MOA vs MIL. In scope ajustments?

[jwp475]

A minute of angle is 1/60 of one degree. I have no idea when or how that term originated. Nineth grade geometry is where I learned about it, for the first time and that was a long time ago. Or was it tenth grade geometry?

 

[Eaglet]

Now thats coollight bulb. Where can I find these kind of math? That is a hugh differance. Idont understand, or how they came up with minute as a math turm? Can someone rec. a book or mag that can explain these terms in use? Thanks Bill Maylor.

Bill, do a search on this site and you will find just about anything you want. If you don't, I know there's a bunch of folks here including my self that are more than willing to share what little they know. As jwp475 said it, "none of us were born knowing anything". Your remind me of my self when I was much younger, boy did I want to learn, but I did not have what we have today; the internet and great sites like LongRangeHunting.com

 

[dmgreene]

Eaglet I found an easier way to deal with the .047". Say your target is 18" and you get a reading of 2 moa. 18 divided by 2=900 yards. Now subtract 5 yards for every 100 yards, in this case 9x5 =40. So you say 900-40=860 yards. If you say
17.19198 divided by 2 you come up with 859.599 yards. Thats pretty close huh? This is what I like about the moa system, I can do all the math in my head and for me 3.6 inches is just hard to deal with.

David

 

[Eaglet]

Eaglet I found an easier way to deal with the .047". Say your target is 18" and you get a reading of 2 moa. 18 divided by 2=900 yards. Now subtract 5 yards for every 100 yards, in this case 9x5 =40. So you say 900-40=860 yards. If you say
17.19198 divided by 2 you come up with 859.599 yards. Thats pretty close huh? This is what I like about the moa system, I can do all the math in my head and for me 3.6 inches is just hard to deal with.
David

David, that's definately much closer. 900-45 = 855 yards. to 860 that's only 5 yards. With a flat shooting rifle it would not be an issue. Just better to use a good rangefinder.

 

[Bill Maylor]

Eaglet, dmgreene, Thanks for the range math. I will try my hand next week with this math. I will bring a calculator to ck myself. I still have not recieved my NF for the 300RUM, but will try it with my 22-250. Fay just went over my head. The weather will calm down in a few days. I am not ready for wind or spin drift yeat. This is realy cool stuff, thanks guys. Bill Maylor

 

[sscoyote]

Bill, long-range shooting is a kick, and u've come to the right place for info., no doubt. The best way to understand reticle-rangefinding is to go right to the most basic formula. This way it becomes aparent that it can be used with any reticle (even archery sight pins if 1 wanted to), and u can also use it to calculate tgt. size, and easily see it's limitations as well. Here's the formula in it's most basic form (inches to yds.)--

tgt. size x range of reticle subtension measurement (usually 100 yds.) / reticle subtension (inches) / quantitity of gap tgt. occupies (decimal equivalent) = range (yds.)

...looks complicated but super-easy to apply. Here's the equation for an 18" deer that occupies 2.4 mils--

18 x 100 / 3.6 / 2.4 = 208

Recently at a long-range shoot one of the guys wanted to know how big the rectangular 1000 yd. tgt. was. We were using a mil-dot reticle that measured 2.1 inch per hundred yds. between dots at a higher power than what the mil was cald. for. The tgt. occupied 0.9 mils. Here's the equation making the tgt. size the unknown--

X" x 100 / 2.1 / 0.9 = 1000

X=18.9" when we went downrange and measured it it was 19.2". It just amazes me whenever i use this stuff just what can be accomplished with it. Now if we'd have known the tgt. size was 19.2" we would have got this range using the reticle if we didn't know it--

19.2 x 100 / 2.1 / 0.9 = 1016 yds.

Later a doe antelope ran by us and i thought to attempt to range it thru the reticle. It looked like it should be 1.8 mils just loping along, and it lasered at 362 yds. Using 14" as an "avg. back to brisket here it is--

14 x 100 / 2.1 / 1.8 = 370

Usually we can easily get within 3% of lasered with most reticles on hard tgts.

Nice thing about this form of the equation is that if u're after 1 tgt. size u can make the 1st 3 variables a factor. so for an antelope doe-- 14 x 100 / 2.1 = 667 this makes it quicker and easier to calculate.

I often put the subtensions of my reticles in the turret covers on a sticker just in case i need them.

Once u play around with the equation some it's very easy to memorize it, and even if u invert the bottom 2 divisors u'll still get the same range. This stuff is fun to play with, and is especially useful with simple plex reticles.

 

[dmgreene]

Thanks Eaglet, 9x5 does equal 45light bulb, not 40 I've been going a little stir crazy today, been pacing around the house because of Faye(the storm, not my wife). It has rained all day here. I agree with you on using a range finder instead of using the reticle also, I only use a reticle for ranging on non living targets. For reticle ranging to work you have to know the exact size of the target. Animals are constantly moving and standing at awkward angles which also makes it hard to use at extended distances.

David

 

[Eaglet]

Thanks Eaglet, 9x5 does equal 45light bulb, not 40 I've been going a little stir crazy today, been pacing around the house because of Faye(the storm, not my wife).

That's funny!

It has rained all day here. I agree with you on using a range finder instead of using the reticle also, I only use a reticle for ranging on non living targets.

Plus it's a lot of fun using it.

For reticle ranging to work you have to know the exact size of the target. Animals are constantly moving and standing at awkward angles which also makes it hard to use at extended distances.

