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Angle Shooting |
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supertool73
Optics God Superstool Joined: January/03/2008 Status: Offline Points: 11814 |
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Posted: May/01/2008 at 09:33 |
What are the physics behind angle shooting that makes it work the way it does. At a rifle class I took last weekend we discussed the math of how to do it and those things, but I did not feel like the physics behind how it works was explained very well. I don't think anyone really new, they just new it changes things and you have to do "this and this" to make hits.
Say you are shooting 600 yards at a 40 degree angle so you set the dope on your gun for 460 yards. Is it just the gravity is pulling the bullet different because of the slope? |
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cyborg
Optics God Gaseous Clay Joined: August/24/2007 Location: North Georgia Status: Offline Points: 12288 |
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The slope has less effect on the bullets density when shooting down or up hill than when shooting flat line, of course shooting up hill does increase the drag on the bullet as well so only up to a certain point will the math be the same as for shooting down slope.
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rkingston
Optics Apprentice Joined: February/29/2008 Location: Junction, Tx. Status: Offline Points: 97 |
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Think of it this way, the greater the angle away from horizontal, the less the bullet drop will be. Uphill / downhill has nothing to do with it. If you shot your rifle straight up in the air 500 yards or straight down 500 yards, the bullet drop would be zero.
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Dale Clifford
Optics Jedi Knight Joined: July/04/2004 Location: United States Status: Offline Points: 5087 |
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Is it just the gravity is pulling the bullet different because of the slope?
at - (downhill) inclinations the bullet seems to get there sooner, shorter distance less effect from gravity at + (uphill) inclinations it seems to take longer, thus the distance seems to be longer. it also depends on bc and velocity, lack of time of flight is everything
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rkingston
Optics Apprentice Joined: February/29/2008 Location: Junction, Tx. Status: Offline Points: 97 |
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Another thing you could try is checking your bullet drop with one of the new range finders which has the angle compensator feature built in. You might be surprised by the results.
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Mike McDonald
Optics Journeyman Joined: September/01/2004 Status: Offline Points: 739 |
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Uphill and down hill corrections are the same. YOu are dealing with two different ranges in angle shooting;
ONE is the visual range to target, what you see thru the scope.
TWO is the range to target in which gravity acts on the bullet.
In your 600 yard example the actual range to target is something approximating 415 yards on a flat surface. Gravity acts on the bullet for 415 yards when you take that shot.
In 10-15 degrees and less, there's just about no sight correction.
15-25 degrees is a 10% correction as an approximation
30-45 degrees is about a 20% sight correction.
The numbers are approximate and if we could do graphs on here it would make more sense.
Mike
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8shots
Optics Jedi Knight Lord Of The Flies Joined: March/14/2007 Location: South Africa Status: Offline Points: 6253 |
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This is a rather complex answer. In the end is has to do with the time that gravity effects the bullet at a 90 deg angle to earth.
Should you fire an air rifle and a 300 Win Mag with both barrels level(90 deg to the earth) and both barrels are exactly the same distance from the earth, and should both projectiles leave the barrel at the same moment, both projectiles will strike the ground at the same time. Now let us say it took the projectiles took 1 sec to reach the ground, the air rifle travelling at 500ft per second will be 500 ft from the starting point, and the 300WinMag at 2900ft per second will be at 2900ft from the starting point. Both will reach the ground and their destination at the exact same time. Remember the old experiment of dropping a 10lb and a 1lb weight from a building. They both hit the ground at the same time.
Now, when you shoot at an angle, the gravity is not 90 deg to the level. So the effect of gravity is less. Should you say shoot at a 45 deg incline or decline, then the bullet only spends half its normal time with gravity at 90 deg to level. So the bullet drops slower and appears to go further. So the coorect way is to calculate your horizontal distance, and that is the amount of time your bullet will spend at a 90 deg pull. Should the angular distance be 600yds, but the horizontal distance only 300yds, then bullet drop should be calculated for 300yds.
I have simplified the matter. The mathematical formulae is best left to Einstein.
Mostly on ranges of up to 250yds and a 30 Deg slope, actual bullet rise (or lack of drop) is minimal and can be ignored. Try it on a field target and see for yourself.
The upshoot of this is that heavier bullets do not drop faster then lighter bullets. Slower bullets drop more then faster bullets, due to spending more time at 90 deg to the pull of gravity.
Eureka!!!!!Newton cried when the apple fell on his head!!!
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Dale Clifford
Optics Jedi Knight Joined: July/04/2004 Location: United States Status: Offline Points: 5087 |
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wallis was newtons tutor that actually did the formulas-anyway the formulas 8 shot is referring to use the cosine of the inclination, projectile velocity and trig. -- another way is to use the differential equations for projectile flight and take the derivatives at any time period for the drop along the x axis. the later is easier when done numerically as a difference equation.
