Downhill shooting

rimfireguy

Hello all. I'm fairly new to this forum, based in Kerry and have following query.
Was shooting rabbits the other evening with new CZ .17 HMR I had picked up and zeroed previous week. (1/2 inch high at 100yds) Very happy knocking rabbits 60-120 yards until I came across a shot from on top of a bank (15 feet approx) to base of a ditch opposite approx 110 yards. I had read somewhere to always stay under target when shooting downhill, did this but bunny kept on chewing and did so for next 2 shots also. Only on 4th attempt did he roll over as I held on top of his back. Admit I'm less than expert rifle shot but wonder what is best way to approach downhill targets. Thanks.

dwighet

rimfireguy wrote: »

Hello all. I'm fairly new to this forum, based in Kerry and have following query.
Was shooting rabbits the other evening with new CZ .17 HMR I had picked up and zeroed previous week. (1/2 inch high at 100yds) Very happy knocking rabbits 60-120 yards until I came across a shot from on top of a bank (15 feet approx) to base of a ditch opposite approx 110 yards. I had read somewhere to always stay under target when shooting downhill, did this but bunny kept on chewing and did so for next 2 shots also. Only on 4th attempt did he roll over as I held on top of his back. Admit I'm less than expert rifle shot but wonder what is best way to approach downhill targets. Thanks.

The angle of the hill has to be quite acute before you need to compensate...

best way to work it out is practice....
Put up some paper targets and have fun...

FISMA

RimFire,
Give this thread a read
http://www.boards.ie/vbulletin/showthread.php?p=67065354

This may help as well
http://www.boards.ie/vbulletin/showthread.php?p=69516659

rimfireguy

Thanks for replies to "Downhill Shooting" query.
Answers definitely make sense, come to think of it, distance was longer when I
paced it out than I first thought when taking the shot.

FISMA

I thought we sussed this one out?

When you are shooting at large angles, as mentioned, you aim low, whether up or down.

"Shooting uphill or downhill causes the bullet to strike higher," which is why we shoot lower.

A nice link. Please advise if I misread.

zlezlius

From what I've read when I started shooting, I have to agree with FISMA: uphill or downhill always aim lower. Couple explanations I just found why:

http://www.firearmssite.com/shoot_uphill.htm

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

FISMA

I learned this the hard way. I stalked a deer under perfect conditions from 600ya to within 100ya. It was downhill and I thought you were supposed to aim high.

All the time in the world. I took my time, breathed perfectly, great trigger pull, and I saw the splash over the deer's back. D'oh.

Deer runs about 50m in an arc so the shot hasn't changed. I remember thinking that's the second mistake the deer has made. I won't make another.

This time the deer is looking at me. I aim for boiler room and catch it in the neck.

Let's go with the triangle above, but for 300ya, 400ya, and 500ya.

Suppose you are at the top of the above hill and the target at the bottom. The target is a distance of 500ya away - line of sight.

If your name was Poulo or Tack (:-) then it would make sense that we would zero our reticle at 500ya on the horizontal.

At the greater distance, we would have taken into account more bullet drop than at 400, 300, or 200 ya.

Thus, if we shot out to 400ya, on the horizontal, with the crosshairs on target, we would shoot high.

Here is where the problem is.

When shooting, it is the horizontal distance that matters and not the angled.

Again, our kit is sighted in horizontally at 500ya and making bullseye's. When we are on a hill, we see the target 500ya away, line of sight. However, horizontally speaking, it is only 400ya away.

If we shoot as if the target is 500 horizontal yards away, we will miss high. That's why we shoot low.

It doesn't matter if we shoot up or down, the angle is still the same.