David

It's also cool being able to know the size of a rock by using the range finder and then the mildot or moa system as sscoyote was explaing. It's all a lot of fun!

 

[Bill Maylor]

Thanks guys, this is a great start. The deer I hunt, on the wall mesured 16+- on the mount. Deer in NW FL. are not as big or as deep as some other states. I would like to see one 18+, and if I do I hope I dont miss. So I starting with 16" or 15.281757 as MOA target size. I mighthave to duck tape a calulator to my gun stock. So let the fun begin. Bill Maylor.

 

[Eaglet]

Thanks guys, this is a great start. The deer I hunt, on the wall mesured 16+- on the mount. Deer in NW FL. are not as big or as deep as some other states. I would like to see one 18+, and if I do I hope I dont miss. So I starting with 16" or 15.281757 as MOA target size. I mighthave to duck tape a calulator to my gun stock. So let the fun begin. Bill Maylor.

Good luck to you!
Another alternative is this:
1 MOA = 1.047" at 100 yds. Some foks believe 1" is close enough. Well, not always, not in all cases.
Here is why, 1" is substained in a MOA at 95.511 yads, not at 100 yards. You can see the error right there. So the alternative would be using 95.511 yds which will not change instead of dividing the target size by 1.047 every time. Here is an example.

Target size = 18"
MOA READING=3.5
(18/3.5)95.511=491.2 YARDS.
The other way:
(18/1.047)=17.1920
17.1920/3.5*100=491.2 yards.

The difference is that all you have to memorize is the 95.511 and just use whatever target size it is in inches.

Target size 16" MOA READING=2.5
(16/3.5)*95.511=611.27 yards.
The other way:
16/1.047=15.28176
15.28176/2.5*100=611.27 yards.

Target size = 12"
MOA READING=1.5
12/1.5*95.511=764.09 yards.
The other way:
12/1.047=11.4613
11.4613/1.5*100=764.09 yards.

Using the last example let's back it up into finding out what the target size is if you know the distance. Let's say our range finder says your target is at 764 yads (last example), a square box, and we want to know the dimensions of the box or the size of the rock or whatever. Here is how we do it:

764*1.5/95.511=11.999" -----CLOSE ENOUGH!!!

As seen above, take your ranged distance, multiply it by the MOA reading and divide it by 95.511 and it will give you the dimension of the target.

I hope this helps intead of confuse. Good Shooting and Hunting!!!

 

[sscoyote]

I think that's 1 of the reasons that guys don't use this stuff more often is that there are so many permutations to the formula that it gets confusing. I remember when i was researching the mil-ranging formula i was getting so many different variations of it that i couldn't get it right in my head. I was looking at the Nikon catalog 1 day and they advertised the mil-ranging formula using a factor of 27.77. For the life of me i couldn't figure out where that factor was coming from, then it dawned on me when someone said that's 100/3.6" (what i like to refer to now as the "subtension unit"). I started to wonder then what wuld happen if i just substituted the measurement of a simple plex or ballistic plex into it. Sure enuf it worked, frequently quite accurately too.

IMO, the real advantage to reticle-rangefinding is the fact that it can be performed with any reticle really.

 

[dmgreene]

Bill if you use 16 inches and the target reads 3 moa ranging with a moa reticle,
the way I do the math is like this: 16 divided by 3 equals 5.33 or 533 yards. 5 yards for every hundred would be 5x5=25. Subtract the 25 from 533 and you come with 508 yards as you final range. If you use 15.28175 divided by 3 you come up with 5.0939 or 509 yards. I can do the first method in my head and I don't have to remember what the target size is converted to moa.
If you are hunting NW Florida you probably have about the same size deer we have here in SW Alabama. 16 inches will probably be a little to much unless he is a 200 lb or better deer. I believe 15" will work for 175 lb deer. I do use the reticle for a quick check. If a deer will bracket inside 3 moa then its time to get the range finder, if the deer is bigger than 3 moa I put the cross hairs on the shoulder and pull the trigger.

David

 

[Bill Maylor]

Eaglet, you seem to have your math spot on . dmgreene you have the simplest way to do the math. Eaglet, I like the reverse on sizeing the target. Let me tellya, I JUST GOT A MATH LESSION and didnt fall a sleep.I am a plumber and the 95.511 is close to the 45`1.411 which I use almost every day. So this is easy for me to remember. I still need to know more about the MOA increases for increased distance. Im sure their is lots of ways to figure this. I did find a site today talking to Zeiss that makes target knobs set up custom or standard factory ammo and barral length,ect. that can replace stock knobs. I was looking for info on how to use Z-Plex for ranging. they make lots of knobs for all kinds of scopes. you can find these knobs at www.kentonindustries.com . Looks to me these could be knobs for dummy's. I was impressed. Bill Maylor

 

[Johnny Boy]

I think MOA math is easier for ranging. Just take the size of target and divide by the number of MOA's it's subtends then multiply by 100.

So say you see a mule deer, which average 18" from bottom of chest to top of back, and this measures 3.7 MOA's in your scope. Divide 18 by 3.7. You get 4.86. Your range is 486 yards. Of course, the farther the animal, the less accurate it becomes. If your rangefinder is forgotten back in the truck, this method would work in a pinch.

If you have a good drop chart and rangefinder... then I think both work equally well.

How do you get the 3.7 MOA in the scope? Do you need to set the power to the max on the scope? Help, this is really interesting. I am a newbie, just like Bill Mayor in long range shooting, but I am not new to reloading.

Johnny