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Mil Dot question...

Discussion in 'Rifle Country' started by jon8777, Sep 5, 2009.

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  1. jon8777

    jon8777 Member

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    Readin up on Mil Dot scopes... and heres my question and stop me where I go wrong.... and tell me If I am right.....

    1 mil = 36" (aprox) target height at 1000y

    Then at 100y 1 mil = 3.6"

    Then at 200y 1 mill = 7.2" and so on..

    So heres my question (trajectories are fake for ease)...

    If my gun was zero'd for 100y and at 300y my bal table told me I was 10.8" low I would hold 1 mil dot high (3.6" x 3 = 10.8") to hit dead on.

    Then at 500y I was 36" low from the bal chart I would hold the 2nd mil dot (3.6 x 5 = 18", 18"/36" = 2) correct?
     
  2. sscoyote

    sscoyote Member

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    That's correct. But the "even" #'s are easy. If u're 49" low at 625 yds, then that's 7.84 inch per hundred yds. (IPHY) 49/6.25. So divide by 3.6 IPHY and u get 2.2 mil dots down. (The bottom of the dot is .1 mil lower than the center of the dot, so u have to interpolate the next .1 mil). Fortunately u don't have to do this most of the time since there r a bunch of ballistics programs around that have a mil calculator in them.

    The same basic concept is used for ballistic reticles as well. It just requires one more calculation.
     
  3. A-FIXER

    A-FIXER Member

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    yes that what my mil-dot shooting manual manual says got it at SWFA and the price is cheaper than midway.... and it comes with the bal -chart that its self is worth it
     
    Last edited: Sep 6, 2009
  4. jon8777

    jon8777 Member

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    Thanks for the help. I want to stay away rom a BDC trype retical and go with a true mil dot type retical, nothing over the top, but something thats useable.

    Any thoughts on Nikons mil dot scopes?
     
  5. jon8777

    jon8777 Member

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  6. taliv

    taliv Moderator

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    jon, you can certainly do things in yards with mil dots, but if you switch to meters, the math gets SO much easier. calculators are totally unnecessary
     
  7. sscoyote

    sscoyote Member

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    Taliv--how does the metric system make the calculating easier?

    Jon--i have a 6-18x Nikon Buckmasters that i use on an XP-100 handgun in 17 Fireball for shooting prairie dogs. The mil-dot is correctly cald. for 12x in most of the Nikon optics beyond a 3.5-10x. At 18x the subtension becomes 66% of 3.6 @ 2.4 inch per hundred yds. If used for rangefinding the math cahnges a bit but u get more accuracy from the system. With this optic on this rig i use the reticle for windage and turret for elevation.
     
  8. Maverick223

    Maverick223 Member

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    Your calculations appear to be correct...but if you have mil/mil then everything gets much easier real fast (of course using meters as Taliv suggests). MOA/MOA is an improvement but metric is better IMO. :)
     
    Last edited: Sep 6, 2009
  9. sscoyote

    sscoyote Member

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    I can see how some of the rangefinding calcs r a touch easier since u have a base 10 sytem to work with (10 cm to 100 m), but u still have to pull out a calculator to divide whatever your tgt. size is in cm by whatever your mil-reading is (unless you're dealing with a whole # for mil-reading).

    If i needed to range a 10" standing prairie dog or 3.5" wide (i actually measured a couple adults once and they were very close to this measurement) with my system it would be this calc. here for a unit of subtension of 1.8" per hundred yds.--

    for 10"= 555.6/ mil-reading = yds.

    I actually tried ranging several once on a very hot day in an uncomfortable position and was within 25 yds. of lasered on every dog for about 5 or so out to 300-400 yds. (can't remember exactly--long time ago now).
     
  10. sscoyote

    sscoyote Member

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    It is fun attempting 1st-shot connections with a 17 cal. pistol out to 500 yds. in some wind using a reticle matched to ballistic program calcs. It's pretty enlightening how well it can be accomplished though even with the lowly 25 Horn HP (BC-wise, that is).