With all this said, I bet some Marine Corps sniper could differ in some specific instances. However, in general, I think the rule of thumb is to aim high in life and low in shooting.

fodda

To me that is obvious, so explain the same about shooting low to hit same target uphill, that's the bit i do not get

It wasn't me!

fodda wrote: »

To me that is obvious, so explain the same about shooting low to hit same target uphill, that's the bit i do not get

The only thing that acts on a bullet in terms of trajectory is gravity. This only acts vertically, so if you range a target which is 150 yards from you in a straight line, but uphill, the lateral distance across which gravity is acting is less than 150 yards, the extent determined by the angle of the slope, so the trajectory is determined by gravity to a lesser extent than if it were 150 yards on flat ground. I would like to point out that "aim low" should not be taken absolutely literally. The drop will be less than the same line of sight distance across flat ground, but for typical cartridges at typical hunting ranges, you'd have to be at a massive angle for it to make a difference. Out at 300+ yards, you'd have to account for more moderate slopes, but as with most things, it's not as important as it might seem.

fodda

So to keep it in round figures we say on the flat we range our rifle to hit bullseye at 1000yards or whatever, then one day from the same position to the target is uphill at an angle of 45 degrees and the distance is exactly the same 1000yards or?....... So now i shoot below it to hit the bullseye? when everything is exactly the same except we are now shooting uphill at 45degrees?

It wasn't me!

fodda wrote: »

So to keep it in round figures we say on the flat we range our rifle to hit bullseye at 1000yards or whatever, then one day from the same position to the target is uphill at an angle of 45 degrees and the distance is exactly the same 1000yards or?....... So now i shoot below it to hit the bullseye? when everything is exactly the same except we are now shooting uphill at 45degrees?

Yes, because if the line of sight to the target is 1000 yards at an angle, then the distance in terms of the horizontal is considerably less, and that's the distance acted upon by gravity.

fodda

No nothings changed except the earth just got slanted at 45 degrees, me and the target are still in the same position exactly 1000 yards from each other on a measuring tape.....so i shoot low?

It wasn't me!

fodda wrote: »

No nothings changed except the earth just got slanted at 45 degrees, me and the target are still in the same position exactly 1000 yards from each other on a measuring tape.....so i shoot low?

In line of sight terms, yes, you are the same distance apart. However, the distance across which gravity is acting is lessened, as this does not follow line of sight, but is vertical. Using the triangle in FISMA's post above, if you're looking along the distance 5 (1000 yards), then on flat ground, obviously, that's 5, because gravity is effective across 1000 yards. However, at an uphill angle, as in that picture, gravity is only effective across distance 4, so your trajectory will be exactly the same as if you were only shooting across distance 4 on flat ground, because you effectively are, even though your line of sight is 5.

FISMA

fodda wrote: »

To me that is obvious, so explain the same about shooting low to hit same target uphill, that's the bit i do not get

Fodda, I agree, which is why I learned this the hard way.

I am going to have to think about this one and come up with a nice presentation on powerpoint or youTube. People still question this one a lot, seems worth the effort. Also, I still haven't thought it out 100%.

Reticles are scaled with the horizontal in mind. Thus, it is not surprising that for an angled shot the horizontal distance is taken into account.

Perhaps, someone could make a digital reticle that could change its scale based upon angle of gun.:rolleyes:

Anyhow, if we forget about air resistance for a while, the only Force acting on the bullet is gravity. Gravity pulls straight down, whether up or downhill.

Indeed, even with air (let's say still air), why would the Force of air resistance change the flight of the bullet when going up or down?

It wasn't me! wrote: »

I would like to point out that "aim low" should not be taken absolutely literally. The drop will be less than the same line of sight distance across flat ground, but for typical cartridges at typical hunting ranges, you'd have to be at a massive angle for it to make a difference. Out at 300+ yards, you'd have to account for more moderate slopes, but as with most things, it's not as important as it might seem.

+1 - agreed.

A 100ya shot would have to be at a ridiculous angle to physical have to aim low.

fodda

On Fismas triangle 5 which is a "diagonal" will by its mathematical nature be longer than 4 or 3 so how is 5 shorter than 4.....5 is longer than 4 and it is up hill?

If we measure 4 and its exactly 1000yards on a tape measure and then we lift the target (where 4 meets 3) up in the air keeping the tape measure tight so the measurements are still exactly the same and its at any angle you want .....we then shoot low?

Sorry i am totally confused by this, perhaps Fismas triangle is a bad example

It wasn't me!

No, you got it. If you have a line of sight distance of 5 on flat ground, and then raise it to make the angle in FISMA's illustration, you aim as you would if the distance were 4, because 4 is now the distance across which gravity acts and therefore determines the trajectory. the distance in terms of line of sight is still 5, but the trajectory mirrors the distance across flat ground, which is 4.

dev110

FISMA wrote: »

I learned this the hard way. I stalked a deer under perfect conditions from 600ya to within 100ya. It was downhill and I thought you were supposed to aim high.

