[LSUfreak25]

Sort of like "These amps go up to 11"? THAT'S what I was getting at in the music thread by the way. I figured someone who's seen "This is Spinal Tap" would have said something. I'll keep an eye out for this one though, glad you brought that up on that off chance the thing spreads at all. If the dot doesn't cover "1 mil" (which he makes it sound like it wouldn't) , is it really even a "Mildot"? I would guess not.

I know this has nothing to do with the topic, but just in case you thought people were lying to you, they really do have Amps that go to 11! POD's guitarist uses one. I had a great opportunity to play with them at New Orleans Voodoo Fest in 2003, so I got to see it. + it is a special order amp, you can't just go buy one.

 

[Kaz]

Sort of like "These amps go up to 11"? THAT'S what I was getting at in the music thread by the way. I figured someone who's seen "This is Spinal Tap" would have said something. I'll keep an eye out for this one though, glad you brought that up on that off chance the thing spreads at all. If the dot doesn't cover "1 mil" (which he makes it sound like it wouldn't) , is it really even a "Mildot"? I would guess not.

I know this has nothing to do with the topic, but just in case you thought people were lying to you, they really do have Amps that go to 11! POD's guitarist uses one. I had a great opportunity to play with them at New Orleans Voodoo Fest in 2003, so I got to see it. + it is a special order amp, you can't just go buy one.

Cool 8) Anyway, back to mildots.

 

[STINGER]

Ah yes, exactly! I was/am trying to come up with the reason WHY we only use the baseline when in fact the time of flight (which is the time gravity has to act on the bullet) remains the same, but drop is less. But, this is why if you esitmate your range with a map/gps you will NOT have to figure slope dope. A bino company actually contacted me about 1.5 years ago with a laser range finder that actually computer horizonal range as well as direct line range. It was a great concept, but they never contacted me with a production version. Perhaps another company has come up with the same thing.

I know there are a few physics experts that frequent this forum, I'm hoping one of them can explain the physics behind why the baseline is used.

MEL

mel

optilogic did in fact bring out and still produce a rangefinder/inclinometer.

thought you might be interested.

 

[mele]

Yes, leupolds new LRF has this feature also, as does pentax's (I believe)

MEL

 

[Engineer]

1MOA = 3.44 Mil millitary uses 6400 mils / 360 degrees, but math says that there are 6,283.18 mils / 360 degrees

 

[Jackal]

It has nothing to do with power, and EVERYTHING to do with milradian measurements.

On most scopes the mil-dots are only accurate at a certain power. 10x or 16x, etc. YOU MUST MEASURE YOUR TARGET IN MILS WHILE YOUR SCOPE IS AT THIS CALIBRATED SETTING. Its all about measuring accurate mils. Of course, if your scope is calibrated for mils at 10x, you could power to 5x and then each mil-dot would measure 2 MILS. Again, its all about accurate mil measurements

MEL

Above understood. Somebody else mentioned that the calibrated setting should be listed in the literature that came with the scope and even calling the manufacturer. Well enough.

I just received a Zeiss Conquest 6.5-20x50AO scope w/MilDot reticle. The literature for this scope reads

Your riflescope is equippped with a reticle of your choice. The reticles of all Conquest riflescopes (except the 3-12x56) are located in the second image plane. In these riflescopes, only the size of the target changes when the power is changed, and not the reticle size. For this reason, range estimation with the reticles in the second image plane must always be conducted on a consistent power.

Unfortunately, the literature does not mention what power setting that should be.

I wrote to the folks at Zeiss with questions about that and received a response that essentially avoided the answer. The fellow who responded basically sent me some documents on how to use a MilDot scope. Very nearly the same documents are already posted on the internet, thank you very much. Ugh!

Practically all the documentation I've seen on range estimation with a MilDot scope quote the distance between MilDots as being 3.6 MOA at 10X magnification. I can live with that.

Given the above, does anyone know the actual magnification setting that variable power Zeiss scopes should be set at for range estimation or is it a fair bet that 10X magnification is correct?