    Jon--i love the Nikon systems. Here's the reason why. I like mil-dot reticles in second focal plane scopes since u have a lot more flexibility for rangefinding and downrange zeroing. U can use them at the mil-cald. power or u can play with them some to provide a more accurate and finer subtension system. Just look at the catalog--the 4.5-14x is a good example. U can use it at 12x (calibrated) or u can just use it at the optic's highest power (14) where it measures 3.12 IPHY (instead of 3.6). Now just recal the downrange zero reference and/or rangefinding at that power and u're good to go.

    I also like the fact that the Nikon catalog publishes so much info on their reticle subtensions...and it seems to be accurate.

    When i apply reticle for downrange zeroing and rangefinding i calculate and verify/troubleshoot the system then put the dope in a Butler Creek scope cap cover (unless u're going beyond 500-600 yds. or so) in 50-yd. increments--both elevation and windage. Rangefinding goes into a BC Blizzard-style objective cover (u can disassemble it and place a sticker on a piece of thin cardboard and put it all together again). This way when i flip the covers open everything i need is right there at a glance without having to get out of position to see it---my system. I always calc my system for the optic's highest power since it acts as a "zero stop" sort of, and i don't have to look at the power ring to make sure i'm on the right power--i can feel it.
     
    Last edited: Sep 7, 2009
  11. jon8777

    jon8777 Member

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    How well do the turrets on the Buckmater respond to constant change in trajectories? Do they re-zero w/o problems?
     
  12. sscoyote

    sscoyote Member

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    I haven't had any problems with mine.
     
  13. jon8777

    jon8777 Member

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    I have the 6-18 Buckmaster in Nikoplex w/turrets. I have never field adjusted the turrets for a shot. I have always been hesitant about its not re-zeroed for the next shot.

    My buddy has the 4-14 w/Mildot, hes had some great luck (25-06) with the ground hogs this year... so I am looking to swap the 3-9 Nikon on the 223 to the 209x50 and give the 223 a bit more accuracy.

    With the 4-14 having a 12x setting or a calculated 14x mil dot setting, whats your opinion on a 2.5-10 Monarch Mildot?

    Its going to be a 200-400y ground hog gun thats going to see more field action than any rifle I have, so I want a scope thats a no BS dead on w/o breaking the bank.
     
  14. Maverick223

    Maverick223 Member

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    What brand...Hubble? :neener:
     
  15. taliv

    taliv Moderator

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    here's an easy question to illustrate using meters/cm vs yards/inches:
    "How big is a mil at a given distance?"
    (as in... i just ranged a target at x meters or yards, so if i hold over 1 mil, how much distance will it move the impact?)


    easy:
    1 mil @ 100 meters == 10 cm (think: 100/1000 = .1 which is 10cm)
    1 mil @ 100 yrds == 3.6" (think .1 yrds ... uhh... 36" in a yrd so multiply by .1)


    practical, not so easy:
    1 mil @ 167 meters == 16.7 cm (think: just move decimal place to .167m, convert to cm by moving it back 2 places)
    1 mil @ 167 yrds == 6.012" (think... uhh .167 yrds ... 36" in a yard... oh crap, where's my calculator?)


    now granted, if you're like i am, you can visualize 6" easier than 16.7cm, but i find it's easier in the long run to acquaint myself with some reference items in m/cm than it is to do 2x3 digit multiplication on the clock
     
  16. Maverick223

    Maverick223 Member

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    I'll make it easy for you...2.54cm=1in. So given mil/mil (my preference) take the measurement (in inches) and multiply by about 2.5 (for 1/10 mil)...easy metric conversion even in field conditions...I can just shoot in Meters and cm pretty easily. :)
     
  17. jpwilly

    jpwilly Member

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    Here's an easy way to range a target for example 72" tall. (will not work for FFP scopes) Turn your power nob untill the object measures 4.5 mil dots then read power setting and multiply it times 100 for your range.
     
  18. jon8777

    jon8777 Member

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    Taliv-

    Yes meters would be easier... call me a redneck, but I like my feet and inches... We did a few jobs at works a few years back in metric, it drove my nuts trying to convert back and forth...


    Greenhorn Q-... Whats FFP?
     
