Shooting downhill math problem????

[6MMFAN]

Please help......

I am shooting at a target 350 yards away with my Rem. 6MM 90 grain bullet. I am shooting down hill. my rifle is zero'd at 100 yards and when I am on a level range I have to adjust + 6 inches (+24 clicks) to hit 350 but when shooting at this down hill target ;I only have to adjust +2 inches(+8 clicks).

Can anyone help me figuring out how much lower my target is from my shooting point and the angle.

Thank you

6

 

[DogBuster]

Try this........

http://www.millettsights.com/downloads/ShootingUphillAndDownhill.pdf

 

[brian427cobra]

Range the target, multiply that by the Cosine of the angle equals distance to target

 

[6MMFAN]

Range the target, multiply that by the Cosine of the angle equals distance to target

Range I know is 350 yards, but I do not know the angle ........

 

[brian427cobra]

http://www.slopedoper.com


And your also making a mistake in your scope adjustments, each click is 1/4 MOA.

 

[6MMFAN]

And your also making a mistake in your scope adjustments, each click is 1/4 MOA.
[/quote]


So if I adjust up 6 inches on the flat range. 6 X 4 = 24 clicks moa. How am I making a mistake there.

 

[M-61]

I do not see a problem with your math. What I would wonder are you sure of the range, both up AND downhill as being the same 350 yards?
Don't know if this would help as you seem to be questioning WHY the adjustments (number of 'clicks' 1/4 or 1/8/or 1/2 does not matter) change which actually they should not.
http://www.chuckhawks.com/shooting_uphill.htm

 

[brian427cobra]

Not knowing the exact bullet and speed from your weapon, I ran 90grn Nosler BT, 100 yard zero, going 2725 with a DA of 4000 and come up with 21.80 inches of drop and 5.95MOA come up for a 350 yard shot, as you can see the inches don't match up with MOAs, I used to do the same exact thing long ago, today I think in MOAs or MRADs when shooting, depending on my competition I use the correct tool to compete, MOA is a finer unit of adjustment and is best suited for group shooting with plenty of time, MRAD are a courser unit of adjustment and are perfect for fast shooting at variable distances with no time, so my recommendation is to stop with the inches and learn MOAs or MRADs, and no matter which system you choose, at any distance, 10 feet 100 yards, 76 lightyears, one click only moves the POI(point of impact) the stated distance, ie 1/4 MOA is 1/4 MOA at any distance

 

[mikecr]

6MMFAN, What is the specific bullet and your muzzle velocity?
And are the adjustments at 350 clicks or inches. Pick one for now.
The slope angle could be reverse calculated with pretty much any ballistic software.

 

[22BRGUY]

I believe what you are looking for is the actual horizontal distance you will be shooting. Gravity only pulls straight down over the horizontal distance. Think of a right triangle with you at the top angle and your target at the end of the bottom leg of the triangle opposite the right angle. You know the sloped leg of the triangle, which will be the longest, is 350 yards. Depending on how steep the angle is to the target will determine what your actual horizontal distance is to the target but it will always be less than 350 yards and that bottom leg of the triangle distance is what you need to use on your bullet drop chart to calculate how much drop the bullet will experience. Hope this helps

 

[Nomad47]

Your horizontal distance is approximately 210 yards. So if ranged yardage is 350, you have a severe downward angle. I will play with cosine angles for a bit and see what I come up with.

 

[Nomad47]

Your downward angle is ~53 degrees. That is 8 degrees lower than a 45 degree angle, which is about what stairs are. Like I said, a severe downward angle.

 

[22BRGUY]

If your actual horizontal distance is 210 yards, then that is the distance to look at for bullet drop because that is the only distance gravity can pull straight down on the bullet.

 

[6MMFAN]

6MMFAN, What is the specific bullet and your muzzle velocity?
And are the adjustments at 350 clicks or inches. Pick one for now.
The slope angle could be reverse calculated with pretty much any ballistic software.

I am using sierra .243 dia. (6mm) 90 gr. FMJBT at about 2400 fps

To hit 350 accurately on a flat range I need to make 24 clicks up witch equals 6 inches ( each click is 1/4 moa. ).
In order to hit 350 on the down angled range I need to adjust up 8 clicks witch equals 2"

 

[6MMFAN]

Your horizontal distance is approximately 210 yards. So if ranged yardage is 350, you have a severe downward angle. I will play with cosine angles for a bit and see what I come up with.

Your downward angle is ~53 degrees. That is 8 degrees lower than a 45 degree angle, which is about what stairs are. Like I said, a severe downward angle.

If your actual horizontal distance is 210 yards, then that is the distance to look at for bullet drop because that is the only distance gravity can pull straight down on the bullet.



Thank you all for your help , I appreciate it.

 

[mytwo60]

Doesn't matter how severe your angle is. At 350yds, you shouldn't have to adjust 4 MOA less. Something is wrong with your scope or your POI changed.


How in the heck are you only getting 2400fps with a 90grn bullet and only come up 6 MOA at 350dys?

 

[Nomad47]

Doesn't matter how severe your angle is. At 350yds, you shouldn't have to adjust 4 MOA less.

Wanna bet?

 

[Erik Cortina]

And your also making a mistake in your scope adjustments, each click is 1/4 MOA.

So if I adjust up 6 inches on the flat range. 6 X 4 = 24 clicks moa. How am I making a mistake there.

6mmFan, you are not adjusting 6 inches, you are adjusting 6 MOA. Also, get away from thinking in terms of "clicks" since it is a very inefficient way to adjust a scope.

 

[Nomad47]

Yes, by adjusting your scope up 6 MOA, you are accounting for ~21" (actually, 21 times 1.0472 or 21.99") of drop at 350 yards. Then adjusting it up 2 MOA, you are accounting for ~8" of drop at 350 yards. But with a downward (or upward) angle, you have to compensate for the HORIZONTAL distance the bullet travels.

 

[M-61]

This might help (from National Shooting Sports Foundation): (line#4 is key)




A Minute of Angle (MOA) is an angular measurement.

A MOA is 1/60th of a degree.

1 MOA spreads about 1" per 100 yards. (actually 1.047")

1 MOA is a different size at different distances, 8" at 800 yards is still just 1 MOA.

100 yds 200 yds 300 yds 400 yds 500 yds 600 yds 700 yds 800 yds
1" 2" 3" 4" 5" 6" 7" 8"