[Airdale]

You all prolly know about this but if you don't and you have a mildot scope this would really help with these kind of calculations.
http://www.midwayusa.com/viewProduct/?productNumber=131691

 

[JLA]

Nope. Try running that by a math or physics prof at your local college.

Jim

Ima busy man.. would you care to elaborate a bit? If theres an unforseen hole in my logic I would like to have it pointed out to me so I can learn the correction. I have run the numbers backward and forward and fail to see how it wont work, afterall a triangle is a triangle whether its graphed on paper or 3 points between you, the base of a hill and the deer on the hill.. Save me the time of seeking a college prof and wasting his time. Hes got kids to teach..

 

[Jim K]

Nevermind, I am too busy to even think about all the false assumptions, but try this one. How does your system deal with the various trajectories for different ammunition?

Jim

 

[JLA]

it doesnt. it simply defines the distance the bullet is affected by gravity, the trajectory of a given round calculation is still made using the ballistics of the cartridge you are shooting.

Multiplying the line of sight by the cosine of the angle only gives you the hold over distance. It is up to you to adjust your optics for the holdover distance with the information on your range card for your rifle and ammo.

Therefore the this method of calculating holdover is viable for any shooting system in any caliber.

 

[JLA]

It would be exceptionally useful shooting squirrels out of trees from a sitting bench with a .22LR. so long as you have your .22 range card handy and know its trajectory out to say 150 yds, you can use this system to determine the adjacent and make better shots on the more distant tree rats.

 

[Jim K]

Deleted

 

[JLA]

deleted?

 

[JLA]

"The cosine has no connection with gravity. All your formula gives you is a number, which may or may not relate to the holdover distance, the cubic centimeters of my car's engine, or the length of the king's foot. Or something."

Ill try to explain this more clearly..

When you shoot over an angle, up or down hill is irrelevant, you have a line of sight to the target.. Laser that range and you have a number, that number is the Hypotenuse of the triangle.. Multiply that number by the cosine of the angle your are shooting over, again up or down hill is irrelevant, and it will give you the length of the adjacent, or in this case the distance the bullet will be affected by gravity.. plug that distance into your range calculations instead of your 'hypotenuse' range and your bullets will hit the target instead of flying over it. This is about as simple as I can explain it. It makes absolute perfect sense in my head.

In response to the quote.. The cosine of the angle youre shooting over, when multiplied by the ranged line of sight gives you the range you should calculate your trajectory for, in other words IT IS THE HOLDOVER DISTANCE. simple as that. It has absolutely nothingh to do with the size of an engine or the length of a kings foot. That is just silly..

 

[JLA]

Forgot one more thing...

No the cosine does not have any connection with gravity whatsoever. Not once in any of my posts in this thread does it say that it does. I have proofread ALL of them and corrected mistakes (save for some spelling) and re-worded things to make them more easily grasped because I know sometimes, something will make absolutely perfect sense in my head but when I try to explain it nobody understands. Thats been the story of my life my entire life.

Again, to re-itterate, the cosine of the angle you are shooting over, when multiplied by the measured line of sight to the target will give you the holdover distance correct for calculating the proper ballistics to achieve a hit on target and nothing more. Its just mathematics, I wont call it simple math, but then again i have looked at some advanced formulas and equations and said YIKES! WTF, wheres the door...

 

[Jim K]

(Goofed on the delete and wanted to keep the order right so I just left it there, sorry.)

Now, you write

"it doesnt. it simply defines the distance the bullet is affected by gravity... multiplying the line of sight by the cosine of the angle only gives you the hold over distance."

How does the cosine incorporate gravity? As for "the distance the bullet is affected by gravity", when, pray tell, is the bullet NOT affected by gravity between the end of the barrel and the time it strikes something? The figure you arrive at is a number; it could equal the holdover distance, or the number of CC's in my car's engine, or the number of beans in a can, or something.

