Home Forums Hunting & Shooting Ask The Gunwriters .270 trajectory from treestand?

Actually, gravity is a constant that doesn't recognize horizontal distance, either. It recognizes and acts on time. That's why a bullet dropped from the hand and a bullet fired horizontally will both hit the ground at nearly the same time (there is a slight vertical componet to drift, so the fired bullet will hit very slightly later).
The time of flight over a given distance at angles normally encountered when shooting is very nearly the same, therefore the effect of gravity is also very nearly the same.

It takes distance as a factor because its rate of pull is contant, so the distance it pulls the object depends on how high it is, and therefore at what speed it falls.

Horizonal distance is a factor in ballistics, although not much else. I know of course it's the exposure time and the velocity, but another way of descibing that could be horizontal distance, since essentially that's what it is...well, it's not horizontal, a bullet flight is a parabola.

Point being, it is definitely not a fucntion of trigonometry. Trig only works with straight lines, and a bullet doesn't fly in a straight line. Therefore if you depend on Trig to determine "true" distance to a target, you may or may not be using the right leg of the triangle.

you fellas crack me up ... do you realize how high you'd have to be up a tree for it to even start to think about making any practical difference???

<img src="/ubbthreads/images/graemlins/laugh.gif" alt="" /> <img src="/ubbthreads/images/graemlins/laugh.gif" alt="" /> <img src="/ubbthreads/images/graemlins/laugh.gif" alt="" />, me too, you guys are arguing how to say the same thing...........DJ

In a vacuum.

No, in real life. It crosses the line of sight in two places. That, I believe, is a a parabola. In a hunting rifle, at least. Fired from a rest with no regard to sighting in, it still is a curve, not a straight line.

In a vacuum, with the same gravity as we have, it would still be a parabola. THink about it.

Nope.

Mathman is correct.............DJ

Well, a curve then.

Okay guys, now you have me thinking that I should hold high at that range. That is what I would have done before asking. I have a 4x12x40 Bushnell scope mounted what I would consider not abnormally high. I could site my gun 2.5 inches high no problem to increase my point blank. That would be easy. There are sure alot of differing opinions on this topic!!! But that is what I wanted...guys with hunting experiences similar to this situation as well as guys that have it figured out by the numbers. Chris.

I should say that I once shot a deer with the same gun/scope combo that was no more than10 yards out in front of my old tree stand(same height).I was shooting damn near straight down it felt like.I aimed for my side of the spine just behind the shoulder and the bullet travelled down through the lung, took out the heart and made a huge hole just inside the opposite front leg. The deer went about 75 yards and then did a summersault and lay dead. It was in an open field but if it was in the bush there was a huge blood trail for me to follow. That was sweet!! That could happen too this year but I want to be prepared for the long shot. Chris.

Chris, I like to sight in dead on at 200. That way you just aim dead on at most normal hunting ranges. At 300yds you aim at the spine. If you aim at the spine and it's not quite 300yds you'll end up with a high lung shot. If it's a little more you'll get a heart shot. Some guys prefer the max point blank range theory but I prefer to know exactly where I'm dead on at. The minimal height of you tree won't change the point of impact in any meaningful way, you have to be shooting at a pretty steep angle up or down before it really makes much difference.................DJ

From tree-stand heights, it's not a factor, I would think.

Where it is a BIG factor is for snipers. I'm not a sniper, but I went to the US Army Sniper Instructor school, which is where I learned not to trust my judgement. If you're shooting from tall buildings at distance, it matters a lot.

I suppose if you were in the mountains out west goat hunting, it could matter. If you are, say, 400 feet up a mountain and you see a goat below you, and you range it at 500 feet, the real distance is more like 300 feet, which is the distance that gravity acts on the bullet.

That's the 3-4-5 rule for a right triangle, and if you ever take a GRE or even a SAT, you'll get plenty of chances to use it...or multiples thereof. It's the way we used to square house foundations....measure 30 feet one side, 40 feet the other side, and stretch the tape between the two points and hope it turned out to be 50 feet.

One more time; It isn't the distance that gravity acts on the bullet, it's the time. When shooting at an angle not all of the drop (which is always verticle) acts at a right angle to the line of sight. At 500 ft you would have to be shooting a real slow rifle to miss a man. Archers who have to contend with slow missles with a lot of drop do have to worry about.
Good Luck!

The difference in time isn't much of an issue at the ranges we're talking about, given that gravity pulls at a constant rate of 32 fps/ps. We're not talking seconds here, we're talking in .0001 seconds. There might be 1/10000 of a second difference in exposure time between a bullet travelling 300 feet and one travelling 500 feet. The distance that bullet will drop in that short amount of time is in your calculator.

Do the math on that, and you will see it makes almost no difference at all.

Exposure time really counts in windage calculations at longer ranges.

Not to encourare this thread but wind drift depends on the velocity lost not the time of flight.
Good Luck!

Sorry, but you're entirely wrong. Drift is a function of the ballistic coefficient of the bullet, wind velocity and the exposure time.

Of course, the velocity drops which increases exposure time.

You might want to check with one of the ballistic programs, which figures it out for you.

edited

The best explaination of bullet drift is in "Rifle accuracy facts".
The spin stabilisation turns the bullet so that the "wind' is blowing straight back (zero angle of attact). Part of the drag is now down range and causes the drift. Since ballistic coefficent is defined as velocity lost, drift depends on the velocity lost. No Virginia the wind doesn't blow against the side of the bullet.
Take Care!

Incidently, the correct term is "wind deflection," and it leads me to my favorite ballistics quote from my friend and mentor, William C. Davis, Jr.:
"It is a fact that a .22 Long Rifle bullet fired at a muzzle velocity of 1255 fps will reach a 100-yard target about 0.269 second after firing, and the wind deflection in a 10-mph crosswind will be about 5.2 inches. It is also a fact that a .22 Long Rifle bullet simply dropped from the hand at the instant the gun is fired would fall about 14 inches during the same 0.269 second time of flight, and thus it would be exposed to the wind for the same length of time as the bullet that was fired at the 100-yard target.
"If the wind deflection depended directly upon the time that a bullet is exposed to the wind, then a .22 Long Rifle bullet simply dropped from a height of 14 inches in a 10 -mph crosswind would 'drift' sideways about 5.2 inches during its fall. We probably know intitively that this will not be the case, but if experimental proof is needed, then the simple experience of dropping a .22-caliber bullet from a height of 14 inches in a moderate breeze will be enlightening."

The problem with you analogy is that if you fired a .22 LR bullet with the axis of the bore level with the ground and 14" above the ground, and dropped a bullet at the same time, the bullet you fired would hit the ground about 30 or 40 yards in front of the muzzle.

You can look at a trajectory chart to see how many inches above true level a .22 rifle bullet must be sighted to hit a target at 100 yards. It is from that height, in your analogy, the bullet must be dropped.

Leave out the range of 100 yards, and your mentor is correct.