Meters,Yards and Mil-Dots,tricks of the trade,add yours!!!

Mildot Windows

http://2.bp.########.com/_bP_PNTfFn9I/Sk6vi7SeilI/AAAAAAAAAGc/QH0e3H7MzSk/s400/window.JPG
On a mildot reticle there is a square area covered by the thin crosshairs which is 10 mils across. Let's call this the "Big Window". The Big Window is divided into 4 "Small windows". The Big Window is one yard across at 100 yards, Small window 18" at 100 yards. The Big Window is one foot across at 100 feet, Small window 6" at 100 yards. The Big Window is one meter across at 100 meters, Small window 500mm at 100 m. If this is all you can remember, you can do rangefinding if something on the target is a foot across, a yard across, 6" across and so on. Plus on "2nd focal plane" mildot scopes, the area covered by the Big Window is changed by the Zoom knob. So you can turn the Zoom knob down to get a 50" Big window at 100 yards (make a note of this zoom setting), with each mildot covering 5" @ 100 yards. Or a 40" Big window. Or whatever suits you. So you have a rangefinder you can actually remember how to use. Note: First focal plane reticles zoom in sync with the target, so the Big Window always covers the same area at a given range.

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Mildot Rangefinding, Laser Rangefinders and The Danger Zone
 
MilDot Field Items and Measurements

Some rural items from dope pages.

30" Corn Row widths(good for lead and wind)
18" Diameter Disc blades(regular size. can go be up to 36")
48" Tall Orange snow fencing, plastic
34" tall 55 gal. oil drum
14" tall x 36" long small sq. hay bale
4' tall small round hay bale
6' tall large round hay bale
7" tall rural mailbox
18" long rural mailbox
42" to the bottom edge of rural mailbox
45" tall pasture cattle hay ring
48" tall Aluminum pasture gate
 
I use MOA. mils is good but I found it was too complicated. What is the measure of yur mik-dot reticle? US army. US marines, or acutal mils? Moa is simple. Target hieght in inches divided by moa multiplied by 95.5.
 
gunny198 said:
I use MOA. mils is good but I found it was too complicated. What is the measure of yur mik-dot reticle? US army. US marines, or acutal mils? Moa is simple. Target hieght in inches divided by moa multiplied by 95.5.
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Mil is:

Distance = Target height / height in mils x 1000

If you use meters for your target height, the answer is in meters, if you use yards, then the answer is in yards.
 
Those that shot precision rifle matches with me know that I do well in moving target matches. I'm often asked about the techniques I use (tracking vs. trapping, etc...) and one of the question that always comes up is how much do I lead the targets? To which I give an answer that is an angular value in mils. People are usually expecting my answer to be in inches, so this typically leads to another question about how much I adjust for different target speeds and different distances. When I reply that I only adjust for speed, that distance doesn't matter, this usually causes some confusion and disbelief.

It doesn't make any real difference in a match that is shot at known distance with a target that always moves at the same speed, but it does make a difference in real world applications, and I like doing things in ways that are usable off the range. So, I've created a few charts to try and illustrate how this works, and to maybe shed some light on one of the reasons why there is a big push towards first focal plane in tactical scopes.

Here is a charts that show the required target lead in inches for you typical 308 175 SMK load:

308_inch.jpg


It's what you would expect: the faster the target is going and the further away it is, the more lead is needed. The movers are typically going at 1-1.5 MPH in the matches.


Here what it looks like if you convert those leads to mils:

308_mil.jpg


Notice that for a given target speed, the lead in mils stays almost constant over a large distance. That is something that can be taken advantages of.

The thing you need to realize is that since it is an angle, differences in value make less of a difference at closer distances than they do at longer ones. So, if you wanted to use a single lead value for a particular target speed over a large distance, it makes sense to choose one from one of the farther distances.


Lets say we used the following values for different target speeds over the the entire 100-500 yard range:

308_lead_chart.jpg


If we predicted the target speed accurately and did our tracking or trapping properly, we would get the following errors:

308_error.jpg


These are pretty small, and if everything else was done correctly (wind call, hold, etc...) and the load was accurate, they would result in a hit. This works for any caliber, and the shorter the flight time of the bullet, the less error there will be and the larger the range of distance this will work over.

