Shooting uphill or downhill

[El Chivo]

what type of adjustments are necessary for shooting uphill or downhill as opposed to flat?

intuition tells me to compensate higher for uphill and lower for downhill (because of lessor and greater velocity, respectively) but what are your experiences?

[Ben_Rumson]

Aim lower on both accounts .... The target is closer despite what the bullet path is... Imagine standing at the bottom of a cliff 300 yards high and taking a shot at something near the top...But the face of the cliff is 50 feet in front of you..The hold would be for a shot at 50 feet..Same thing more or less if you're on top of the cliff... Edit: I don't remember the explanation of how gravity comes into play..

[alnitak]

Aim lower on both accounts .... The target is closer despite what the bullet path is...

Yep...

http://www.loadammo.com/Topics/April04.htm

[Gun Smith]

If you drop a bullet to the ground at the muzzle at the same time as the fired bullet leaves the barrel, (barrel level with the ground) they will both hit the ground at the same instant.

[TomD]

Only if the barrel is totally coplanar with the gravitational field. For instance if you shoot straight up bullet will not land same time as one dropped from muzzle height.

Downhill and uphill shots are basically the same deal, hold for horizontal distance.

[AJMD429]

from http://www.loadammo.com/Topics/April04.htm

1. The true vertical bullet drop is the same for level fire and uphill or downhill shooting for the same range. See Figure 1.
2. The vertical drop, do, is the same for all three methods of shooting over the same range.
3. The bullet velocity is the same whether shooting over a level range or shooting uphill or downhill. In other words the bullet does not slow down faster in uphill shooting than with level shooting and the bullet velocity does not increase when shooting downhill.
4. A rifle zeroed in at level range will shoot higher when shooting uphill or downhill. For a given angle of fire the bullet will shoot high by the same amount weather shooting uphill or down hill.

1 & 2 make sense to me, assuming that the 'range' is measured from the muzzle to the target (in other words shooting a target 300 ft in front of you at the bottom of a cliff is NOT the same range as the target on top of that 400 ft tall cliff - it would actually be at a range of 500 ft); the bullet should take almost (see below) exactly the same time to get there, and thus fall the same amount. This also assumes you are judging how 'high' or 'low' to aim based on vertical distance (not the distance parallel to your vertical crosshair, which is tilted towards you).

3 I agree with in general, but if you were shooting straight up [yikes! ], the bullet would truly slow down faster, and take longer to reach the target, than if shooting horizontally (and eventually attain a negative and increasingly negative velocity - lookout ), and if shooting straight down, it would actually accelerate, albeit during the initial time of flight air friction would still slow it faster than gravity would accellerate it (it would still get to the target slightly sooner than the others). The 32 fps/sec would be minimal and insignificant during the typical less-than-a-second time of flight, but there would be a difference, to be honest. I think that difference would also impact to a lesser degree the intermediate angles of fire (vectors and all that physics stuff?). Insignificant perhaps, but aren't we sort of talking theory anyway?

4 I agree with the uphill/downhill being equal (aside from the nitpicking above), but it STILL boils down as to how you define "shooting high" - if you look at the diagram on the website it is showing the 'error' in impact vs. line of sight defined as if you are measuring it perpindicular to the angle of elevation the target it at. That's NOT likely what you'll be doing, because the deer or target or whatever will be standing upright and not leaning towards you at a 30 degree angle!

So... wouldn't it be true that if you go by aiming reticles or milspec nits on your crosshairs* then you should aim 'low' since your estimation of aim will be flawed as you're at an angle. On the other hand, if you go by hoof-to-shoulder distances or lines on a vertically placed target, the drop should in fact be the same, and your aim not need any 'adjustment.'

*(Kwell will usually take care of crosshair nits )

[bj94]

I've read over and over that your gun will shoot high in either case. I've never had a way to verify this.

OTOH I've shot outside archery extensively and it is very easy to prove with a bow that shooting uphill you will shoot LOW but shooting downhill you will shoot HIGH. My guess is that gravity makes a lot more difference for the arrow than it does for the bullet.

[Dastook]

Aim lower on both accounts .... The target is closer despite what the bullet path is...

Yep...

http://www.loadammo.com/Topics/April04.htm

Wow, what a great explanation. I can't tell you how many arguments I have had in the past on this with friends. I will now have some explanation to back up my arguments. You guys on this forum again amaze me with your knowledge.

[Dastook]

Only if the barrel is totally coplanar with the gravitational field. For instance if you shoot straight up bullet will not land same time as one dropped from muzzle height.

+1

If the bullets were fired in a true vacuum of space with gravity as a constant, the bullet would return to the same spot in the barrel it was fired from at exactly the same velocity it was fired.