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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2010 at 11:23
thumper5384 View Drop Down
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I have recently purchased a Mil Dot scope for my Winchester 7MM magnum and I was trying, unsuccessfully, to find a chart that would basically tell me the distance between Mil Dots at a known range.

I found some information on it but my scope has 6-24 magnification and I know the distance between dots changes with the zoom but I couldn't find anything that specifically said what the gap was for each zoom, or that even mentioned zoom for that matter.

Does anybody know where I could find a chart that I could reference or know some kind of formula I could use?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2010 at 11:30
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something like this?
 
Mil-Dot Master
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2010 at 12:26
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What kind of scope did you buy?  Exact model.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2010 at 12:28
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yea I saw that and I like the bullet drop factor on the side but again it doesn't tell me the distance between mil dot's at a known range and a specific zoom.  It doesn't say what the referance zoom is for the bullet drop on the right hand side.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2010 at 12:29
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it is a bsa scope but i don't know the exact model right now.  box is at home and i'm not right now.  i'll have to get that back to ya.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2010 at 12:51
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True Mil dots are 3.6 inchs apart at 100 yards. Double that 200 yards, triple at 300 yards and so on.  First though you need to find out what power your mag is set to show true mils though.  Many scopes that is the top mag range, but some scopes it is 10x or 12x.  That is why I wanted to know the exact model. 

I cannot find that info on the BSA website.  So you are probably going to have to figure out what power the mils are accurate on by yourself.

What you will need to do is set a target up at exactly 100 yards from the end of your scope.  Make it with lines exactly 3.6 inches apart and turn your mag back and forth til your dots line up perfectly with the lines you have made. 


Edited by supertool73 - October/19/2010 at 13:24
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2010 at 13:02
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thats really helpful man. thanks a lot.  i'll go home and look at my manual for the scope to make sure.

does anyone know the rate of change ratio when you zoom in or out for the mil dots?  for instance if they are 3.34 in apart at 10x mag at 100 yards, how far apart would they be at 100 yards at 15x mag or 20, or 6?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2010 at 13:19
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I would suggest one of three things, in order of what I would do if on a budget -
 
1.  Buy a fixed power mildot scope.  this takes out all guesswork, you know that it is set right and dont have to worry about what magnification you are on, it will be the same every time.  Plus, fixed means one less thing to adjust or break.
 
2.  Buy a FFP mil dot scope if you want variable.  FFP will keep the mil dots constant through all mag levels, but these are more expensive.  I am sure most here ill tell you to buy the Super Sniper 3-9 FFP, which is what I am doing after I sell one more scope. 
 
3.  Shoot the heck out of it at different ranges and different magnifications until you are good with it.  This can get expensive and time consuming in a hurry.
 
Of course with 1 and 2 you still need to shoot a lot and practice, but much less to learn and become proficient at.  With a 7mm mag though, I dont think you want to shoot more then you have to, and not sure how well that BSA will hold up to that recoil.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/19/2010 at 10:16
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I think I'm gonna take a spin off of supertool73's approach.  I think I'm gonna set up a paper target at 100 yrds with every inch marked in bold black and a big line to put my main cross hair on.  Then I'm gonna look at every magnification at 100 yrds and write down the distance between the dots for each mag. Then I should just have to double for 200 and triple for 300 so on.  I'll prolly do the same at 200 and 300 yards just to make sure the original calculations were right but I think  this might help me out.

I'm not wanting to use the scope as a range/size finder.  I have a rangefinder for that. I'm wanting to use it for my known bullet drop at a known distance so all I really want is a distance between the dots at the known range.

Thanks for all of the help, I really appreciate it.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/19/2010 at 11:43
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Originally posted by supertool73 supertool73 wrote:

True Mil dots are 3.43 inchs apart at 100 yards. Double that 200 yards, triple at 300 yards and so on.
That's not quite right. True mil dots are 1/1000th of the distance, e.g. 3.6" @ 100 yards (3600 inches). I think you're thinking of the number of MOA/per mil @ 100 yards (1.047" * 3.438 = 3.6").

If your scope is on its correct ranging power (SFP) or on any power for FFP scopes, the reticle sub-tensions should span exactly 3.6" each @ 100 yards. A mil-dot reticle should cover 1 yard @ 100 yards since it is 10 mils across. If the turrets are in mils, changing elevation or windage 1 mil should result in a shot (or if just viewing, a point of aim) 3.6" different.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/19/2010 at 13:07
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Yeah, you are right.  Good correction.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/22/2010 at 02:26
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Thumper, that optic should be marked on the power ring for the correct mil subtension. Most are--though not all. Best to dbl. check it at the range too as mentioned above. Once u figure out what power the dots are 3.6" per 100 yds. apart, u can go to most ballistics programs and they will have a bullet drop menu that has a mil-dot option. JBM ballistic program is one of the best.
Subtension is inversely proportional to magnification (assuming the power ring is calibrated correctly. Most are close enough for downrange zeroing purposes). In other words if the mil is cald. for 10x in a 6-24x optic it will be 1.8" per 100 yds. @ 20x. I never use my mil optics for either downrange zeroing or rangefinding at the 3.6 IPHY power. I always go higher and consequently more power and smaller subtension.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/22/2010 at 07:05
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Before we even start talking precision, may I suggest a better glass first, something other than B S A...
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/22/2010 at 07:48
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ranging and hold over with sfp are two different animals. the relationship between subtension and magnification is linear, it changes by the fraction of the lower power to the highest mag. Holdover is diffferent, you will find no material on the relationship at the various powers and the load you will be using, A good place to start is the mil relationship on the power it was designed for. As an example if the drop for your set up is 3 mil at 500 yds,for a scope at 24 it will be pretty close to 2 mil if you change the power to 12. This relationship changes with the power range of each scope used. How do I know this? Lots of shooting. A 12x scope when reduced  to 6 power won't show the same distance change in the reticle. It will be less than a mil, and probably harder to "mark" in the sight picture for holdover. This is a hard  path to take, but if you do, you will learn more about scopes and your rifle than shooting groups.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/22/2010 at 11:31
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Originally posted by VYD VYD wrote:

Before we even start talking precision, may I suggest a better glass first, something other than B S A...

Ya know... That's not particularly helpful. He has a  BSA scope.  It may not be your choice, but he chose it. Give the guy some help, if you can. Otherwise, don't tell him to pack sand until he buys something up to your standards. We're here to help, not to turn folks away.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/22/2010 at 13:20
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You are not helping either by saying this. The fact remains the same whether you like it or not: there is no precision in a BSA scope, especially when that scope is on the magnum. He is shooting 7mm which is not cheap to begin with. Sure I (and you) can "help." But I think others already said what needed to be said. All I am saying is that there is no way to be precise with equipment not designed to be precise. You can sugar coat it and give a guy some ideas and hopes but all he will be doing is spinning his wheels without getting anywhere.
How do you know he doesn't have anything else except for BSA or is able to get something else? And if he does, it will be much easier to help since your (and others') input will most likely correlate well with the equipment's performance. Have you ever shot a perfect square drill with a 7mm using BSA scope? I didn't think so.
 
Thumper, sorry for being so straight forward or "rude" but the truth needs to be told. Leave that BSA on your .22 and choose something else for the 7mm. We are talking about magnum here. Do the best you can on the glass, you will be much, much happier in the long run. I have been down that road, as many others, and all I did was wasted expensive ammo and precious time. You might be OK at 100 yards but will you be happy at that...?
 
Also, do you know the difference between FFP and SFP? Again, for what you want it for, this scope will not perform. Seems to me you need to do a lot more research and hands-on practice with a true 10 power mildot scope first before you worry about ranging different targets with variable power scope, on different magnification settings, and at different ranges. Sounds difficult? It is. It is especially frustrating without the concept of what is what. Did you even find the most accurate round for your rig?
 
Cheers my friend Big Grin


Edited by VYD - October/22/2010 at 15:57
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/22/2010 at 17:50
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Originally posted by thumper5384 thumper5384 wrote:


I'm not wanting to use the scope as a range/size finder.  I have a rangefinder for that. I'm wanting to use it for my known bullet drop at a known distance so all I really want is a distance between the dots at the known range.

Thanks for all of the help, I really appreciate it.

I have no Idea if the BSA will hold up, but the original poster did say he is only interested in using the mil dots as a bdc not ranging. With that said, if I were the OP I would set up a board with 1/4 in grids and make a log at the power ranges you will be using. For hunting I would def know like the back of my hand for 6 x the rest I would leave for the range. At 6 x I am fine for hunting at the ranges I hunt. If anything 6 x at the low end is a little high. But that is me. K.I.S.S.    Keep It Simple (because I am) Stupid lol.

I guess some are just trying to tell you the retical choice you have is not the best choice for hold overs because it does change as the power changes. Mathematically it is feasible to use that way, just not to really practical. 

Anyway if you have the BSA mil dot target it looks like it is set to 10 x as the true mil setting. See below. Other powered BSA scopes also reference the 10x power as being the setting. They also reference a chart. Try contacting BSA and see if you can get a copy of that chart.

Best of luck on your endeavor. 

From a web site:

The Mil-Dot reticle was originally designed to give marine snipers a better range of distances. A mil measures 3.6" at 100 yards or 36" at 1000 yards (at 10x). for long range distance shooting we can say that one mil equals one yard at 1000 yards. In the reticle, one mil is the distance from the center of one dot to the center of the next. The chart shows width equivalents at different distances between the Mil and the MOA.

Clean new design and thoughtful innovations make BSA Optics Mil Dot 6-24x40mm Target Riflescope 1/8 MOA MD624X40 a tremendous buy for the experienced shooter, as well as the novice who wants to get into varmint or target shooting or even long range hunting. The combination of many features alone, make BSA Optics 6-24 x 40mm Mil-Dot Target Rifle Scope 1/8 MOA MD624X40 a best seller, not counting their appearance and sharpness of their lenses.

Application for BSA Optics 6-24x 40 mm Mil-Dot Riflescopes 1/8 MOA MD624X40: Long Range Hunting and Target Shooting with Centerfire and Rimfire Rifles.

