Flight of projectiles from a rifle

[leijen]

Hello all
We at work have been discussing the flight of projectiles from a rifle.
So here is the discussion.
Firstly a rifle is fired at 500m to a target on a horizontal range.
After some adjustment the centre is hit consistently.
Termed a bulls eye.

Then
The target is placed on a hill top above the shooter.
The distance from the target to the shooter is still 500m.
Will the shooter aim at the centre, above the centre or below the centre to achieve a bulls eye.

Then
The shooter is shooting downhill to a target placed at 500m distance.
Will the shooter aim at the centre, above the centre or below the centre to achieve a bulls eye.

Note the distance quoted is from muzzle tip to target in a straight line.

Thanks

Sam

 

[lzkelley]

Above the target in all cases... why would adjusting the aim for the first case change anything in the next 2?

 

[Lojzek]

Yes, the bullet will fly over the target in uphill and downhill case, because the perpendicular component of the force of gravity is smaller than in case of horizontal shooting (I have once tried uphill shoting with a crossbow and the arrow did fly too high).
But I don't think this is true for any distance: if the (uphill) distance is large enough that the speed of the bullet in the direction towards the target is significantly reduced (by the parallel component of the force of gravity), then the bullet might hit too low.

 

[berkeman]

Google is our friend. I googled shooting uphill and downhill, and here's one of the first hits. From Guns and Ammo magazine, so you konow it's right!

http://www.gunsandammomag.com/gun_columns/notes/gn0409/index.html


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[leijen]

Ballistics

Thanks to all that placed a reply.

This will silence all the critics and those who genuinely want the correct answer.

Sam

 

[Lojzek]

I noticed I didn't read the question carefully: I assumed that the shooter aimes the center of the target through a sight mechanism that compensates the free fall of the bullet so that a perfect hit is achieved in case of horizontal shooting at the given distance (then the bullet will fly over the target for uphill/downhill shooting).
But now I noticed that the question was the mental adjustment that is required to hit the (uphill/downhill) target. In this case the shooter should aim below the target in both cases (if the sighting mechanism for horizontal shooting is used).