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February 17th, 2015
 Horizontal Wind-Drift vs. Distance
OK, here’s a challenge question for you.
Let’s see if you get it right.
Q: If the wind is blowing 10 mph from 9 o’clock and if my horizontal wind deflection is 0.7 inches at 100 yards, what is the horizontal drift at 1000 yards?
You may be thinking, “Well, since the target is ten times more distant, the wind-drift should be around 7 inches, maybe a little more since the bullet will be slowing down.” That sounds reasonable, right?
WRONG.
As you move from near to far, the increase in lateral deflection (from a 90° crosswind) is (roughly speaking) a function of the square of the multiple of distance. If your target is two times farther away, you use the square of two, namely four. If your target is five times farther away, you use the square of five, or twenty-five. In this example, the increased wind drift (from 100 to 1000 yards) is at least 0.7″ times (10 X 10) — over 70 inches (give or take a few inches depending on bullet type). We call that the Rule of the Square. This Rule lets you make a quick approximation of the windage correction needed at any yardage.
Precision Shooting and the Rule of the Square
I was going through some back issues of Precision Shooting Magazine and found many references to the Rule of the Square. This made me curious — I wondered how well the Rule really stacked up against modern ballistics programs. Accordingly, I ran some examples through the JBM Ballistics Trajectory Calculator, one of the best web-based ballistics programs. To my surprise, the Rule of the Square does a pretty good job of describing things.
EXAMPLE ONE — .308 Win (100 to 400 Yards)
For a 168gr Sierra MK (.308), leaving the muzzle at 2700 fps, the JBM-predicted values* are as follows, with a 10 mph, 9 o’clock crosswind (at sea level, 65° F, Litz G7 BC):
Drift at 100: 0.8 MOA (0.8″)
Drift at 200: 1.6 MOA (3.3″)
Drift at 400: 3.4 MOA (14.4″)
Here you can see how the Rule of the Square works. The rule says our drift at 200 yards should be about FOUR times the drift at 100. It the example above, 0.8″ times 4 is 3.2″, pretty darn close to the JBM prediction of 3.3″. Quoting Precision Shooting: “Note that the deflections at 100 yards are typically a quarter of those at 200; lateral deflections increase as the square of the range”. Precision Shooting, June 2000, p. 16.
EXAMPLE TWO — .284 Win (100 to 1000 Yards)
For a .284 Win load, with the slippery Berger 180gr Target Hybrids, the Rule of the Square still works. Here we’ll input a 2750 fps velocity, Litz G7 BC, 10 mph, 9 o’clock crosswind, (same 65° temp at sea level). With these variables, JBM predicts:
Drift at 100: 0.5 MOA (0.5″)
Drift at 500: 2.5 MOA (13.3″)
Drift at 1000: 5.9 MOA (61.3″)
Again, even with a higher BC bullet, at 1000 yards we end up with something reasonably close to the 100-yard deflection (i.e. 0.5″) multiplied by (10×10), i.e. 50 inches. The Rule of the Square alerts you to the fact that the effects of crosswinds are MUCH greater at very long range. In this example, our JBM-calculated drift at 1000 is 61.3″ — that’s over 100 times the 100-yard lateral drift, even though the distance has only increased 10 times.
Note that, even with a 5 mph 90° sidewind, the “Rule of the Square” still applies. The 1000-yard lateral deflection in inches is still over 100 times the lateral deflection at 100 yards.
Why This All Matters (Even in the Age of Smartphones)
 Now, some would say, “Why Should I Care About the Rule of the Square? My iPhone has a Ballistics App that does all my thinking for me”. Fair enough, but knowledge of this basic Rule of the Square enables a shooter to make an informed guess about necessary windage even without a come-up sheet, as long as he knows the distance AND can fire a sighter at 100 or 200 yards as a baseline.
For example, if I see empirically that I need 1″ windage correction at 100 yards, then I know that at 600 yards I need at least roughly (6 x 6 x 1″) or 36 total inches of drift correction, or 6 MOA. (To be precise, 1 MOA = 1.047″ at 100 yards). I can figure that out instantly, even without a ballistics chart, and even if my Smartphone’s battery is dead.
*Values shown are as displayed on the JBM-figured trajectory tables. The numbers can be slightly imprecise because JBM rounds off to one decimal place for both inches and MOA.