You give the whole thing away by saying that, "the trajectory of a given round calculation is still made using the ballistics of the cartridge you are shooting." Bullet drop figures are included in most balistic tables and can be calculated by some very complex formulae, but not the way you have tried to do it.

Your calculation produces nothing.

Jim

 

[Country101]

EEEKK! MATH!

 

[JLA]

Youre not understanding Jim..

The cosine of the angle does not incorporate gravity. the distance youre shooting over incorporates gravity. The cosine is used to figure the distance the bullet is affected by gravity and nothing more, because when you shoot over an angle, the line of sight distance is longer than the distance the bullet is affected by gravity. Which is why you aim low when shooting at something up or down hill instead of holding center like you normally would if you were shooting a level line of sight.

Here I just spent the last 15 minutes making a drawing in paint so maybe I can help you to understand..

 

[JLA]

Refer to the drawing above...

The line of sight is the distance between the hunter and the deer, figure c (Hypotenuse of triangle) which is 300 yds...

The distance the bullet is affected by gravity is the adjacent, figure b...

You calculate this figure using what you know.. The lasered distance to the target (figure c) and the angle your shooting over (either estimated or measured with a shooting square) to arrive at the angles cosine using the chart in the link in my first post.

Figure b, the distance the bullet is affected by gravity would be unchanged if the deer and hunter swapped places. the bullet must travel that distance no matter the direction it shot in (up or down hill) that is why this calculation is relevant to shoting over angles.

The average MV of modern cartridges is roughly 3000 fps. A bullet is going to travel 300 yds (900 feet) in 1/3 of a second which is the same time it takes the bullet to travel the 245.73 yds of the adjacent at the angle you shoot it at...

I really cant make it any plainer. I really hope this helps you understand..

 

[H-D]

Finally!!!! a picture thanks the stick man and deer helped too .I finally got what you were saying, the bullet travels the full 300 yards but since elevation has no difference on the gravity , the bullet drops the same amount (due to gravity) that it would in only 243.75 yds because that is the lateral distance from you to the target..whew

 

[JLA]

EXACTLY. stickman always works..

I wish theyd put stick figure drawings in all advanced math books..

 

[bluesea112]

I thought these calculations became a mute point with the invention of the laser range finder.

 

[JLA]

No, the laser range finder provides a quick, simple and accurate means of measuring the line of sight to the target.

 

[JLA]

I was thinking about this thread today while driving back from the deer lease and it hit me. People that would use this kind of math to calculate proper holdover would be bowhunters in a treestand.

We all know a bow and arrow has a rainbow trajectory over a relatively short distance, and a miscalculation of as little as 5 yards can result in a miss. Sometimes a big miss if the range is longer than average. A bowhunter 30 feet or so up in a treestand with a deer in his sights will need to know precise holdover so he doesnt watch his arrow graze the top of the deer. This formula of multiplying the line of sight by the cosine of the angle to determine correct holdover would help bowhunters most I think.

 

[Jim K]

Nice drawing. But the flight path of the bullet is always GREATER than the line of sight to the point of impact, because the bullet travels in a parabolic curve, no matter whether one is firing on the level, or up hill, or down hill. Since the bullet is "affected by gravity" from the time it leaves the muzzle until it strikes something that stops it, it is "affected by gravity" for its entire flight path.

Jim

 

[JLA]

cant disagree with any of that Jim. It is all correct. But the math posted above for the last 2 pages is still accurate and still applies to shooting firearms, bows, slingshots, etc. etc. etc over any angle.

Just because you dont understand why something works or how something works doesnt mean it doesnt work. Perhaps it would be easier for you to think of it as an unexplainable shooting phenomenon and leave it at that. Because I really cant simplify what im trying to explain anymore than I already have.

Just trust that if you ever find yourself shooting downhill at a 300 yd target over a 35* angle, I promise you if you shoot at the target like its 246 yds away instead of 300 your bullet will hit it where the crosshairs lay. Shoot for the full 300 yd distance and your bullet will fly high.