  19. jpwilly

    jpwilly Member

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    FFP = Front Focal Plane
     
  20. sscoyote

    sscoyote Member

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    There is an advantage to using the mil in metric as long as u're using the reticle at it's cald. power. But for me i use many reticles for rangefinding from simple plex to Ballistic Plex. Besides that IMO there's no better way of understanding the system than working with the most basic form of the mil-ranging formula since it opens up a world of flexibility that's easier to see. Here's the most basic form (inches to yds.)--

    tgt. size (") x range of reticle subtension measurement (usually 100 yds.) / reticle subtension (") / "mil-reading" (decimal equivalent) = range (yds.)

    Example-- 10" tgt. occupies 3.3-1.8 inch per hundred yd. units of subtension--

    10 x 100 / 1.8 / 3.3 = 168 yds.

    Using this form of the "mil-ranging formula" allows the user to easily apply it with any reticle with at least 2 stadia points in it (archery sight pins too), it allows for calculating the accuracy of your reticle-ranging system, "reverse-milling", and it also defines downrange zeroing with any reticle also (bullet drop is the same type of dimension as a tgt. size).

    Jon-- FFP means "first focal plane". The significance relative to Willy's post above is that no matter what power your FFP variable scope is on the stadia to stadia measurements (subtensions) don't change. What he's done is used the inversely proportional relationship of a SFP (second focal plane) system of a variable-powered optic to calculate a rangefinding system--magnification is inversely proportional to reticle subtension.
     
    Last edited: Sep 9, 2009
  21. MCMXI

    MCMXI Member

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    That's an unrealistic example of scope use IMO. If you've ranged a target at X meters or yards, you'd refer to your DOPE to read off the required holdover or come-up for that range. Talking of ranging, here's a more realistic scenario. A target at an unknown distance that you estimate to be 6 ft tall measures right at 1.75 mils in your FFP scope (or SFP on correct magnification). 6' = 2 yards = 1.83m. What's the range to the target?

    (Target Height (units)/mils)*1000 = range (units)

    (2 yards/1.75 mil.rad)*1000 = 1143 yards

    (1.83m/1.75 mil.rad)*1000 = 1045 meters

    This is a more realistic use of a ranging reticle and both would most likely require a calculator. It shows that the Imperial System is no more complicated than the Metric System in terms of ranging.

    However, another common situation is making POA/POI corrections when target shooting. If you have a mil reticle and mil adjustments, and assuming you can use your reticle (or a mil spotting scope) to measure the distance between the POA and the POI, it's easier to dial in the correction. A mil reticle with MOA adjustments requires an extra step (and probably a calculator) to convert mils to MOA by dividing by 0.29089. To convert mils to MOA "on the fly", multiplying mils by 3 will work fairly well out to 300 yards, and by 3.5 out to 600 yards.

    When I'm shooting F-Class targets at 600 yards, if my first sighter is halfway between the 9 and 8 rings at 3 o'clock, I know that I need to come left by 1.25 MOA because I know the X, 10, 9 and 8 rings are 1/2, 1, 2, and 3 MOA respectively. In other words, mil/moa works just fine for F-Class shooting with no calculators required. However, I realize that other disciplines may benefit from mil/mil scopes but I'm not sure what those disciplines are. I would suggest that a mil/moa FFP scope is more useful/practical for most people compared to a SFP mil/mil scope, but that said, I'm seriously considering ordering the NXS 3.5-15x50 F1 with mil/mil adjustments.

    :)
     
    Last edited: Sep 9, 2009
  22. Maverick223

    Maverick223 Member

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    I would look into the Premier Reticles 3-15x...that is about the same price, or perhaps a little less...and has better glass and features IMO (not that NF glass is bad). :)
     
  23. sscoyote

    sscoyote Member

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    I have 3 MD reticles--1 as above, i also have 2 Leupold's. 1 has the TMR, that i love for the .2 mil subtension units as it provides for .02 mil rangefinding accuracy. The other's a 6.5-20x FFP with Darrell Holland's Ultimate Mil Reticle in it. It's on an XP-100 6.5 WSM handgun. 1st shot out of that rig on game was a 435-yd. coyote @ 1.5 mil elevation and 0 windage.
     
  24. MCMXI

    MCMXI Member

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    sscoyote, for the kind of shooting you do, what are your thoughts on FFP vs. SFP scopes?

    :)
     
  25. MCMXI

    MCMXI Member

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    Mav, I know you like the PRH and I'm still waiting on a range report. You've got some magazines now so it should be any day right? :)

    :)
     
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