This is what the 6mm Crusader that I have been shooting this summer looks like:

Leads in inches:

DTAC_inch.jpg


Lead in mils:

DTAC_mil.jpg


Lead table that I use over distance, and the resulting errors:

DTAC_lead_chart.jpg


DTAC_error.jpg


Note that there is less error than the 308 load because of the reduced flight time.

Now, target speed is like wind: the best you can ever do is estimate it, fire a shot and make corrections (if possible). It is going to be an estimate regardless of which way you lead. The advantage to using the angular lead method is that your solution table looks like this:

DTAC_lead_chart.jpg


versus this:

DTAC_inch.jpg


Its one dimensional vs two and is far easier to memorize and use since you only need to consider one thing: target speed. With a good reticle it can be done accurately, and in an FFP scope, you can do it at any magnification.

The other advantage is that you're focusing on the part of the target that you want to hit and not some space out in front of it. This typically helps with vertical deviation and you can often catch your own swirl and splash (if you use a break). The size of your target doesn't matter either. If your linear hold-off is not with respect to the desired point of impact, but rather to the edge of the target, another error is introduce if your target can vary in size or orientation.
 
kombayotch that is very detailed ... thanks ... something to give a lot of thought to. I found that when I was testing optics though that the 1 and only fault I had with ffp was that at distance (800+ meters) at high magnification the cross hairs obscure much of the targets impact zone, which is also the reason I went with the NF mlr reticle so that the mils were gradient with thin lines compared with dots, therefor providing many "cross hairs" when aiming off. And I also agree that mils are much easier for doing math in ones head ... 1 mil = 10cm at 100 m so adjusting math on 1/10 increments ... 1 cm per click per 100 m ... can't get much easier on the grey matter.
 
Depends on the scope. I've never had any problems hitting small things with my Premier Gen2 XR reticle. Routinely use bullet holes for aiming points at 300 yards.

Clarity of the optic also plays a role...
 
I use mil dot calc on my andriod galaxy nexus. No math, just plug and play. Great teacher for testing your math in your head. Metric/imperial moa/milRads for inputs and outputs. Can't lose with this.
 
Down load JBM ballistics on your iPhone and let it do the math lol
I have a good one for wind with a .308 you take the range say 1000 yards minus 1 so that gives you 9 with 10 mph full value than you take out some for wind angle say half value wind so 9 % 2 = 4.5 and then add or minus for wind speed say it was actually 20 mph you would double the 4.5 back to 9 ... 9 MOA for a 20mph wind 1000 yards half value this will get you close with a .308 175 smk and they say for a .223 it's the same only you don't minus 1 from the range ex. 500y 10mph full value cross wind would be 5 MOA for the .223 or 4moa for a .308 ... This is only to get you close fine tuning may be required
 
There is an extremely accurate way to get distance to tgt out to 800m. Use your side focus paralax adjustment. It works. It's numbered with increments and all you need to do is slowly turn it til the tgt becomes crisp.I did an entire determining distance exercise with our S and B 5-25s out to 800m like this.
 
swissinn said:
There is an extremely accurate way to get distance to tgt out to 800m. Use your side focus paralax adjustment. It works. It's numbered with increments and all you need to do is slowly turn it til the tgt becomes crisp.I did an entire determining distance exercise with our S and B 5-25s out to 800m like this.
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I often wondered about this. Would it work if someone with crappy eyes, or better eyes than you used your kit?
 
swissinn said:
There is an extremely accurate way to get distance to tgt out to 800m. Use your side focus paralax adjustment. It works. It's numbered with increments and all you need to do is slowly turn it til the tgt becomes crisp.I did an entire determining distance exercise with our S and B 5-25s out to 800m like this.
Click to expand...

On my pmii I have to have the knob like turned 30% past 100m for 100m, same for 200. Not sure how accurate that is. I suppose you'll get close enough to guesstimate? Ie 100M shown vs 70m actual.

Not disputing your facts, just trying to understand.
 
bsand said:
On my pmii I have to have the knob like turned 30% past 100m for 100m, same for 200. Not sure how accurate that is. I suppose you'll get close enough to guesstimate? Ie 100M shown vs 70m actual.

Not disputing your facts, just trying to understand.
Click to expand...



Jordan Smith said:
Most scopes are not perfectly accurately labeled for parallax distance. You just adjust the knob until parallax is gone, ignoring the numbers on the dial.
Click to expand...

This
 
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