. Gravity is constant. If I fire 300 yards uphill or 300 yards horizontally will the time be different?

I read a couple of articles that suggest shooting high or low (can't remember which one).

Does anyone have some ballistics software installed that allows for adjusting target height?

Does anyone know the ballistics formula (with an angle) that also uses the ballistics coeficient of the bullet?

Thanks, Bob

Here is my thinking about the angled shot.

If I sight in my 270 at 300 yards at the range, then stand at a hillside and place a target a true distance of 300 yards up the hill (we can verify the distance with the rangefinder), the shot should be on target.

The bullet is being pulled down by gravity over the time that it takes it to leave the barrel and strike the target. Gravity is constant. If I fire 300 yards uphill or 300 yards horizontally will the time be different?

I read a couple of articles that suggest shooting high or low (can't remember which one).

Does anyone have some ballistics software installed that allows for adjusting target height?

Does anyone know the ballistics formula (with an angle) that also uses the ballistics coeficient of the bullet?

Thanks, Bob

## Comments

618✭✭✭13,451✭✭✭This will vary depending on the degrees of angle from horizontal.

I dont have tables for this but, for example if you shoot straight up or straight down, there will be no "sideways" pull of gravity on the bullet so there will be no "drop".

Theoretically, if you shoot a bullet up at a 45 degree angle it will drop about half of what it would, at a given distance, than if shot level.

Bullets shot level will have max gravity pull when compared to bullets shot up or down at varied angles.

10,928✭✭✭✭When a gun is sighted in on a level or nearly level range and then is fired either uphill or downhill, the gun will always shoot high. This effect is well known among shooters, particularly hunters, but how high the gun will shoot is a subject of considerable controversy in the shooting literature. In fact, at the present time some literature has information that is simply erroneous. In this subsection, we will try to explain the physical situation carefully so that it can be understood clearly, and then provide some examples using Infinity to perform precise calculations.

http://www.exteriorballistics.com/ebexplained/5th/33.cfm

http://www.wildsheep.org/magazines/article_uphill_shooting.htm

Uphill-Downhill Shooting

Shooting uphill or downhill will result in high shots if the angle is roughly 15 degrees or more or if the range is very long for lesser angles. The actual bullet drop is dependant on the true horizontal distance to the target not the slant range. Our range finders measure the slant range. Again there are several methods to determine the amount of correction necessary. Most, if not all, ballistic programs can take into account angled shooting and print out the correct drop for any range. The Sierra handloading manual in the exterior ballistics section deals with this subject with an example.

The Sierra manual has a table of factors that in use are multiplied by the total drop in inches, for the slant range to the target. The factors are .034 for 15 degrees, .134 for 30 degrees, and .293 for 45 degrees. There are more listed in the manual but these will give the reader an idea of the degree of change as the slope increases. Their use is simple. Let's say that you were looking uphill at a mule deer buck that your range finder said was 675 yards away. Looking at your drop chart you read that for that distance you need 11 1/2 minutes of adjustment in your scope. The catch though is the buck is uphill at an angle of 30 degrees. Using these factors we take the total drop for 675 yards (which is 103.1 inches) and multiply by .134 (the factor for 30 degrees) and the result is 13.8. That is to say that the bullet would impact about 14 inches high if we did not allow for the angle. Fourteen inches is about two minutes of angle at that distance. From this example we can see that it would be easy to miss that buck had we not taken into account the steep angle to the deer.

http://www.riflebarrels.com/articles/longrange_shooting/shooting_hunting_page2.htm

http://www.snipersparadise.com/ELR/reverse.htm

Best.

44,719✭✭✭http://www.gunsandammomag.com/gun_columns/notes/gn0409/

7,734✭✭The drop due to gravity however will change, as gravity only works over the "horizontal" portion of the bullets path. Break out your calculator and multiply the sin of the angle by the measured distance to calculate the bullets horizontal range. Example: 300yd at a 45^ angle (up or down) will have the same drop as a flat shot at 212yd.

271✭✭8,595✭✭✭223✭✭✭For example #1, let's say you have a target that is 100 yards in front of you and 300 yards high. Let's ssy some idot with a rifle shooting from the top of your local office building otherwise I would never shoot over a hill even hunting. (A mountain side maybe but we don't have any in Florida).

For example #2, let's say you are shooting at the range at a similar distance horizontally.

I kept the time constant because I thought it would control the drop the same. Here were the results of a 3000 ft/sec muzzle vel (without considering ballistic coefficients, air, etc. (hope the numbers stay stratight)

flight time (sec) 0.3167 0.3167 sec

muzzle vel (ft/s) 3000 3000 ft/s

angle (deg) 71.60 4.00 deg

muzzle vel horiz (Vox) 947 2993 ft/s

muzzle vel vert (Voy) 2847 209 ft/s

Horizontal dist 300.00 947.90 ft

Vert distance 900.00 64.67 ft

distance to target 948.68 950.10 ft

Horizontal vel 947 2993 ft/s

Vertical vel 2836 199 ft/s

velocity 2990 2999 ft/s

The point is that if you had to take this shot it looks like the distance traveled during the exact same time would be slightly less, the muzzle velocity at the target would be slighly less and I would expect that a high velocity round would hit slightly below the mark, but not much on the elevated target.

It would depend of course on the round and that you were still on a relatively straight part of it's trajectory.

I've heard people say that you would shoot high with this shot, but it doesn't make sense.

The article is sort of confusing also.

Anyone know for a fact what happens?

223✭✭✭Thanks for your replies. I'll check out the other links and read up. They all seem to agree that the shot will be high. Over 500 yards is a long shot. Maybe the fast drop causes it at long distances.

I left all of my calculations in feet. The 300 ft x 900 ft calc was the 100 x 300 yard elevation.

223✭✭✭This table calculates the horizontal distance to target. I guess this is the only component where gravity acts to cause drop.

In my example of an elevated target 100 yards horiz and 300 yards high, I would need to use a sight zero of 100 yards and not the distance to target of 316 yards.

hmmm...interesting