Thanks in advance for your replies and cheers!

 

[mele]

The proper setting on the zeiss conquest is 10x for the mil-dots. A simple test would be to go to a measured 100 yard range, put up a piece of paper with two large and visible lines 10.8" apart and it should line up on 3 mils. (or use whatever variable of 3.6 per mil you want).

MEL

 

[Jackal]

The proper setting on the zeiss conquest is 10x for the mil-dots. A simple test would be to go to a measured 100 yard range, put up a piece of paper with two large and visible lines 10.8" apart and it should line up on 3 mils. (or use whatever variable of 3.6 per mil you want).

MEL

MEL, thanks for the reply. I sure appreciate it.

And yes, as a last resort, that's more or less what I had planned on doing. Have targets that are 1 mil in size @ 100 yards to look at. Suppose can stack them as well.

Sent another note to Zeiss requesting they verify range estimation should be done at 10X magnification if for no other reason than documentation from the manufacturer.

Cheers!

 

[Jackal]

The proper setting on the zeiss conquest is 10x for the mil-dots. A simple test would be to go to a measured 100 yard range, put up a piece of paper with two large and visible lines 10.8" apart and it should line up on 3 mils. (or use whatever variable of 3.6 per mil you want).

MEL

You were right. Finally made it to the range today. Had a 3.6" target just for MilDots copied from another site linked hereabouts. Framed perfect @ 10X. Now, if I can just do my part, I can finish getting that puppy properly sighted in.

 

[Millett]

Mil dot

Good site is www.mil-dot.com

explains the use and has a game to learn how to use the mil dot.

Millett has a new design called Mil dotbar that uses a standard dot and then a bar so its easy to align up the rangeing of the mil dots.

Good shooting

Steve

 

[Jackal]

Rgr that. Had been to that site previously.

 

[barnhill308]

Some people think the MIL in MIL-DOT stands for MILITARY.... *TAKES A HUGE BREATH*..... The "Mil" in "Mil-Dot" does not stand for "Military".... it stands for "milliradian." The radian is a unitless measure which is equivalent in use to degrees. It tells you how far around a circle you have gone. 2 PI radians = 360 degrees. Using 3.14 as the value of PI, 6.28 radians take you all the way around a circle. Using a cartesian coordinate system, you can use "x"- and "y"-values to define any point on the plane. Radians are used in a coordinate system called "polar coordinates." A point on the plane is defined, in the polar coordinate system, using the radian and the radius. The radian defines the amount of rotation and the radius gives the distance from the origin (in a negative or positive direction). ANYWAY, the radian is another measurement of rotation (the degree/minute/second-system being the first). This is the system used in the mil-dot reticle. We use the same equation that we used before, but, instead of your calculator being in "degree" mode, switch it to "radian" mode. One milliradian = 1/1000 (.001) radians. So, type .001 into your calculator and hit the "tangent" button. Then multiply this by "distance to the target." Finally, multiply this by 36 to get inches subtended at the given distance. With the calculator in "radian" mode, type:
tangent(.001)*100*36 = 3.6000012". One milliradian is just over 3.6 inches at 100 yards. If you estimate... two milliradians equal about 6 feet at one-thousand yards. The mil-dot reticle was designed around the measurement unit of the milliradian. The dots, themselves, were designed with this in mind and the spacing of the dots was also based upon the milliradian. This allows the shooter to calculate the distance to an object of known height or width. Height of the target in yards divided by the height of the target in milliradians multiplied by 1000 equals the distance to the target in yards. For example, take a 6-foot-tall man (2 yards). Let's say that the top of his head lines up with one dot and his feet line up four dots down. So: (2/4)*1000 = 500 yards away. This same tecnique can be used to estimate lead on a moving target or to compensate for deflection on a windy day. The distance from the center of one dot to the center of the next dot is 1 milliradian. We are told (by the folks at Leupold) that the length of a dot is 1/4 milliradian or 3/4 MOA (Given this much information, one can determine that the distance between dots is 3/4 milliradian.).* I use the term "length" because the mil-dot is not round. It is oblong. The "dots" on the verticle crosshair run oblong in the vertical direction. The dots on the horizontal crosshair run oblong in the horizontal direction (i.e., they are lying on their sides). The width of each dot is an arbitrary distance and is not used for any practical purpose. Like a duplex reticle, the mil-dot reticle is thicker towards the edges and uses thin lines in the middle where the dots are located and the crosshairs cross. The distance between the opposite thick portions is 10 milliradians.

