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Discussion Starter #1
I've searched the forum, but it seems everyone already knows what this is. :wink:

Scatch Maroo
 

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Heh scatch.....mil dot is a standrd fine crosshair with dots spaced verticaly and horizontaly at set intervals which are used for range finding and hold-over, or lead / windage.
Check out any tactical scope sites via Google.
 

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First resource, check snipercentral.com FAQ:
http://www.snipercentral.com/faq.htm

More precisely, a mil-dot is representing one mil-radian, which represents 1 unit of measure at 1000 units of measure. It was developed for artillery use initially, and has been extremely useful for sniping. It is used for range finding. If you know the size of your target, and have a way to measure milradians, then you can estimate the range to the target.

MEL
 

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mele said:
If you know the size of your target, and have a way to measure milradians, then you can estimate the range to the target.
What would a person use to measure milradians?

Scatch Maroo
 

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Discussion Starter #6
Is a PDA and such software necessary for accurate shots, or are their methods one can employ in the field minus all of these fancy gizmos and still be as accurate?

Scatch Maroo
 

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Scratch, the scope itself has milliradian measurements built into it. The dots that Kiwi is talking about are spaced such that each dot is 1 mil away from the next one along the same axis.

As Mel said, if you can estimate the size of your target (in meters or centimeters), you can use the size (in milliradians) of the target in your scope to estimate the distance (in meters) to your target.
 

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I purchased a "Mildot Master" from SWAFA which is, in efect, a slide-rule calculator...no batteries!!

It allows quick and easy range measurment when used with your mil dot scope. Haveing your ballistic chart for the loads in use stuck on the chart, lets you dial-up your scope for bullet drop compensation....or use the dots themselves for hold-over.

The Mildot Master also has a great little up hill-down hill facility to calculate the compensation factorfor those shots.

Try www.riflescopes.com

cheers.
 

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Of course, the BEST way to estimate range is a laser range finder.

In terms of "slope dope" (uphill/downhill shooting) the best way to estimate range in those cases would be the use of a map IF you could get accurate enough (GPS marked points perhaps), as a range estimation done on a map would actually eliminate slope dope adjustments. The math to prove this is complex, but doable if anyone must see it...

MEL
 

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Discussion Starter #10
Shoe, Kiwi, much appreciate the info--I think shooting, rifling especially, has held my interest for so long because of the physics and math involved--very interesting stuff.

Mel, if you're not adverse to putting up the equation, I wouldn't mind seeing it... I like math a bit.

Scatch Maroo
 

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Mil Dot or W.E.R.M formula

Range calculations using MIL DOT are fairly simple:

Height of target (meters) x 1000
____________________________ = Range to target (Meters)

Observed target size (mils)


So if you have a 2 meter target 80" (6'8") with a mill spacing of 6 mils,

the range is 2 x 1000 /6 or .33 x 1000 or 330 meters.

You then adjust your elevation on a .308 up a little over 1 mil on the scale and fire holding on center of mass. Guaranteed hit!

Or, if you have a 1.5 meter target (60") and a mil measurement of 2 mils, the range is 1500/2 or 750 meters. Depending on the rifle you should come up around 14 moa.

:D
 
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I believe Scatch was looking for the slope dope formula I was referring too that would take out slope dope calculations as long as you know the true horizontal range (map or gps being the easiest way to find that).

I'm still trying to compose my thesis in a way that is easy to put on this board...

MEL
 

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Calculation of the range for bullet fall is fairly simple if you have a cosine table. Note that for small angles, the cos approaches 1.000 (say about 15 Degrees or less.)

 

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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
 

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Ah ha! It looks like the range finders that compensate for slope was in fact brought out by Pentax. The AC600 and AC800 models. I wonder if they just purchased the company I was talking to, as they disappeared.

MEL
 

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I'm no physics expert or any kind of expert for that matter but I know that the theory Mel is talking about holds true for archery range calculations also. My guess as to why is because gravity always pulls straight down no matter what angle your shooting at. Am I getting close? :?:
 

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More on External Ballistics

mele said:
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
Gravity is a force which acts on the bullet over a period of time. This force vector operates in a direction normal to the surface of the earth for the short distances that we shoot small arms

If you wish to calculate the time of flight then you need to know the horizontal component of the distance vector (the base line) which is parallel to the earth surface. Time of flight is Velocity/D cos(angle). Get the velocity during flight, you need the muzzle velocity, environmental conditions, shape of the bullet (C1, etc) wind conditions, etc.

Note that normal laser range finders or other methods of distance estimation only gives the actual distance to the target.

However, as you suggest Leica builds a LRF with built in angle compensation to about 35 degrees of angle. Known as the LEICA VECTOR, the last time I checked this device was about $7000. It is in wide use with ROMAD and other special forces. It has provision for interface with GPS equipment and radio for direct satellite uplink of targetting data.

Need more: Search External Ballistics Small arms
 

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Critter,

Thanks for the physics explaination! Its appreciated.

To add some emperical data to the theory, I engaged a target at about 30 degrees yesterday at 300 meters measured on the GPS (base line distance) and bingo, shots were dead on even though the line of site was further than 300 meters.

MEL
 

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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.
 

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What is the equation to find the distance of a target with a 10x scope?

I have read and heard about taking the known height of the target in yards dividing it by how many mils the target takes up and times by 1000. But wouldn't this equation work with a certain power only? Don't all powers have different equations? If anybody knows would you let me know what the equation would be for a 10x scope.

Thanks
 
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