trajectory angle

[komifornian]

I’m curious how much shooting angle affects a bullet’s flight.

Here’s the scenario so to better frame my question:

1) I’m at sea level
2) The distance to the target is 600 ft
3) Elevation gain is 300 ft
4) Linear distance is 671 ft
5) A 60 grain bullet traveling at 3,700 fps

This is just a model for simplicity. I’m sure that at this distance and the velocity of the projectile there won’t be much of an effect. However, at longer distances there will be.
The question is: At what point does the trajectory angle become something that really needs to be considered?

 

[SSSamurai]

Re: trajectory angle

The simple answer is; when the angle and/or range are enough to make you miss if you don't correct for it. There isn't really a hard and fast rule, that I know of, because it depends. At longer ranges the angle is more important and higher angles the range is more important. I love ACIs for this, you can get a good idea of how much the angle will affect your range at a glance.
Jason

 

[komifornian]

Re: trajectory angle

thanks, you answered my question. I was really wondering if there was a hard rule.

 

[Pat M]

Re: trajectory angle

here ya go:

http://www.snipertools.com/article5.htm

 

[ggmanning]

Re: trajectory angle

Or this if you want a cheaper alternative......you can also use a string, a small weight and the mil dot master also.

http://www.slopedoper.com/purchaseSlopeDoper.html

 

[MikeeBooshay]

Re: trajectory angle

We shoot a lot in similar conditions. A rule of thumb, depending on the degree of accuracy required, is that angles less than 30 degrees, at ranges less than 300 yards, require little to no correction for uphill/downhill shooting.

This is keeping in mind that most of our shooting is at hunting size targets, 3 MOA/1 mil approximately.

Obviously, a near vertical 100 yard shot would fall outside that criteria, your example would not. If concerned about that shot, a favor towards the bottom of the target zone would be a conservative call.

A neat trick a smart guy taught me, was setting a target ( soda can ) at the foot of a canyon, about 600 lasered yards away, approximately 30 degree down angle. Shoot the can, adjusting the scope elevation dope so no hold is required. Set another can right next to you, and go to the target sight down the hill. Half the group wants to change the dope, but don't. Shoot the can, demonstrating that the correction is the same up or down hill.

 

[gstaylorg]

Re: trajectory angle

Try this thread; also has some links to more info on your question.

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=2333157#Post2333157

 

[sniperaviator]

Re: trajectory angle

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: komifornian</div><div class="ubbcode-body">I’m curious how much shooting angle affects a bullet’s flight.

Here’s the scenario so to better frame my question:

1) I’m at sea level
2) The distance to the target is 600 ft
3) Elevation gain is 300 ft
4) Linear distance is 671 ft
5) A 60 grain bullet traveling at 3,700 fps

This is just a model for simplicity. I’m sure that at this distance and the velocity of the projectile there won’t be much of an effect. However, at longer distances there will be.
The question is: At what point does the trajectory angle become something that really needs to be considered?

</div></div>

The way I read your question, the horizontl distance is 600'.
The elevation gain is 300'
So the hypotenuse of this right triangle is 671'.
The angle is the arctangent of 300/600 (.5) which is 26.5 degrees. So you are shooting uphill (or downhill) 26.5 degrees. This is a fairly steep slope. It would be an expert ski run. It would be too steep for a road (except a STEEP jeep road).

You need to use ballistics table for 600', (200 yards) and not the 671' (224 yards). Just use the ballistics (UP moa) for the HORIZONTAL distance. Although you gave that distance in your question, usually you have to calculate it. What you see, straight line, is the hypotenuse distance and actually the horizontal line distance is r * cos(theta), where r is the 671' and theta is the 26.5 degrees. So you have to have a way of measuring the degrees of uphill or downhill. Some sort of instrument for that like a transit or angle measure of some sort.

 

[komifornian]

Re: trajectory angle

I'm shooting up hill. And yes it's steep enough to be considered out of bounds for 90% of the vehicles out there.

 

[sniperaviator]

Re: trajectory angle

You use LESS moa for the steep elevation change. It is the HORIZONTAL distance that your ballistic chart is calibrated for.

 

[komifornian]

Re: trajectory angle

ah okay that makes sense...

 

[Lindy]

Re: trajectory angle

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Just use the ballistics (UP moa) for the HORIZONTAL distance.</div></div>

That won't work on shots at significant angles and distance.

Better is to multiply the dope for the actual distance through the air by the cosine of the angle to the target.

And that was explained in the thread link previously posted, which I recommend reading.

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=2333157#Post2333157

 

[sniperaviator]

Re: trajectory angle

Listen to Lindy. He knows more than I do. (Mine will work in a vacuum, like on the MOON)

 

[JxMAN25]

Re: trajectory angle

i really like the look of anything desert earth, but its up to you man. Jesse