Shooting Up or Down Hill - why aim low?

[Monkey Spanker]

An interesting point on vertical shooting. The nephew of a keeper I used to work under years ago was a sniper in the forces, think it was the Marines. I remember him telling us about going to the Grand Canyon as part of his training to learn vertical shooting. I don't think I understood it then, and still don't, but a bullet fired vertically does not travel in a straight line, it is pulled by the rotational force or something, so they had to allow for it just as you would compensate for gravity.

What you have probably heard about is known as 'projectile drift' and effects spinning ballistic projectiles at longer ranges. I'll try not to get too technical, but a spinning bullet behaves much the same as a gyroscope and suffers from gyroscopic precession. At longer ranges, the curved trajectory creates pressure under the nose of the bullet. This pressure when applied to what is effectively a gyroscope then acts at 90 degrees which pushes the bullet to the right.
The Coriolis effect mentioned does affect small arms but is much dependent upon location and direction fired. It is greatest near the poles and negligible at the equator. For small arms, the coriolis effect is considered as insignificant.
Neither of these effects are significant to concern us at normal stalking ranges though!
MS

 

[NigelM]

What you have probably heard about is known as 'projectile drift' and effects spinning ballistic projectiles at longer ranges. I'll try not to get too technical, but a spinning bullet behaves much the same as a gyroscope and suffers from gyroscopic precession. At longer ranges, the curved trajectory creates pressure under the nose of the bullet. This pressure when applied to what is effectively a gyroscope then acts at 90 degrees which pushes the bullet to the right.
The Coriolis effect mentioned does affect small arms but is much dependent upon location and direction fired. It is greatest near the poles and negligible at the equator. For small arms, the coriolis effect is considered as insignificant.
Neither of these effects are significant to concern us at normal stalking ranges though!
MS

The poor OP just wanted a simple explanation!!!

Are we to refer to you as MS the Tank Commander from now on?

 

[Monkey Spanker]

The poor OP just wanted a simple explanation!!!

Are we to refer to you as MS the Tank Commander from now on?

I did try to keep it simple!
I've always been 'Anti-tank' though!
MS

 

[Cyres]

To simplify the bullet will strike high so you aim low. I have a cosine indicator on my FAC air rifle and its very handy when you a shooting squirrels high up in trees and you do have to aim low, even bigger issue when shooting sub fac air rifle across a steeply sloping bank when you have rifle cant as well, missed many a rabbit because I didn't understand, always thought shooting low so would aim higher and off course that was the wrong solution.

MS is alsso correct in saying you do have to give consideration to the bullet path when you shoot deer at steep angles, not a problem on other quarry if using BT bullet

D

 

[bewsher500]

just get closer! then shoot!

 

[AN DU RU FOX]

simple shoot uphill and walk downhill,

 

[RICK O SHEA]

This might help

 

[davidm]

Easiest way to explain would be set a target up either uphill or downhill aim for centre then go and see where the bullet has struck. No better way to explain than physical evidence.

 

[private fraser]

First find a decent hill in North Norfolk

 

[NewForester]

Because the horizontal distance to the target is less than the line of sight distance (up or down the hill)

+!

And it is upon the horizontal distance that gravity exerts its force.

 

[.243 t3]

Counter-intuitively, this error applies to shooting both uphill and downhill. Whethershooting an up or down slant, you must hold low to hit the target.

 

[dom8328]

Jesus, my eyes are bleeding and my head is spinning after reading all that. At last, a simple answer

 

[Monkey Spanker]

+!

And it is upon the horizontal distance that gravity exerts its force.

If you could accurately determine the horizontal range component to each target and use that to compensate for elevation error it would work, but this is quite simply not possible in most situations. To say that gravity only affects the horizontal plane is just misleading though! Gravity effects are at a maximum when horizontal, but gravity affects the bullet in every plane, even vertical! If it didn't, then other than air resistance, it would be possible to fire a bullet vertically into space!!
MS

 

[Bandit Country]

If it didn't, then other than air resistance, it would be possible to fire a bullet vertically into space!!
MS

Surely it is possible to fire a bullet vertically into space? You'd just need an incredibly big cartridge case and lots of very powerful propellant ...?

 

[Timney]

In really simple terms, because that's what I understand, you only consider the horizontal distance. So it might be 200 yards away, but if you are shooting down at 30 degrees that will only be about 170 yards of horizontal distance so that's what you allow for.

With calibres that shoot +\- 1" to 200 yds or thereabouts at normal stalking distances it's not really something you need to worry about too much. Stretch out to 300 yds and start shooting at 30 degree angles (pretty extreme) and you need to factor it in.

As this fellow says, this is my understanding as well.

 

[Monkey Spanker]

Surely it is possible to fire a bullet vertically into space? You'd just need an incredibly big cartridge case and lots of very powerful propellant ...?

Not really possible. The escape velocity would have to be 11.2 km/s !
Even if you could get a projectile to go that fast, it would disintegrate or burn up with friction through the atmosphere.
Not even a Blaser or a .17 HMR could achieve such a feat!
MS

 

[Bandit Country]

Not really possible. The escape velocity would have to be 11.2 km/s !
Even if you could get a projectile to go that fast, it would disintegrate or burn up with friction through the atmosphere.
Not even a Blaser or a .17 HMR could achieve such a feat!
MS

What about sticking the bullet on the pointy bit of a Saturn 5?

 

[Dorsettaff]

What about sticking the bullet on the pointy bit of a Saturn 5?

Too over-bored....barrel life would be 1-2 minutes...tops

 

[The Singing Stalker]

My air rifle has been tuned up and I regularly launch pellets into space.
Shot an alien once.
sent pictures to the tabloids so it must be true.

 

[AN DU RU FOX]

Surely it is possible to fire a bullet vertically into space? You'd just need an incredibly big cartridge case and lots of very powerful propellant ...?

They have with fins,they do it pretty regular ,lot of trouble for nothing if you ask me,just to get a picture of another lump of rock!!