Help on shooting from a tower.....

[Plank Road Farm]

My 30-06 is zeroed at 100 yds. on level ground.

Where do I hold on a target 175 yds. away shooting from an 18 ft. high tower?

Ammo is Federal Power-Shok 150 gr. soft point.

I'm not sure if I should shoot high or low.

Is there a formula for such questions?

TIA

 

[G27RR]

You would want to hold a bit low for both uphill or downhill slopes. There are formulas and quick check devices similar to a mildot master. You will need to know the angle of your slope, which you could figure out since you know the height of the tower and distance to target.

For 175 yds it may not matter all that much depending upon the size of the target.

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

 

[Owen]

18 ft elevation at 175 yards is an angle of less than 2 degrees. don't worry about the slope.

You need to know the height of your cope centerline above your bore centerline.

 

[dc.fireman]

Ummm... just outta curiosity... whatcha shootin' at?

 

[WNTFW]

I calculate that you are only .31 feet off @525 (175yds) feet being 18 ft high.
angle being 1.96 degrees.

If you know your drop for 175 vs 100 yds just use that.

 

[Shawn Dodson]

Don't worry about an 18 ft elevation. Shoot like you normally would at 175 yards for a rifle that's zeroed at 100 yards.

When shooting up or down a steep ravine or hill, you have to determine the "level" distance between you to the target. The angular distance will be farther than the "level" distance.

Consider a right angle triangle:


The angular distance is A - B but the "level" distance is A - C. Regardless of whether you're shooting uphill (A - B) or downhill (B - A), the "level" distance (A - C) is the same.

This is why a bullet appears to hit "high" when fired uphill or downhill. The "level" distance is the distance that gravity acts on the bullet.

 

[WNTFW]

http://www.slopedoper.com/purchaseSlopeDoper.html

This is a little device to measure angle to target and then get a factor to multiply range by.

 

[Mike J]

Here is a link to Federals ballistics chart for the cartridge you are using (if I got the right cartridge. http://www.federalpremium.com/products/details/rifle.aspx?id=16

 

[Plank Road Farm]

I am deer hunting.....

 

[S. Hill]

18 ft elevation at 175 yards is an angle of less than 2 degrees. don't worry about the slope.

What he said! Since you know that your target is 175 yds. away from your tower, you hold just like you would if you were shooting flat at 175 yds. The gravity affects the flight relative to that 175 yds.

Where it gets important is if you are shooting at a VERY steep down (or up) hill angle. An example - Your laser range finder says that it is 200 yds. to your target, but the HORIZONTAL DISTANCE is only 100 yds. If you held like you would for a 200 yd. shot, your bullet would strike high. Gravity has only acted on the projectile in the 100 horizontal yards.

 

[J.Boyette]

check it out,

The amount of degree under 20deg's is a non-pointer for offset. so do not worry about it.

My question to you is what is your hold for a 175yd shot with a 100yd ZERO?

 

[Owen]

like i said, you'll need to know your scope height above bore, and then, if your gun shoots at a similar velocity to the ammo on the mfg chart, just go by the chart.

 

[J.Boyette]

Owen,

That could work kind of.

A better way that is real easy to do at the range is to get 8" paper plates and set them out from 50yds to 250yds in 25yd increments.

Run the 100yd zero, aim center mass and shoot them with 1 round per plate

Once done look at the bullet placement. You will see that a 200yd zero will give you a better zero to shoot all the 8" plates and gain kill shots on a deer 8" kill zone.

I like to run on fact, not ideas.

 

[WNTFW]

Jboyette,
You will have guys calling your cell from deer stands.

Good point, in the first 20 degrees it is 6% max reduction in range.

 

[J.Boyette]

Wntfw,

 

[txhoghunter]

Is there a formula for such questions?

Yes there is and it starts with trigonometry.
I will refer to Shawn's figure here:

a^2 + b^2 = c^2 is how you determine the horizontal distance the bullet will travel (i.e. the distance that gravity will act on it and the distance you will adjust your POI for).

The weight of the bullet will not come into effect as long as you already know how much your bullet will drop when given a horizontal shooting distance from your trig calculations.

 

[GCBurner]

If you have an iPhone, there's probably an app for that.

 

[TonyAngel]

I use a little program that I got for my ipod. I just rest the ipod on the barrel, it reads the slope and then tells me what I have to dial in. LOL. I'm lazy and I suck at math.

 

[txhoghunter]

Yeah, knowing my trig is a bonus. I use the iphone app when I need a quick semi accurate educated guess

 

[J.Boyette]

guys,

Drop the I phones and get a Mil-Dot Master.

the only time the battery's die on it, is when your caffeine high wears off

 

[WNTFW]

All the country boys I know tell me "if you can hit the salt lick, you can hit the deer. You don't even need no math."

 

[J.Boyette]

WNTFW,

There is a level of truth to that.

 

[Art Eatman]

I'd advocate sighting in for two inches high at 100 yards. That's dead-on at 200 and about six inches low at 300. Saves a lot of worryin' and thinkin'. "Point it and pull; hell ain't half full."

Any angle less than twenty degrees or so needs no correction, up or down, for distances under 300 yards. Even at 45 degrees, the rifle thinks it's only 70% of the sight-line distance. Inside 200 yards? "Point it and pull."

Look at all the worryin' I saved ya.

 

[oldfool]

I estimate that anybody tuff enuff to live in Terlingua, Texas these days probably knows where any bullet is going to hit at any angle or distance !
(ipod or cellphone not req'd)

 

[KodiakBeer]

I'd advocate sighting in for two inches high at 100 yards. That's dead-on at 200 and about six inches low at 300. Saves a lot of worryin' and thinkin'. "Point it and pull; hell ain't half full."

Yeah! You people are over-thinking things a bit.