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supertool73
Optics God Superstool Joined: January/03/2008 Status: Offline Points: 11814 |
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Thanks guys, this is exactly what I was looking for. I just could not get my head around it with the explanations I got from other students ( to many of them were way off and I got lost) since the instructors did not spend much time explaining it to us. They just taught us the math on how to figure it, but not the reasoning behind it.
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Lifetime warranty and excellent customer service don't mean a thing when your gun fails during a zombie attack.
"A Liberal is a person who will give away everything they don't own." |
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8shots
Optics Jedi Knight Lord Of The Flies Joined: March/14/2007 Location: South Africa Status: Offline Points: 6253 |
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You actually do the maths???!!!
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supertool73
Optics God Superstool Joined: January/03/2008 Status: Offline Points: 11814 |
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No, they taught us the math. I use my mildot master Much easier, I love that thing.
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Lifetime warranty and excellent customer service don't mean a thing when your gun fails during a zombie attack.
"A Liberal is a person who will give away everything they don't own." |
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supertool73
Optics God Superstool Joined: January/03/2008 Status: Offline Points: 11814 |
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It was pretty cool to see it work. After they taught us the math we
went out to a place that had about a 20degree incline and they had
these little tiny bottles full of explosives so when you shot them they
would explode. They were so small and so far away that if you did not
figure it right and get the right dope you would miss. They were 340
yards line of sight, most people was not able to hit them at first. I shot 6 or
the 10 before everyone else got on, it was pretty fun.
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Lifetime warranty and excellent customer service don't mean a thing when your gun fails during a zombie attack.
"A Liberal is a person who will give away everything they don't own." |
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8shots
Optics Jedi Knight Lord Of The Flies Joined: March/14/2007 Location: South Africa Status: Offline Points: 6253 |
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Sounds great. What training are you busy with?
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supertool73
Optics God Superstool Joined: January/03/2008 Status: Offline Points: 11814 |
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I took two different Precision rifle class in March and April. Pretty fun stuff. The head instructor was a Marine sniper for 9 years and served 14 tours in the middle east. Man he was knowledgeable and was a fantastic teacher. One of the other guys was a master tracker so the two of them together was able to teach us a ton about movement and field craft. Most of the field craft was just examples and talking since Front Sight is a defensive school and all. But it was still great stuff to learn about.
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Lifetime warranty and excellent customer service don't mean a thing when your gun fails during a zombie attack.
"A Liberal is a person who will give away everything they don't own." |
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Dale Clifford
Optics Jedi Knight Joined: July/04/2004 Location: United States Status: Offline Points: 5087 |
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tannerite??
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supertool73
Optics God Superstool Joined: January/03/2008 Status: Offline Points: 11814 |
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Yup,t hats the stuff, I could not remember the name
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Lifetime warranty and excellent customer service don't mean a thing when your gun fails during a zombie attack.
"A Liberal is a person who will give away everything they don't own." |
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RifleDude
MODERATOR EVIL OPPRESSOR Joined: October/13/2006 Location: Texas Status: Offline Points: 16337 |
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Mike's description of what's happening is correct. Imagine a right triangle laying on it's side, and the angle you're shooting is the hypotenuse. It doesn't matter whether you're shooting up or downhill. The only thing that matters is the linear distance to the target parallel to the horizon, because gravity has the same effect on bullet drop as if you were indeed shooting horizontally. If you know the angle you're shooting relative to the horizon and your distance to the target along the angle, your actual corrected distance to the target is:
b= c X cos A
where b = actual distance to target;
c = distance to target along shooting angle (hypotenuse of the triangle);
A = angle of the shot relative to the horizon, either up or down.
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Ted
Money can't buy happiness... but it's much more comfortable to cry in a Porsche than on a bicycle. |
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8shots
Optics Jedi Knight Lord Of The Flies Joined: March/14/2007 Location: South Africa Status: Offline Points: 6253 |
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It is a little more complicated then calculating the horizontal distance. It has to do with the amount of time the bullet spends on the 90 deg pull of gravity. Remember, a bullet travels in an arc, not a straight line.
The formula actually looks like this:
where y0 is the initial height, in this case 4 feet; vy0 is the initial velocity in the y (vertical) direction, in this case 0 since all the initial velocity was horizontal; and ay is the acceleration in the y direction, in this case the only acceleration is gravity at -32 f/s2; and t is the point in time where we want to know the position, in this case 0.5 sec. |
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Mike McDonald
Optics Journeyman Joined: September/01/2004 Status: Offline Points: 739 |
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note to self:
Never ask these people what time it is.
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Dogger
Optics Jedi Master Joined: January/02/2007 Location: Ontario, Canada Status: Offline Points: 8916 |
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Guess it depends Mike if you're looking for Metric Vs Imperial time
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God save the Empire!
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