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November 17th, 2014
Sierra Bullets has released Version 7 of its respected Infinity Exterior Ballistics software, available now for $39.95 for Windows computers. Renowned Sierra Ballistic Consultants Ted Almgren and Dr. Bill McDonald, who have written all Sierra Software since 1970, also wrote Infinity Version 7. Both are retired scientists from a major aerospace company. Infinity Exterior Ballistics Software version 7 is a sophisticated solver that can output multiple trajectory charts. A built-in database includes bullets and cartridges offered by 15 manufacturers, both U.S. and foreign.
This 13-minute Video Demonstrates the Many Features of Infinity 7 Ballistics Software:
This sophisticated program computes the effects on the bullet trajectory of variations in firing conditions. For example, you can change altitude of the firing point, target angle (uphill/downhill), wind speeds, or even modify the Ballistic Coefficient. In fact, you can change any inputted firing condition or combination of conditions.
One very handy function is the “back-to-zero” calculation. Infinity 7 software will compute where your gun is zeroed if you know that it shoots high by a measured amount at a known range.
Compare Trajectories with Five Different Bullets
One very powerful feature of Infinity 7 is its trajectory comparison capability. With most ballistics programs (such as the JBM online ballistics calculator), you can only view one bullet’s trajectory (and associated drop chart) at a time. Not so with Infinity 7. This software handles up to five different bullets at a time. You can compare downrange velocity, energy, drop, bullet path height, or crosswind drift with results shown in bolt tabular and graphical format. That helps you select the best bullet for your gun and application. The ability to compare downrange ballistics of five different bullets at once is particularly helpful for hunters, who can compare the “hitting power” of different projectiles at various distances.
You can purchase Infinity 7 Ballistics Software as a standalone product for $39.99, or you can buy the Infinity 7 Suite for $59.95, which includes the Sierra Bullets 5th Edition Reloading Manual on CD-ROM. If you prefer a printed loading Manual, a combo pack with Infinity 7 software CD-ROM plus published (hard-back) Reloading Manual is offered for $64.95.
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November 6th, 2014
 In response to questions from a fellow F-Class shooter, German Salazar offered some expert advice in an article entitled: Basics: A Few Wind Reading Tips. Here are highlights from that essay. You can read the entire article on German’s Rifleman’s Journal Website. German cautions that: “I certainly am not attempting to make this short item into a comprehensive lesson in wind reading, but there may be a nugget or two in here for the newer shooter. There is, however, no substitute for range time and coaching.”
Preliminary Matters — Holding Off vs. Knob-Turning
Let’s begin by eliminating one topic altogether — I realize that the predominant method of wind correction in F-Class is holding-off with the crosshairs of your scope rather than adjusting the windage knob. I am a firm believer in aiming at the center and turning the knob as needed, but we’ll leave that for another time and focus on seeing what the wind is doing.
The Wave — Wind Cycles and Shot Timing
I find that most shooters begin to shoot immediately when the time commences rather than waiting for an appropriate moment in the cycle, this often leads to lost points early on. If you’ve been scoring prior to shooting, hopefully you’ve observing the flags and your shooter’s shot placement. It’s a very useful way of gaining some insight into the day’s wind patterns before shooting.
 My technique is based on the understanding of wind as a cyclical wave motion. That statement alone should give you plenty to think about[.] Imagine for a moment, a surfer. He waits for a gentle swell, gets moving on it and rides it through it’s growth and ultimately its crescendo and hopefully avoids being swallowed in its crash. Wind typically behaves in the same fashion as that wave and a smart shooter behaves as does the surfer — get on early in the wave, ride through the major change and get off at the right moment. Knowing when to stop shooting is every bit as important as shooting quickly through the predictable portion of the wave; getting back on to the next wave is a matter of delicate judgment and timing.
When you are on that rising (or falling) wave, the idea is to shoot very quickly to minimize the amount of change between shots and to make a small adjustment on each shot. Too many shooters waste time trying to analyze the exact amount of the change, by which time it has changed even more! Get on with it, click or hold over a set amount and fire the next shot quickly. This is the foundation of how I shoot and it is very effective as long as you know when to start, when to stop and you have a good man working the target – a slow marker is the death of this method.
Watch Shots from Other Shooters
We all watch the wind flags, of course, and the trees if your range is so blessed (ours are fairly barren), and many other small wind indicators. Watching the shots of your fellow shooter can also be a very useful tool and should be observed whenever possible. When a good shooter next to you comes up with a poor shot, it should signal you to stop and reassess conditions as they may not be what they appear.
