Ask Foghorn: Meters v. Yards for Zero Distance?

courtesy chemistry.about.com

Jeremy writes:

I don’t know if you guys have gotten this question before, or if it would warrant writing an article, but do you have any feedback on zeroing a rifle on a range measured in yards, and then how accuracy would be affected when shooting that rifle estimating distance based on meters? The difference @ 100m vs. 100 yards is going to be about 9′ so my assumption is that even to the max effective range of a 5.56 round, there isn’t going to be enough of a difference to see a noticeable POI shift. Do you have an opinion?

Good news for the lazy among us: for the typical zero on a 5.56 gun, it doesn’t matter . . .

Meters are longer than yards, but only by a tiny bit. For one meter or ten meters, it doesn’t really matter. In fact, the difference between meters and yards at 50 yards is just about negligible. Which is perfect for our purposes.

The typical 5.56 rifle zero is a 50 yard/meter zero. That puts the round on target at 50 yards and 200 yards, with less than a 3 inch vertical deviation over that distance. It’s also the zero that’s used with Leupold and Trijicon’s optics, as zeroing at 50 yards will align the trajectory with the reticle.

At 50 yards, the difference between meters and yards is still so small that it really doesn’t matter. In fact, the inherent inaccuracy of your barrel and ammunition will probably do more to mess with your zero than the difference between yards and meters (more about that here).

In fact, even at longer distances the difference still really doesn’t matter. Doing the calculations in either metric or imperial units will get you close enough to where you can walk the shot on target with a couple rounds.

If you’re going for precision shooting, though, it might matter. But if you’re the “one shot, one kill” kind of person, you already know your holds (or can calculate them) in either system and adjust as needed.

For new shooters, my advice is not to sweat the small stuff. Even for NRA High Power service rifle matches, I calculated my ballistics in yards while the range at MCB Quantico is laid out in meters and it didn’t slow me down. Two sighters and I was tapping the X ring. The difference between meters and yards is important, and for those who need to make a precise shot, it’s important to understand the difference and adjust as necessary. But for those just starting out, it’s no biggie.

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comments

  1. avatar Brian Bowman says:

    They bid us change the ancient “names,”
    The “seasons” and the “times,”
    And for our measures go abroad
    To strange and distant climes.

    But we’ll abide by things long dear,
    And cling to things of yore,
    For the Anglo-Saxon race shall rule
    The earth from shore to shore.

    Then down with every “metric” scheme
    Taught by the foreign school.
    We’ll worship still our Father’s God!
    And keep our Father’s “rule”!

    A perfect inch, a perfect pint,
    The Anglo’s honest pound,
    Shall hold their place upon the earth,
    Till Time’s last trump shall sound!

    Then swell the chorus heartily,
    Let every Saxon sing:
    “A pint’s a pound the world around,”
    Till all the earth shall ring,

    “A pint’s a pound the world around”
    For rich and poor the same:
    Just measure and a perfect weight
    Called by their ancient name!

    Of course, the scientific nerd in some of us may express a somewhat cumbersome riposte, as follows:

    Replace the inch, we say to thee
    Make each equation neater
    For every scientist in the world
    Will use the same centimeter

    LOL! 😉

  2. Thanks for confirming my assumptions Nick! I had forgotten about this email 🙂

    If I could find a decent range or large enough private property, I’d love to set up one target @ 500m and one @ 500 yards just to see if I could still knock them out in one shot without adjustments.

  3. avatar Jeff says:

    Without commenting on the gist of the article (that the difference is immaterial)…the math is a bit wrong. There are 3.28083 feet per meter, but only 3 feet per yard. 100 yards is 300ft, and 100 meters is 328.083 ft. 100 yards is 91.44 meters. (300 divided by 3.28083). The difference is either 28 ft or about 9 m or yards.

    A single hash as used above by the author implies feet (9′). I think the author mis-wrote the difference is 9 feet when he really meant yards or meters.

    1. avatar Accur81 says:

      Yes. The difference between yards and meters will matter for precision shooters past 300 yards or so, depending upon caliber. But precision shooters already know that, and will adjust their equipment accordingly. Personally, I like feet and yards because they are American measurements.

      Newbies will likely be confused and won’t bother with conversions. Since most ranges are set up in yards, that should be fine.

  4. avatar Cyrano says:

    Now to discuss MOA is not 1 inch at 100 yds but 1.047197580733 inches or 10.47 inches not 10 at 1000 yds. 🙂

  5. avatar Don Curton says:

    Well now, that all depends …

    Are we shooting God-fearing Americans, or filthy Euro-trash? I say hold your fire until you see the whites of their eyes, damn the torpedoes and full speed ahead!!

