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Aight, you guys call this slope dope right? When your target is above or below you because of a hill or other elivation situations. This affects terminal ballisitcs and also the trajectory of the bullet right? Im obviously shooting paper targets with my powerline 880 pellet rifle for now btw. ;) I know you guys don't like air rifle discussion, but the problem is related to real rifles too. So please forgive me.

Anyway, I read that hills decieve range estimation? It's truely more shorter of a distance compared to a flat area?

Now what about my trajectory? WHat can I do to fix this? And tell my angle
 

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jc71corvette said:
I know you guys don't like air rifle discussion, but the problem is related to real rifles too. So please forgive me.
I think this question is very pertinent to anyone who does unknown distance shooting, and I am interested in the answer, too.

Scatch Maroo
 

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jc71corvette said:
Im obviously shooting paper targets with my powerline 880 pellet rifle for now btw. ;) I know you guys don't like air rifle discussion, but the problem is related to real rifles too. So please forgive me.
Why would some one not like an air rifle question on here? I understand this is a "Sniper" website and forum, but whats the big deal? Kinda hard for your average guy to pull of a few rounds in the backyard now days. :p Pellet rifles are good for "practicing" or having fun if your stuck in a place where you cant use real rifles.

The Rifleman
 

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re

As far as I gather, it does not matter if the target is above or below you, all that matters is the straight line distance as the Eagle flies.

If someone is 50m's away, gravity will effect the bullet for 50m's, while if he is 50m's away and 10m's up, gravity will still only effect 50m's worth.

That said, a target 50m's away, and 50m's up, would mean the bullet has a diagonal parth to follow and so greater distance to cover, so would be effected by gravity for longer.... so I don't know. :?

Oh, and I am one of the few people here who also appreciate air rifles. :wink:
 

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Yeah, I remember that talk.

If your target is higher than you, you will overshoot.

If your target is lower than you, you will still overshoot.
 

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um just for a general rule of thumb, if you are shooting paralel to the ground it doesnt matter too much...

physics speak -

when determining your trajectory of a straight path, you have two coordinates an X and a Y, X being horizontal trajectory and Y being verticle trajectory. say you shoot something 20 m/s and earth has ~ 10 m/s gravity, thus every second you will go 20 meters out and 10 meters down - discluding air friction since most trajectory bullets have near negligable air friction.

now thats on a straight plane

now on a diagnal, its semi tricky, but not impossible at all - now if you want to work this out, get a sheet of paper, otherwise itll be tricky to explain.

now draw an X-Y plane (graph with just the axis), now normaly on a straight plane, you will be shooting and the bullet is going whatever way on the X axis, and down on the Y axis - but - since your angled, say 45 degrees just to make it easy, you now have gravity, still going on the Y axis, but now your bullet is going -45degrees, so now you have to put your line not on the X axis, but with a negative slope in the (-x, -y) sector of the graph(this is the same look as this equation - y=1x+0)

now that your graph is made, lets keep the 20 m/s bullet and 10 m/s gravity, label your line that is on the Y axis with 10 m/s, and your diaganal with 20 m/s - now since you want the verticle speed and not the diagonal speed, you need to "rotate the graph 45 degrees", and in order to find your new numbers, use your good ole, triganometry using the Sin function ( Sin*theta(angle) = opposite/hypotenuse ) we know what the HYP is, 10, and we know the theta(angle) so take Sin*45 = opposite/10 - thus simplifing down to .71 = OPP/10, then OPP = 7.1

so now you know your bullet is dropping at 7.1m/s and your gravity is pulling at 10m/s, making 17 m/s drop

p.s. if i fuckered something up tell me, im sleep deprived, worn out, hungry, and i havent done physics in a while lol
 

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American Rifleman said:
jc71corvette said:
Im obviously shooting paper targets with my powerline 880 pellet rifle for now btw. ;) I know you guys don't like air rifle discussion, but the problem is related to real rifles too. So please forgive me.
Why would some one not like an air rifle question on here? I understand this is a "Sniper" website and forum, but whats the big deal? Kinda hard for your average guy to pull of a few rounds in the backyard now days. :p Pellet rifles are good for "practicing" or having fun if your stuck in a place where you cant use real rifles.

The Rifleman
Yeah,i know,the only thing i can use around here are pellet guns.I was really supprised when i went through a real small town about a week back and saw someone who had a whole pistol range on his front yard,pepper poppers,paper targets,benches and all that right next to the main road.He also had a police cruiser,which may have had something to do with it.
 

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Humm...
ah yes the math of shooting and all the numbers to blow your mind.
:shock:

The accepted constant of gravity is not 10 meters per sec but 9.81m/s
Guys keep checking the website there is going to be a posted article in the members only area on angle shooting soon.
Cheers,
Kenshin
 

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Let me put it simpler. Pothagrin therum (sp) a squared+b squared=c squared.
 

