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dummyracer36 · Senior Member

just a theoretical question here... (too many beers and free time last night)

does the angle at which you are aiming affect trajectory? for instance, you are on top of an 8 foot platform, with 3 targets all at 30 yards, but at dif heights, #1 is on the ground, #2 is level with you (8 feet off the ground) and #3 is 8 feet above you (16 feet off the ground)
does the angle affect where the pellet will hit? more to the point, does it affect how the pellet leaves the barrel and flies?

this question arose due to where i shoot, off my back deck into a yard that slopes away from me.

anyone have an answer or a theory?

Dummy

broommaster2000 · Moderator

These things make my head hurt.

Rogerflat · Silver Status Member

If the train is leaving the station heading west at 80 mph...

When you drink you actually sit and think about trajectories????

The answer to your question though is an obvious yes. Trajectory is all about angles. In addition, gravity effects the trajectory throughout the flight path of the bullet.

But think about this, if you shoot straight up, or straight down, gravity has no effect on the point of impact (i.e. trajectory) of the pellet. However, it will effect the speed of the pellet.

dummyracer36 · Senior Member

LOL yes roger... youd be surprised what goes thru my mind when i have a beer in my hand!! its when i have the tools in the other hand friends and family start to worry!!

ok, so its a definite yes that the angle of aim affects flight path, is this something that is a constant? and can it be quantified?

Rogerflat · Silver Status Member

23ib0d0n · Moderator

Check this:
http://www.arld1.com/trajectory.html
from here:
http://www.arld1.com/
Cool

dummyracer36 · Senior Member

wow!! great links!!! answered this question and several other bouncing around in my head!!! thanks a ton!

Rogerflat · Silver Status Member

Yeah, logon to that site, crack open your brews, and have at it!

Juster · New Member

If you are shooting a target uphill at 45 degrees 100 yards away, how do you set your sights?
The easy way is The Rifleman's Method. If the range is 100 yards, 45 degrees uphill, flatten the hill in your imagination. The target will now be closer to you, 70 yards. That's the range you set your sights to. Uphill or downhill is the same (near enough).

The math is: Cosine of 45 degrees = -0.7. Multiply the 100 yard slope distance by 0.7, you get 70 yards . You don't actually do the math, just estimate what the horizontal distance would be.

US Army Field Manual FM 3-05.222 "Special Forces Sniper Training and Employment"
Table 3-9. "Compensation Factors Used When Firing From a Given Angle"
"Percent of Slope Angle Up or Down (Degrees)" = 45
"Multiply Range by" = 0.7

So it's good enough for US Special Forces snipers. It isn't 100% accurate, but it's better than ignoring the slope.
I call this the "Cosine Height" method. The "Cosine Drop" method is more accurate, and multiplies the bullet drop by the cosine of the angle, but you can't do that in your head, unless you are really strange.
More accurate methods would involve an instrument to measure angles, and ballistic tables. You can buy a device like a spirit level which attaches to the rifle, and gives you the cosine of the angle.

kanyon · Silver Status Member

Now my head hurts...So if shooting up hill aim low/down hill high???
Thats about all the info my brain can process.

Rogerflat · Silver Status Member

This will really confuse you then....

Think about it this way. Your scope sits on top of your rifle, right? All things being equal, if the rifle shoots perfectly flat and straight at 30 yards, and if the scope is focused perfectly straight ahead then the point of impact of your pellet will be where? It will be about 3 inches low. Why? Well, that's simple: The scope sits about three inches above the muzzle!

That being said, most people have to adjust their scopes downward to compensate for this. Now, if only it were that simple. However, you have to account for gravity. Gravity makes the POI drop even lower. So in our example, maybe you would have to adjust the scope 4 inches down to also account for the extra 1 inch drop as it travles the 30 yard distance to the target. But if the pellet wasn't effected by gravity and you had adjusted it already, then your point of impact would be 1 inch high.

So what if you aim 30 yards out but instead of shooting something on the ground you aim straight upwards into a tree? If you aim straight up then the trajectory of the pellet will not be effected by gravity. A normal trajectory is a parabolic arc, whereas a shot straight up will just look like a line--straight up and straight back down. Gravity WILL slow the pellet, but it will not effect its trajectory in this scenario.

Now this is the important part. Following the example, if you shoot straight up at 30 yards your point of impact will be, as said before, 1 inch high. So you would aim 1 inch LOW to counteract that.

So, bottom line, if you shoot upwards, aim low.

kanyon · Silver Status Member

Thought that was what I said just a bit more frugal with the words. Laughing

Anyways thanks Smile

billandbeaufort · Senior Member

This is a common subject in the Field Target Matches where they shoot targets as small as 1/3rd of an inch at distances out to 50 yards and up hill and down. The answer is somewhat illogical at first and very complicated mathamaticaly. HOWEVER we don't care about math accuracy we care about point of aim, and luckily for us the solution is very simple! Shoot (AIM) the horizontal distance! YEAH THAT'S ALL! Doesn't matter if it's uphill or down, it's the horizontal distance to target that the pellet cares about. EXAMPLE There is a squirell knockdown target high in a tree, the tree is 30 yards from the fireing line and the target is 10 yards up the tree. The distance from muzzle to target is something like 34 yards because of the angle. To hit that little hole in the knockdown that is only twice as big in diameter as our pellet we must shoot as though the target was at 30 yards (the horizontal distance) Lucky for us this also works when aiming down! So if you are in the tree and the squirell is on the ground, just sight for the horizontal distance. You can go to ballistic web sites but it is so hard to get through the math and it all comes down to HORIZONTAL DISTANCE!

dummyracer36 · Senior Member

thanks alot guys!!! totally answered my query!!! the more i get into this sport, the more fascinated i become!!

yourdaddyjoe · Supporting Member

Here is another for you Racer...

Don't forget to keep your gun level... we have had lots of discusions on this one too...

BTW... I did not have the camera level when I took this photo... He He... Embarassed