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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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.
wonder if CBS will puti Sharl Atkinson on this story.
Note Katie Pavlich got CPAC bogger of thr year for her work.
Mucho kudos to Robert here @ TTAG
and Mike Vanderboer @ SipseyStreet.
WANT. Can I get it in CA?
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.
Or does anyone have a ballistics calculator or know of a good one online that might help?
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.
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.
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