While scoring for another shooter, take a moment to scan the line of targets. You’ll be surprised at how most of the shot markers move in unison to one side and then the other. The sad truth is that most shooters are behind the changes in the wind and they will get carried to either side of the bull as the wind changes. You’ll see this in the targets as they come up, and once learned, you’ll find that the line of targets is as useful as another row of flags.
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October 19th, 2014
 One of our readers asked “What effect does altitude have on the flight of a bullet?” The simplistic answer is that, at higher altitudes, the air is thinner (lower density), so there is less drag on the bullet. This means that the amount of bullet drop is less at any given flight distance from the muzzle. Since the force of gravity is essentially constant on the earth’s surface (for practical purposes), the bullet’s downward acceleration doesn’t change, but a bullet launched at a higher altitude is able to fly slightly farther (in the thinner air) for every increment of downward movement. Effectively, the bullet behaves as if it has a higher ballistic coefficient.
Forum member Milanuk explains that the key factor is not altitude, but rather air pressure. Milanuk writes:
“In basic terms, as your altitude increases, the density of the air the bullet must travel through decreases, thereby reducing the drag on the bullet. Generally, the higher the altitude, the less the bullet will drop. For example, I shoot at a couple ranges here in the Pacific Northwest. Both are at 1000′ ASL or less. I’ll need about 29-30 MOA to get from 100 yard to 1000 yards with a Berger 155gr VLD @ 2960fps. By contrast, in Raton, NM, located at 6600′ ASL, I’ll only need about 24-25 MOA to do the same. That’s a significant difference.
Note that it is the barometric pressure that really matters, not simply the nominal altitude. The barometric pressure will indicate the reduced pressure from a higher altitude, but it will also show you the pressure changes as a front moves in, etc. which can play havoc w/ your calculated come-ups. Most altimeters are simply barometers that read in feet instead of inches of mercury.”
As Milanuk states, it is NOT altitude per se, but the LOCAL barometric pressure (sometimes called “station pressure”) that is key. The two atmospheric conditions that most effect bullet flight are air temperature, and barometric pressure. Normally, humidity has a negligible effect.
It’s important to remember that the barometric pressure reported on the radio (or internet) may be stated as a sea level equivalency. So in Denver (at 6,000 feet amsl), if the local pressure is 24″, the radio will report the barometric pressure to be 30″. If you do high altitude shooting at long range, bring along a Kestral, or remember to mentally correct the radio station’s pressure, by 1″ per 1,000 feet.”
You can do your own experimental calculations using JBM Online Ballistics (free to use). Here is an extreme example, with two printouts (generated with Point Blank software), one showing bullet trajectory at sea level (0′ altitude) and one at 20,000 feet. For demonstration sake, we assigned a low 0.2 BC to the bullet, with a velocity of 3000 fps.
Trajectory of Bullet fired at Sea Level
Trajectory of Bullet fired at 20,000 feet
if you want to learn more about all aspects of External Ballistics, ExteriorBallistics.com provides a variety of useful resources. In particular, on that site, Section 3.1 of the Sierra Manual is reprinted, covering Effects of Altitude and Atmospheric Pressure on bullet flight.
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October 2nd, 2014
When does a scope cost as much as a new Harley-Davidson? When it is a top-of-the-line 72mm Hensoldt (by Zeiss). The remarkable Hensoldt ZF 6-24x72mm SAM scope integrates ultra-bright apochromatic fluorite glass with a calculator module that provides ballistic info and weather data to the shooter. This 6-24x72mm SAM Hensoldt may be the most advanced riflescope on the planet. With a street price of $11,982.00, it is certainly one of the most expensive. Take a 360° tour with this cool video from Hensoldt Zeiss.
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Hensoldt ZF 6-24x72mm SAM
SAM stands for “Sniper Auxiliary Module”. An integrated ballistics calculator can be programmed for up to four different types of ammo. Sensors in the integrated ring mount measure weather parameters. These values, as well as scope data, are then directly projected into the visual field of the eyepiece. This provides selectable displays of elevation clicks, windage clicks, angle of fire, cant angle, temperature, and air pressure.