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Recoil said:
All of that math is hunky-dory, except it has nearly nada to do with the problem. There was no talk of acceleration, escape velocity, decceleration, etc., other than the gravitational constant, which as was pointed out, is -9.81 at sea level. Shikaku treated the problem as a linear, two dimensional one, and alas, the problem is more complicated than that. If Shikaku's math equated directly to ballistics, your bullet would hit the dirt within a couple of seconds.

I'm not trying to be an ass and put anyone down...The math was okay, but it's just not that easy. There's a reason entire books have been written on this subject, and why snipers and serious marksmen spend so much time studying it...Not surprisingly, it's the same reason most people never truly master it. :wink:

I spent some time in college doing some ballistics studies and you'd be damn surprised to learn how hairy the math can get! If you want to get serious, break out the calculus. :shock:
Actuallyit is as simple as the pothegram therum (sp) Your zero should be the distance of the base of the triangle, not the sloping edge (cant remember technical term?

So lets say you are shooting down hill at 45 deg slope. The distance is say 500 yards. (i'm making the numbers up so they will not calculate out) If you draw an imaginary line from the target to below you so that it would be level it would be shorter than 500 yards, lets say 250. You set your zero for 250 yards and you will be dead on. It is hard to explain without a diagram. But it works. BTW that is trigonomertry, not calculas. Granted you could probably use cal, but that is the long way, and academics like to go the long complex route instead of the simple one that always works. :wink:
 

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Discussion Starter #14
Ahh yes Pathagream theroum. I know that VERY well, its like 2nd nature to me.

a^2 + b^2 =c^2

plug in the variables, add the squares, then do squar roots. Very easy
 

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To add more chaos and increase the entropy of our Universe :)

If i'm not mistaking, G should be measured in m/s^2 (meters in second per second). It is acceleration, not speed, after all.

Recoil is right, the task could be painful. Simple case is when bullet is 'dot', having no direction of herself. If we ignore air resistance, we can easily calculate angle the bullet should be launched at, solving couple of equations, because accelerations in X and Y directions are constant:
X_to_travel = V_initial*cos(Angle) * t
Y_to_travel = V_initial*sin(Angle) * t + G*t*t/2

The problem Recoil pointed at is that it will never happen in real life, at least because bullet rotates herself in XY plane (not to mention it is fired from RIFLE, thus it rotates around its axis and increase complexity of trajectory curve - in Russian military it is called Deviation, but English word have other meaning), thus both components of acceleration vector are changed over time. Even that could be solved, it will just result differential equations instead of two lines i wrote above.
But will you do it in real-world situation? Simple math wont do, real math wont do - and indeed, quessing (logbook in hand) is our best alternative.
 

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I never took any math after high school and I really ain't that good at it (A pre-emptive "shaddup" to recoil here, my smart-ass sense is tingling :lol: )

But all this stuff is for what data books are for!

I'll just pick up a slope doper, shoot from hills, shoot uphill, and record the results on data cards. That way I can leave the math to the pros.
 

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Muzz, that is EXACTLY what i was told by my sergeant when i first took sniper rifle :)
 

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a marine's .02

ahh angled shooting.... ok, not a "sniper" by the school, but i've done a few shooting schools, an alot of angled shooting ( 25-40 degrees ) ... the big part of angled shooting is yes a^2 + b^2 = c^2.... your shooting the c line... say 500 yds, at a 15 * slope... ok - take 500 x .98 (the cosine for the angle) and the bullet is gonna have a flight path like it was going for 480 yds - not 500. this is because yes it is traveling 500 yds from your rifle, but it is effected by gravity for only the b line... this help anyone? the way it was explained to me at my dm instructor course, and it has worked for a couple of years now. just my .02 - ok, i'll go back to watching now.
 

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firstly id like to say, i was using 10 as a speed to keep the math simple, but if you must be precise gravity is, at the equator is 9.78033 m/s² whereas the ave across the earth is 9.80665 m/s²

and yah recoil i was thinking 2 dimensionaly, but if you(not just recoil) note i did mention negating air resistance just to keep the math comprehendable

but if you think about it, if a bullet is in the air for multiple seconds, its going to drop alot naturaly... just check SCs own handy ballistic charts... a U.S. M2 .50BMG - 709gr FMJ-BT at 2850fps drops 404inches at 1500 yards...

im not saying i was right, i admit i was wrong in this case because i was thinking only 2 dimensionaly completely ignoring the fact a bullet spins lol

but yah the pathagorean theorum is god...you use it to replace an assload of formulas in math if you know how to manipulate it, such as distance, midpoint, etc etc
 
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