    Or just sight in at 100 yards like God intended.

  6. avatar Nickbnumbers says:

    That’s a lot of math, fractions, and cancellation marks. You can do it that way, or you can go to google and type in “100 yards to meters.”

    As for real world use, just remember that it’s off by 10% and you should be close enough for most applications.

    If you’re an American who is forced to shoot 300 meters, just know you’re shooting 300+10% or 330 yards. Alternatively, you can pretend 800 yards is 800-80=720 meters. In real life it’s 328 yards or 731.5 meters, but the 10% rule is pretty close for most uses.

    Don’t try this with a 308 at 1000 yards or you’ll miss your elevation by a foot or two. For a 308, use a laser rangefinder. Keep walking toward the target until the laser indicates 600 of something. Then shoot. 🙂

  7. avatar jbarr says:

    Google really can be your friend. Try the search: 100 meters to yards

    Or just enter: unit converter

    and you get a really slick unit conversion tool.

  8. avatar Brandon says:

    Ive heard that m16/ar15 have same POI at 36YDS and 300YDS. I’m assuming that’s with a 62 gr penatrator round I don’t know maybe a 55 gr FMJ. The range I go to has part of it setup for 25 and 50 yds. Then a rifle part that goes 100,200,300 YDS I have a Colt LE6920 with a 1″×7″ twist 16″ barrel I’m trying to figure a poi using these distances that will equal out to about the same poi as the metered version bullet weight isn’t an issue because I reload and can get bullets as heavy as 90gr in the mag I just need to know what speed to run them and what’s my shorter yardage to have same poi around 250 to 300. Hope I made that clear enough. Thank you for any input or ideas.

  9. avatar Brandon says:

    Or does anyone have a ballistics calculator or know of a good one online that might help?

    1. avatar David Walters says:

      The Sierra ballistic calculator (version 7) is the cat’s meow. But you’ll shell out a few bucks for it.

      But just about any ammunition manufacturer will have a decent but basic ballistic calculator on its site.

  10. avatar David Walters says:

    Yards or meter, doesn’t really matter much within 300 yards. But at longer distances with 5.56 it can come into play whether you’re a precision shooter or an average shooter.

    Couple of other points. I’m an ex-Marine (you goofballs who have an epileptic fit on former vs. ex, stuff it) and in my day we used optical ranging devices (like this one http://www.vortexoptics.com/category/solo_rt_monoculars) which had either milradian or mildots reticles for ranging.

    These optics estimate range by the shooter knowing the size of the target in either standard or metric dimensions. But zeroing my rifle at either a standard of metric range is a no brainer as I’ve calculated the elevation offset for each load from ballistic tables if the rifle is zeroed for a metric on a standard range.

    My local range is standard. But I like to zero my weapon at 300 m as that’s what I understand the Marines use today (they must have a good reason, I figure, and if it’s good enough for my brothers today it’s good enough for a old fart like me).

    So, I use elevation offsets if I zero my weapon for 300 m using a 100 yard range (see here: http://i1378.photobucket.com/albums/ah103/longfisher/Wind%20Print%20Images_Page_1_zpsszexw6ix.jpg). Please note the offsets just under the tables, for instance.

    You’ll see on the card that I publish both meters and yards (1 yard =.9145 meters). So, I can inter-convert between the two easily and as needed.

    I also use a circular, pocket slide-rule calculator to estimate accurately the range to an object of known size. Whether I want the result in either yards or meters takes only one more multiplication step on the slide rule which would take about 2 seconds.

    So, essentially, I’m made the use of meters or yards interchangeable. Works for me.

    1. avatar David Walters says:

      For those who us optical ranging devices which are calibrated in either millradians and who want to be able to estimate range to approximate accuracy without using a calculator or sliderule, here’s a table for you based on the English standard measurements (inches, feet, yards, etc.) rather than the metric standard which will bring you pretty darned close. Of course, your target size needs to be known in standard measurements, in this case in inches.

      http://i1378.photobucket.com/albums/ah103/longfisher/MRAD%20vs%20Inches%20Range%20Table_Page_1_zpsuf1rlyxf.jpg

      My wife can’t wield a calculator or slide-rule. So, along with her other dope cards for various load (all in a wrist coach) I inserted the above table. So, if she can measure the milradians either with a scope or monocular to within about 0.2 milradians she can pretty accurately estimate the range.

      Oh, the grey cells are those above about 600 yards where I think my AR-15 won’t be very accurate.

      Longfisher

      Enjoy

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