i understand how you get the 500 yards with the 2/4 x 1000. but say you have a target at 400 yard how many mill dots do you go down to put on the target.

 

[Guest]

"I know there are a few physics experts that frequent this forum, I'm hoping one of them can explain the physics behind why the baseline is used.

MEL"


Like most things in precision shooting, there is a right way, and a wrong way to do things. By clicking on the link below, you can see the graph that Pejsa uses to illustrate the correct physics.


http://artactical.com/eve/forums/a/tpc/ ... 609536/p/2





Actually, the basline is not used to get the correct adjustment for inclination angle shooting, even though it is a popular and misguided methodology.



The above link shows a graph done by Pejsa, Mr. Inertial Guidance, who personally developed the reentry Guidance system for the Space Shuttle. He also flew B29's (30 combat missions) and led a team of guys at Thor that built the first working inertial guidance system for long range missiles, similar stuff on the Titan II ICBM as well. Three Air Medals, Distinguished Flying Cross, and a Presidential Citation.

The graph shows a couple of things. First, that gravity is a constant, and drop from borline on the line of gravity's force vector is the same, even though the trajectory's angle varies. Second, it shows that geometry can provide a decent solution to inclination angle problems. Pejsa uses the correct math ( 1-cosine ) for his correction factor as do all educated folks.

This graph for simplicity's sake, assumes that borline and sightline are the same, he probably should have written borline instead of Line of Sight on the graph to avoid confusion. On the same page as the graph, right above figure 6 are the words, "Suppose that we adopt a method where we sight down the Borline. Line of sight through the bore or the 'Original Vector' without the effect of gravitational force is the obvious intent.

It is no small thing to note that, the Actual Correction is a specific distance PERPENDICULAR to the borline, and on that perpendicular line, the exact distance between the original borline and the actual trajectory.

Once the shooter understands that the force of gravity is a constant at a given altitude, and that bullet drop stays the same at a given range relative to the vector of gravitational force, the rest is just a very simple geometry equation.

Anyone interested in learning the correct way to build data for inclination angle shooting can click on the link above and go to the first page of that thread. I walk the shooter through the process and then give specific example of how most use the wrong math, what error it will produce in the real world, and then the right way of getting an exact firing solution.

 

[timdgarry]

Mil Dot Cosine

hey,

just to reiterate on what ballistic said, not that it was a bad description, but to offer a more cut and dry equation/explanation here you go

COS(deg) = hyp/adj

thus to solve for your hypotenuse(the diagonal) you take the cos of the angle multiplied by the adjacent(baseline)

also you can use SIN(deg) = hyp/opp

which means if you have the angle degree and the distance above the target then you can solve the same way, by multiplying the angle degree but SIN, then multiplying that by how high above the target you are

In Trig 4/5 of a lifetime ago, we learned
Oscar
Had
A
Heap
OF
Apples

Oppisite over Hypotenuse = Sine
Adjacent over Hypotenuse = Cosine
Opposite over Adjacent = Tangent

So I think you are mistaken on the Cosine Formula above.

 

[Xelera]

Older thread, but just found it while killing time awake tonight...

The reason the baseline distance is used, vice the straight line of sight distance is as follows...

If a bullet is fired horizontal to the ground (no slope) gravity acts on the bullet in the straight downward direction at roughly 32ft/sec^2, so for this example, essentially, all the force of gravity is applied to change the bullet's trajectory, and none to changing its velocity. Consider this firing a bullet along the x-axis of a graph.