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October 1st, 2014
Accuracy 1st Development Group, a training operation based in Texas, will soon release a new instructional video: Long Range Made Easy. This training video features Bryan Litz, author of Applied Ballistics for Long Range Shooting. Many of the shooters shown in the video use the new ABM ammo developed by Bryan’s Applied Ballistics lab for Berger Bullets. Check out the preview “trailer” for Long Range Made Easy.
Watch Trailer for “Long Range Made Easy”
Accuracy 1st Scope Levels
Accuracy 1st also sells some interesting products for precision rifle shooters. Check out this unique, curved-vial scope leveler ring. More precise and sensitive than other scope levels, the Accuracy 1st leveling device can detect 1° of cant. Displayed line increments represent 2.5° of cant.
You may wonder: “Why are these scope levels better than other similar products?” Accuracy 1st explains: “Our levels are of the highest quality and accuracy. Some scope level manufacturers use plastic housings, air bubbles and sub-par glass in their vials. In lieu of a straight bubble vial, Accuracy 1st utilizes a custom curved vial featuring medical-grade glass and a ceramic ball. The use of the ceramic ball eliminates the inherent flaws associated with air bubble levels, which at higher temperatures and pressure will compromise the bubble size causing level inaccuracies. Typically air bubble levels require 3° to 5° [tilt] to even register movement. By contrast, the Accuracy 1st custom level will read movement at a minimum of 1° and will extend measurements out to +/- 10°.”
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September 26th, 2014
If you haven’t visited the Norma website recently, you should click over to www.norma.cc/en/ (the ‘en’ is for English version). There you will find Norma’s “Ammo Academy”, a technical resource that provides information on: Ballistics, Powder Storage, Barrel Wear, and Bullet Expansion. In addition, the Ammo Academy now links to Norma’s Reloading Data Center, where you’ll find loads for nearly 70 cartridge types including: .223 Rem, .22-250, 6mmBR Norma, 6XC, 260 Rem, 6.5-284, 6.5×55, 7mm-08, .270 Win, .284 Win, .308 Win, .30-06, 300 Win Mag, .338 Lapua Mag and dozens more.
The Ammo Academy’s Ballistics section contains some fascinating technical facts:
- After the trigger is pulled, it takes around 0.005 seconds before the firing pin reaches the primer.
- From the firing of the primer it takes 0.0015-0.002 seconds until the bullet exits the muzzle.
- When the bullet leaves the muzzle, the hot gases surround and overtake the bullet, continuing the acceleration for a few centimeters.
- Because the barrel is always angled slightly upwards, the bullet’s flight starts about 3-5 cm below the line of sight.
Norma also offers some good advice about Powder and Cartridge Storage:
To maintain the product quality for as long as possible, you have to keep the powder in a suitable place under suitable conditions. Where possible, store the powder at a constant temperature, ideally between 12 and 15°C (54°F to 59°F), and a relative humidity of 40–50%. If the air is too dry, it will dry out the powder, which will cause the pressure to be higher, thus affecting performance. Also make sure that you close the powder container properly afterwards. Cartridges should be stored under the same ambient conditions to maintain their quality.
For more info on Norma products, CLICK HERE to access Norma’s Catalog Download Page.
Story Tip by EdLongrange. We welcome submissions from our readers.
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August 9th, 2014
Most of us can figure out how to zero our rifles at 100 yards. But do you know how to get a solid zero at long range — as far as 1000 yards? You need to know your ballistics, otherwise you may waste a lot of ammo “sprayin’ and prayin'”. You definitely need to know your exact muzzle velocity, within a few FPS. This is not as simple as it seems, because it is not uncommon for chronograph results to be off by 10 to 20 fps or more, just through calibration error. Accordingly, you may want to test with a pair of chronos and record the results from each (you may be surprised at the variances).
 Video Illustrates Zeroing Process
The process of zeroing rifles for long range is covered in a new “Firearm Science” video from the NRA. This video features George Reinas, a popular competitor on the Top Shot TV Show. George demonstrates how to adjust his scope to compensate for bullet drop at long range. Our friend Dennis Santiago was involved in the making of this video, which was filmed at the Burbank Rifle & Revolver Club in Southern California. The video is narrated by the talented Jessie Duff, one of America’s best action shooters.
 When zeroing at long range, you should first consult a good ballistics program. Select your baseline zero distance (such as 100 yards), then plug in the MV along with salient environmental factors: Altitude, Air Pressure, Temperature, Humidity. After you enter bullet BC, your ballistics program will calculate the drop to the target, expressed in MOA or Mils. Some programs will actually list the number of clicks up from your current zero.