All the time in the world. I took my time, breathed perfectly, great trigger pull, and I saw the splash over the deer's back. D'oh.

Deer runs about 50m in an arc so the shot hasn't changed. I remember thinking that's the second mistake the deer has made. I won't make another.

This time the deer is looking at me. I aim for boiler room and catch it in the neck.

Let's go with the triangle above, but for 300ya, 400ya, and 500ya.

Suppose you are at the top of the above hill and the target at the bottom. The target is a distance of 500ya away - line of sight.

If your name was Poulo or Tack (:-) then it would make sense that we would zero our reticle at 500ya on the horizontal.

At the greater distance, we would have taken into account more bullet drop than at 400, 300, or 200 ya.

Thus, if we shot out to 400ya, on the horizontal, with the crosshairs on target, we would shoot high.

Here is where the problem is.

When shooting, it is the horizontal distance that matters and not the angled.

Again, our kit is sighted in horizontally at 500ya and making bullseye's. When we are on a hill, we see the target 500ya away, line of sight. However, horizontally speaking, it is only 400ya away.

If we shoot as if the target is 500 horizontal yards away, we will miss high. That's why we shoot low.

It doesn't matter if we shoot up or down, the angle is still the same.

With all this said, I bet some Marine Corps sniper could differ in some specific instances. However, in general, I think the rule of thumb is to aim high in life and low in shooting.

It is amazing how I post a reply like this on another thread and it got deleted!!

fodda

It wasn't me! wrote: »

No, you got it. If you have a line of sight distance of 5 on flat ground, and then raise it to make the angle in FISMA's illustration, you aim as you would if the distance were 4, because 4 is now the distance across which gravity acts and therefore determines the trajectory. the distance in terms of line of sight is still 5, but the trajectory mirrors the distance across flat ground, which is 4.

:eek::eek: Yeah right whatever you say. I dont want to think about it anymore i need a drink.

It wasn't me!

fodda wrote: »

:eek::eek: Yeah right whatever you say. I dont want to think about it anymore i need a drink.

I have a beer here. It does help. Like I say, it won't typically make any difference for most hunting situations, but for some hill stalking where shots can be longer and angles steep enough, you'd want an idea of the theory and some practice at it.

fodda

It wasn't me! wrote: »

I have a beer here. It does help. Like I say, it won't typically make any difference for most hunting situations, but for some hill stalking where shots can be longer and angles steep enough, you'd want an idea of the theory and some practice at it.

Thanks for trying to explain it but i just cant get it, never was any good at that type of maths stuff. If i ever take up deer shooting and they are up a hill.........they can f....g stay there:)

It wasn't me!

Do you have a centrefire rifle and a decent drop chart? If so, do an experiment. Use a single aiming mark, preferably something like a Shoot'n'See target and stick it out at about 350 to 400 yards so you have a decent range to emphasise the difference. Use your settings for that distance and fire a group on the target on flat ground. It should be centred. Then find a spot to fire a group at the same distance by the rangefinder, but up or downhill at a steep angle, at least 20 degrees, and preferably more. Use exactly the same scope settings and point of aim. The group will be higher on the target. Guaranteed. This will be because while your line of sight is the same, the trajectory is for a shorter distance as that is what gravity acts on. Actually, consider the following example:

You're on the edge of a cliff, facing another sheer cliff. It's exactly 200 yards away in a straight line. Let's say it's 400 yards again. You put a target exactly opposite you, zero and fire a group, centred. Now, shoot at another target fifty feet higher on the cliff opposite you. In line of sight terms, it's further away (for argument's sake let's say it's 450 yards in line of sight), but if you were to aim high to account for the difference(or click up to your 450 yard settings), you'd hit high. If you aim dead on, it'll hit dead on, because gravity only acts vertically, so imagine gravity as a vacuum in the gap between the two cliffs, and gravity is the only thing affecting your bullet's trajectory materially. Therefore, the distance across which the trajectory is determined is still 400 yards, even though the target is further away in a straight line. Try it and see.