Now if you fired a bullet vertically, straight up (they Y-axis of a graph) the bullet is experiencing the force of gravity as a change in its velocity (again, at roughly 32ft/sec^2) but having no effect on its trajectory (the bullet is flying straight up, will continue to do so until it uses up all of its velocity, and fall straight back down). There is no "drop" from straight line distance in this plane.

Now think of a bullet fired on a trajectory somewhere between the Y-axis (straight up) and the x-axis (straight out). This will present a combination of the 2 effects, deceleration and change of trajectory. Obviously, the change in trajectory is 0 at one angle (vertical) and maximum at the other angle (horizontal) for a given distance/initial speed. And to make these two forces unify, its some in between value, for a bullet fired at an angle.

Now finally, assume you took a segment along the x-axis = 300 yards, and measured the bullet change in trajectory along that path. Then take the same 300 yard segment along the y-axis, and note there is no change in trajectory from the straight-line path. Now take the same 300 yard segment, at an angle in between the x and y-axis, and the change in trajectory should be between the full value along the x-axis and the zero value along the y-axis.

This is where you grade school geometry comes in... Remember, for the 3 measurements you just made, the straight line distance was constant between them. So if the x-axis is full value of deflection, the angled shot in between has some lesser angle of deflection, and this is where you draw your triangle, from the origin of the graph (0,0). Assume its a 45 degree up angle shot, so draw your line with a slope of 1 (rise over run = 1/1 =1). when you get to your 300 yard segment, draw a straight line down to intersect with your x-axis, and this shorter than 300 yard point on the x-axis is the actual drop distance that gravity affected it, per the above discussion, at a lesser than full drop value.

Hope this helps... its after 5am here and i've been at work all night, 12 hour shift... but it makes perfect sense to me right now as i'm writing it!

 

[Kdiver58]

Now I've done it

Life was simple and fine with my 10x Falcon Menace .. Now I'm messing myself up with the 4.5 x 18. I understand that I can only range estimate with the new scope at 10x and be mil dot accurate ..... BUT !!!

I frequently play around using only the mil dots (3.438 MOA per mil dot) and my dope charts for rapid target acquisition. I know that 10x is the only setting I can range estimate at but can I use the mil dots instead of dialing in dope at any setting since the mil dot is only being used for setting the hold over ????? Can't seem to get my head wrapped around this one ... Sorry .. K

 

[mele]

It is the same if you are using the dots for hold overs as when you zoom in (and out) you are increasing or decreasing the amount of viewed space between the dots. So, your holdover numbers will also only be accurate at 10x.

MEL

 

[Fatty]

It is the same if you are using the dots for hold overs as when you zoom in (and out) you are increasing or decreasing the amount of viewed space between the dots. So, your holdover numbers will also only be accurate at 10x.

MEL

Or if you're too lazy, too dumb or just have too much money laying around (or all of the above) then get a First Focal Plane (FFP) scope. That way the reticle size changes accordingly with the image size and you can range at any mangification.

 

[Xelera]

Correct me if I'm wrong, but you can use a second focal plane scope for range estimation at more than just its one calibrated setting.

Example, say your sfp scope goes up to 15 power, but its only calibrated at 10x... with the scope on 10 power, your equation (using good old american standard yards) is

(target size in yds)*(1000)/(mil-dots covered by target) = range in yds

now if you put your scope on 15x, you simply use that same equation, but multiply the final answer by 1.5... if your scope goes to 20x, then you multiply the final answer by 2.0... and for an 18x, obviously, its 1.8... since most scopes are calibrated on the 10x scale, its a ratio of the scale you are on, to the scale you are calibrated for.

if you remember your order of operations, you can make it easier still. lets go back to the 18x scale. you really like being as close in on your target as you can, for accurate mildot ranging, so this is the one you find yourself always using... fine, instead of multiplying the target size (in yds) by 1000, just change it to 1800 all the time.

not a seasoned shooter, but im halfway decent at math...

 

[I Dares I Wins]

mil dot

1 mil equals 1/6400 of a circle, which equals 1yd at 1000yds