You can print out the data from your ballistics solver as a “drop chart” that can be attached to your rifle stock. If you shoot at various altitudes you may need multiple drop charts.
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July 22nd, 2014
 Carl Zeiss Sports Optics (Zeiss) has a new mobile Ballistics Calculator App for iOS (Apple) and Android devices. Modeled after the web-based Zeiss Ballistics Calulator, the new Mobile App is tailored to work precisely with Zeiss Ballistic reticles. Mike Jensen of Carl Zeiss Sports Optics explained: “We wanted those who use our proprietary ballistic reticles to have a ballistic tool that could be used virtually anywhere you have a signal for your device.”
The Zeiss Ballistic Calculator App allows users to pick their ballistic reticle from a drop-down menu. The user also has the ability to select factory or hand load data as well as environmental variables, and then the system will calculate and display the optimum magnification setting. With this system, distant yardages now coincide with the Zeiss ballistic reticle subtensions. The system allows the user to adjust standard settings for altitude and temperature, as well as other advanced settings, e.g. for muzzle velocity and sight height above bore.
Zeiss Ballistics Calculator App Features:
– One page screen application for fast data entry and easy to read results.
– Comprehensive and current database for factory and hand-loaded ammunition.
– Adjustable settings to customize unique shooting environments.
– Slide feature to visualize how magnification change alters point of impact.
The Zeiss Mobile Ballistic Calculator App can be downloaded at Google Play (Android App) and iTunes (iPhone App) for $4.99. Zeiss has noted that the App will soon be updated to include the Zeiss ASV ballistic turret system.
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June 26th, 2014
 Applied Ballistics, LLC is offering an all-new book by Bryan Litz, the first in a series. The new 339-page, hard-cover book, Modern Advancements for Long Range Shooting, Volume I, documents the ongoing R & D being done at the Applied Ballistics laboratory, the “Area 51″ of the shooting world.
“This new series is heavily based in experimental ballistics, and takes a ‘Myth Busters’-type approach to many of the questions and problems faced by modern long range shooters,” stated Litz. Volume I of the series is scheduled for release in late July, 2014. The book will cost $39.95, but you can pre-order now for $35.95, a 10% savings.
Bryan adds: “Anyone interested in the underlying science behind shooting can benefit from this book. We address the important questions… How much does faster twist affect MV? How does stability affect BC from the muzzle and downrange? What chronographs are capable of high accuracy and precision? What characteristics should you look for in your long range rifle and optic set up? What new gadgets are being developed to enhance long range shooting?
New Book Features Extensive Live-Fire Test Results
Bryan tells us: “The book spotlights state-of-the-art technologies (and methodologies) in long range shooting. New equipment and old ideas are explored using experimental, live-fire testing. Extensive test results are reported in an easy-to-understand way. Among other things, our tests explore the effects of twist rate on muzzle velocity, BC (supersonic and transonic), precision, even spin rate decay for various rifling profiles as they are tested experimentally.
Chronographs and Optics Are Tested and Compared
Litz’s new book traces the evolution of modern rifle, bullet, and optic design. Results from chronograph comparison tests are presented, showing the strengths and weaknesses of available commercial chronographs. High-tech instrumentation such as laser rangefinders and wind measurement devices are explained in detail by contributing author Nick Vitalbo.
The New Book Puts Theory into Practice
We asked Bryan Litz how this new book differs from his previous treatises. Bryan replied: “My original Applied Ballistics for Long-Range Shooting book explains the fundamental elements of external ballistics. It’s the academic background which all future work relies on. The new book, Modern Advancements in Long Range Shooting, covers the ongoing development of equipment and ideas. We explore things like twist rate effects, modern rifle and optic design, and some of the high tech instruments which are being used to enhance the effectiveness of long range shooting.
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June 9th, 2014
 Ballistics books have gone digital. Bryan Litz’s Applied Ballistics For Long-Range Shooting (2nd Edition), the leading treatise on the subject, is now available in digital eBook format. This new eBook version contains all the text of the print version, all the charts, all the diagrams, and all the photos. You get all this in an easy-to-read, easy-to-search format that can be viewed on a variety of devices*. You can access the book on your home computer, on your laptop, on a tablet, on a smartphone, or on a lightweight, portable Kindle e-Reader. And yes, iPad users can use the Kindle app to read the book on an iPad.
