A Dumb Question About Trajectory

[Industrial Toys]

This question relates to a .177 cal pellet gun but I think it applies to any rifle.

You usually aim a rifle in, for a fairly horizonal shot. How should one compensate if shooting either at a steep angle up or down?

And just curious, but how flat is the trajectory of a department store quality pellet rifle?

Thanks

 

[davesl708]

When shooting up or down will cause the projectile to shoot higher. How much depends on the angle. The steeper the angle the higher the shot until you reach 45 deg. That will be the max effect on bullet rise.

The drop rate of the pellet depends on the speed of the pellet. Drop is a function of velocity, gravity and drag. The faster the pellet the less time gravity has to pull it down. Drag slows the bullet giving gravity more time.

There are calculators available on line to estimate the trajectory.

 

[bcp]

The bullet is affected by gravity over the horizontal distance it travels. So, when you shoot at a target 100 yards away, at say a 45 degree angle up or down, the bullet will strike above the point of aim, as it only went maybe 70 yards horizontally.

Bruce

 

[Industrial Toys]

Thanks. I thought maybe I understood, but the more I think about it and try and figure in the little I know about physics, the less I understand how going both ways could have the same effect.

 

[the old grind]

Good answers. :thumbsup: Recent hand-held rangefinders have inclinometers with which they calculate the horizontal distance when pointed. From that number one can 'hold over' IF they understand their arm's trajectory for the calculated distance.

Ballistic calculators can plot trajectories, given the right data regarding initial velocity and a projectile's 'ballistic coefficient'. With pellets, one only has to shoot at different distances to get a feel for 'drop' at each. Atmospheric and environmental conditions will skew the numbers, esp temperature's effect on traditional powders and CO2-powered pellet guns.

For some of us older guys this puts the challenge in shooting 'moderately powered' arms (vs Lazzeroni calibers and ultra magnums). 'Kentucky windage' is another seat of the pants aspect that is best refined by practice on the bench and in the field.

Shooting to crosshair's point of aim at all distances is for video games. Sighting-in at the bench doesn't guarantee the same results when firing from various field positions (prone, sitting, standing unsupported, etc) Trigger time is key to success.

 

[bcp]

Article with little math:

exterior ballistics

Article with much math:

https://en.wikipedia.org/wiki/Rifleman's_rule

Bruce

 

[Industrial Toys]

Great article, thanks, but I still don't understand. It says the increase or decrease in drag by gravity to be minimal. So, why the difference? I need to print the article and read it a few times. In the mean time, at least I know what the effect is.

 

[bcp]

It says the increase or decrease in drag by gravity to be minimal. So, why the difference?

I think they mean the difference in velocity of the uphill bullet and the downhill bullet, at the same distance, due to gravity. The uphill one slows a bit more due to gravity, and the downhill one slows a bit less, but the difference is minimal.

Bruce

 

[/pine]

When shooting up or down will cause the projectile to shoot higher. How much depends on the angle. The steeper the angle the higher the shot until you reach 45 deg. That will be the max effect on bullet rise.

The drop rate of the pellet depends on the speed of the pellet. Drop is a function of velocity, gravity and drag. The faster the pellet the less time gravity has to pull it down. Drag slows the bullet giving gravity more time.

There are calculators available on line to estimate the trajectory.

I was taught in physics that a horizontally projected object (minus aerodynamics, i.e., wings etc.) will fall at the same rate as a duplicate object merely released and not projected...

It been a long time since I was in a physics classroom so maybe the laws have changed?

 

[bcp]

I was taught in physics that a horizontally projected object (minus aerodynamics, i.e., wings etc.) will fall at the same rate as a duplicate object merely released and not projected...

It been a long time since I was in a physics classroom so maybe the laws have changed?

Drop between gun and target depends on speed and drag as that changes the time gravity has to act.

Bruce