Objective and Ocular of BSA Mil-Dot Scope MD624X40 are multicoated for glare reduction and increased brightness. All BSA Optics Mil Dot Riflescopes are waterproof, fogproof, shockproof and carry a limited lifetime warranty. 



Edited by 308 Sav - October/22/2010 at 17:54
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/24/2010 at 13:55
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Here's a copy of a post I made for another forum :
 
There's been alot of traffic lately about folks buying a new scope .
Years ago there was only a hand full of scopes out there to buy. In basically 4 categories 1(1) long range target/varmint 400-1000 yrds (2) High powered rifle low/midrange variable 0-400 yrds  (3) High powered fixed low range 0-100 yrds (4) .22 rim (squirrel rifle). Today the choices are bewildering to say the least ! There's scopes for everything !
  What got me to write this thread is the amount of reticles out there. Wow everybody's got there idea of the perfect reticle . I think it's more a sales hype than anything and some have dumbed down the use of bullet drop with there BCD circles and arrows brackets ect.ect.
  At close range for deer you'll be hard pressed to beat a duplex reticle. With it's wide posts and thin cross hairs.  It's easy to see in low light and still gives you pin point aim out a 100 + yrds .
  Years ago the mil-dot (milliradian not military) dots were not favored by hunters other than vets who used them in service . The thin hairs in the scope were were hard to see in low light and lets face it they can over whelm even the most savvy math folks if you get into the full use of the millemes circle !!

 Here's the basic use of the mil-dot retical That should get you out to 500 yrds range finding on the fly .
Bullet drop and wind drift tables can easley be found on the computer for about any round . That with a mil-dot you'll be deadly !! :p
The basic Mil-dot scope is set at 10X @ 100 yrds. If your buying a mil-dot scope check to see if it's a true mil-dot and at what power the mill setting is . Or just someone's hype .
All Mil-dots should be read with 100 yrds being the base !  5 mils at 100 yrds is 18 " and so on ..

MOA -Inches at 100yds Mils - Increments center to center
A 36 inches 10 increments
B 18 inches 5 increments
C 3.6 inches 1 increment
D Scope Dependent
E 0.75 inches 1 Dot
F Scope Dependent
Chest height distance Mil-dots for deer
5 dots= 100 yds to deer= Distance B in the pic
2.5 =200 yds or 1/2 of Distance B in the pic
1.66= 300 yds  1 and 2/3 of C in the pic
1.25= 400 yds  1 and 1/4 of C
1 500 =yds  = C
Now remember if the height of a deers chest is 18" then with
1 Mil Increments
100 yds - 3.6" x 5 mills = 18"
200 yds - 7.2" x 2.5 mills = 18"
300 yds -12"  x 1.66 mills = 19.92 (close enough) !!
400 yds - 14.4" x 1.25 mills= 18"
500 yds - 18"  You get the idea by now I hope !
KISS -( Keep It Simple Stupid)... The idea is to read distance by simply looking thru your scope while aiming. No complicated calculations... Just look and know the distance. Explaining how it works makes it seem more complicated than it is, so please bear with me as we go thru the numbers.
  Look at the "C" dimension in the chart and on the reticle above. 1 Mil at 100 yards is 3.6 inches or 1/10th of what it is at 1,000 yards (1/10th of 36 inches). At 200, 300, 400, etc... it is 2/10, 3/10, 4/10, etc. So, if you know the size in inches of a target, you can tell how far it is by the number of mildot increments it spans in your scope.
  Looking through the scope at a target 100 yards away, the distance between centers of two mil dots is 3.6 inches. If you figure the chest of a deer or antelope to be 18 inches high, at 100 yards the number of Mil dots it spans is 18 ÷ 3.6 = 5 Mil Dots. So, if you look at a deer through the scope and the chest spans 5 Mil Dots, that deer is 100 yards away. If the chest spans 2.5 Mil Dots, then the deer is 200 yards away... and so forth. See the charts above . You should make your own chart for the dimensions of your target. This is the easiest way to estimate distances with Mil dots.
Hope this helps .
Enjoy and now go make exit holes !
Bill
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/24/2010 at 19:42
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I think the op is using a rangefinder and not interested in ranging. The op is interested in the relationship between hold over at the hash marks at some given magnification vs. the trajectory of his round. There is no math correlation and the op will have to determine the poi empirically.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/24/2010 at 20:20
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wjpr, there's some good info in your post (and welcome to the O.T). I just want to point out that not all deer or antelope are created equal. While the average chest height for deer may be 18" that's an average. If someone assumes 18" and the chest height is actually 17", then a 1 mil range would be off by 28 yards (472 yards instead of 500 yards). A typical hunting round would likely be 7-10" high at that close distance because drops become so drastic at long range. Combine that with wind and the shooter would be lucky to pull off a humane shot.

Speaking from personal experience, ranging with a reticle out to 400 yards can be useful. If you memorize your drops from 100-400 yards (and they won't vary much with altitude or temperature, esp. if you zero at an altitude and temp. near average for your shooting), you can dial in a fairly precise shot on a deer. But I've also found that at that distance you would typically have time for a rangefinder anyway.
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