CLICK for FREE Sample of Applied Ballistics
for Long-Range Shooting (2d Ed.) eBook
NOTE: After clicking this link to go to Amazon.com, click on the blue book image labeled “Look Inside”. This will launch a preview window. Alternatively, Kindle users can click the “Send Sample Now” button.
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Advantages of the eBook Edition
The eBook release of Bryan Litz’s most popular and comprehensive ballistics book is a big deal, in our opinion. There are many advantages to the digital format. First you can quickly search for any term or reference, or click from table of content entries to desired chapters. Second, you can highlight text and bookmark pages for future review. Third, you can easily change the font size to enhance reading for older eyes. Fourth, you can zoom in the charts, diagrams, and photos for a better view. Last but not least, you can easily carry the entire text in the field on the same digital device that holds your ballistics solver software.
The new eBook version of Applied Ballistics for Long-Range Shooting (2d. Ed.) is available now on Amazon.com for $39.95. |
Highlights of eBook Edition
The eBook version of Applied Ballistics for Long-Range Shooting (2d Ed.) is available now on Amazon.com. Since its release in 2011, the second edition (hardcopy) of Applied Ballistics for Long Range Shooting has sold over 10,000 copies. It’s the modern ‘go to’ book on the subject of ballistics for long range shooters. The Second Edition of the book includes two additional chapters covering extended long-range shooting and monolithic bullets.
200 Bullet Types Tested. In this eBook edition, Bryan Litz includes data from his own personal field tests with over 200 bullet types. Performance data (G1 and G7 BCs confirmed by live-fire testing) is presented along with 2-D drawings for hundreds of long range bullets.
Ballistic Program Included. eBook buyers can receive the Point Mass Ballistics Solver 2.0 for no extra charge. The software comes on a CD with the hardcopy. With the eBook, there are two ways to access the ballistics program. First, you can access the free AB online ballistics solver through embedded links in the eBook and run directly from your eReader. Alternatively, you can request the PM Solver program to be emailed to you for running on a PC.
“Our mission at Applied Ballistics is to be the complete and unbiased source of external ballistics information for long range shooters,” stated Bryan Litz, author and owner of Applied Ballistics, LLC. “We’re constantly testing new claims, products and ideas and dispensing the marketing hype which can make it difficult for shooters to master the challenging discipline of long range shooting. We developed the original hard copy of the book in order to provide shooters of all capabilities with this knowledge. The release of the eBook will not only provide readers with the same knowledge, but do so in a more accessible and mobile way.”
Sample Page from eBook
* Installation of FREE eReader software may be required for viewing on desktop computers, laptops, tablets, and smartphones. This only takes a minute or so.
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June 5th, 2014
The new-for-2014 Caldwell Crosswind Professional Wind Meter does much more than measure wind velocity. Along with Current Wind Speed, this device will measure and display: Average Wind Speed, Max Wind Gust, Temperature, Station Pressure, Barometric Pressure, Altitude, Density Altitude and even Wind Chill factor. Select among mph, ft/min, km/h, m/s, or knots for the wind speed units.
The swiveling impeller head (set parallel to barrel) allows you to determine an interpolated 90° crosswind value to use in your ballistics calculations. This eliminates a lot of guesswork.
You might say, “Why do I need a rotating head, I can just turn the whole wind meter to align the impeller axis with the wind?” Yes you can, but then you merely get a raw speed value, and you have to guesstimate the wind angle, and then calculate your actual windage correction based on the vector.
The rotating impeller ring on the Caldwell simplifies the job of calculating windage. The swivel head is designed to show an effective 90-degree crosswind value, no matter what the actual wind direction. Here’s how it works. Hold the unit with the display screen facing you. Then rotate the impeller head until it aligns with the barrel axis (bullet line of flight). The plastic shell surrounding the impeller is specifically designed so that the blades will spin faster or slower depending on the true wind angle. This allows the unit to estimate the effective 90-degree crosswind value (for your ballistics program). Pretty clever eh? See diagram to understand how this works:
This unit comes complete with rotating anemometer head, protective holster case, and one CR2032 battery. The unit has an auto “Power-Off” feature to preserve battery life. There is also a “Data Hold” function plus an LCD Backlight. NOTE: When figuring effective 90° crosswind values, Caldwell recommends using Average Wind Speed mode rather than Current Wind Speed.
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