Each Wednesday, the U.S. Army Marksmanship Unit publishes a reloading “how-to” article on the USAMU Facebook page. This past week’s “Handloading Hump Day” article, the latest in a 7-part series, relates to chronograph testing and statistical samples. We highly recommend you read this article, which offers some important tips that can benefit any hand-loader. Visit the USAMU Facebook page next Wednesday for the next installment.
Chronograph Testing — Set-Up, Sample Sizes, and Velocity Factors
Initial Chronograph Setup
A chronograph is an instrument designed to measure bullet velocity. Typically, the bullet casts a shadow as it passes over two electronic sensors placed a given distance apart. The first screen is the “start” screen, and it triggers an internal, high-speed counter. As the bullet passes the second, or “stop” screen, the counter is stopped. Then, appropriate math of time vs. distance traveled reveals the bullet’s velocity. Most home chronographs use either 2- or 4-foot spacing between sensors. Longer spacing can add some accuracy to the system, but with high-quality chronographs, 4-foot spacing is certainly adequate.
Laboratory chronographs usually have six feet or more between sensors. Depending upon the make and model of ones chronograph, it should come with instructions on how far the “start” screen should be placed from one’s muzzle. Other details include adequate light (indoors or outdoors), light diffusers over the sensors as needed, and protecting the start screen from blast and debris such as shotgun wads, etc. When assembling a sky-screen system, the spacing between sensors must be extremely accurate to allow correct velocity readings.
Statistics: Group Sizes, Distances and Sample Sizes
How many groups should we fire, and how many shots per group? These questions are matters of judgment, to a degree. First, to best assess how ones ammunition will perform in competition, it should be test-fired at the actual distance for which it will be used. [That means] 600-yard or 1000-yard ammo should be tested at 600 and 1000 yards, respectively, if possible. It is possible to work up very accurate ammunition at 100 or 200 yards that does not perform well as ranges increase. Sometimes, a change in powder type can correct this and produce a load that really shines at longer range.
The number of shots fired per group should be realistic for the course of fire. That is, if one will be firing 10-shot strings in competition then final accuracy testing, at least, should involve 10-shot strings. These will reflect the rifles’ true capability. Knowing this will help the shooter better decide in competition whether a shot requires a sight adjustment, or if it merely struck within the normal accuracy radius of his rifle.
How many groups are needed for a valid test? Here, much depends on the precision with which one can gather the accuracy data. If shooting from a machine rest in good weather conditions, two or three 10-shot groups at full distance may be very adequate. If it’s windy, the rifle or ammunition are marginal, or the shooter is not confident in his ability to consistently fire every shot accurately, then a few more groups may give a better picture of the rifle’s true average.
Preliminary Load Development and Velocities
When developing a load for ones firearm, a chronograph is a very useful tool. Naturally, it tells the bullet speed, allowing ballistic calculations for wind deflection and trajectory, as well as velocity variation. It can also be used, in conjunction with recent handloading manuals, as an indirect indicator of pressure.
Differences between individual barrels, chamber throats, and powder lots, plus many other variables, can cause results to differ from those cited in the manuals. Thus, beware the notion of a “magical high-speed barrel.”
When Velocities Raise Pressure Concerns — Suppose the manual states that their 26-inch .260 barrel achieved 2900 fps with X bullet, Y powder, Z case, and W primer. If you achieve that speed with identical components in your 26-inch barrel while using five (5) grains less powder, that should raise a red flag. Pressures may be at or near maximum in your rifle, despite the higher “maximum” charge cited in the manual. Observe for pressure indicators as discussed in your manuals, and never exceed published maximum powder charges.
When working up a potential match load for your rifle, it is wise to survey at least 2-3 current factory sources of data for your powder/bullet combination. This will give you a sense of the variations possible due to random factors. Then, beginning at a safe, listed “starting” powder charge, work your way up in increasing powder increments while shooting over the chronograph. Also, assess your brass and rifle for signs of increasing pressure.
What size powder increments should be used? This depends on the case volume and powder chosen. A 0.3 grain or 0.5 grain increase in powder charge may be significant in a .223, but of little consequence in a .300 Magnum. Faster burning powders are more sensitive to small changes in powder charge, increasing pressures more rapidly than slow-burning powders.
Chronograph Sample Sizes — Factors to Consider
How many shots should one fire to obtain an accurate velocity for each powder charge increment when loading? That depends in part on the uniformity of velocities given by your particular powder/bullet/barrel combination.
For example: a 3- or 5-shot sample gives an extreme spread (ES) of 140 fps between the high and low velocities recorded. The lack of uniformity indicates that firing 1 or 2 shots over the chronograph to check a powder charge is likely to give a wide margin of error. In such a case, larger sample sizes will give a better idea of the true, average velocity. While approaching the loading manual’s listed maximum charge, track the ascending velocities per charge increment. One may well see that as charges approach maximum, velocities may become much more uniform. Moreover, velocity gains per increment of increase often become smaller. Ideally, one won’t encounter velocity variations this large. Changing primers and/or neck tension may increase uniformity. If wide variations persist, however, a different powder may offer great improvement.
Consider this: A 2-shot scan gives double the data of a one-shot sample. A 4-shot sample gives twice the data of a 2-shot scan. Larger samples are particularly useful if there is much velocity variation in the population.
On the other hand, one might already be familiar with a particular powder/bullet combination in one’s barrel. If it is known to have little variation, a 1 or 2-shot scan in the early stages while working up toward the maximum can be useful, while saving expensive bullets. As powder charges approach their maximum, some like to test accuracy while shooting over the chronograph. Although it’s a bit trickier to set up the bench, chronograph and target, this does yield more data per bullets expended. In such an instance, 5-shot or even 10-shot groups may be desirable at times.
Consider 20-Shot Sample for Long-Range Match Loads
Once one arrives at a load combination intended for competition use, one should chronograph at least a 10-shot sample. This gives a reasonable picture both of the load’s uniformity and its average velocity. For long range use, a 20-shot sample of ones finalized match load is even better. This accurately shows the uniformity of one’s velocities over time. It is more likely to reveal any rare shots that develop velocities significantly different from the average.
Thus ends Part 7 in our series on Accuracy Testing and Chronographing. Next week, we’ll conclude our section on Chronograph Testing. Until then, stay safe and enjoy the shooting sports!
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The Coriolis Effect comes into play with extreme long-range shots like this. The rotation of the earth actually moves the target a small distance (in space) during the course of the bullet’s flight. Photo by Dustin Ellermann at Whittington Center Range.
When you’re out at the range, the Earth seems very stable. But it is actually a big sphere zooming through space while spinning around its axis, one complete turn every 24 hours. The rotation of the earth can create problems for extreme long-range shooters. During extended bullet flight times, the rotation of the planet causes an apparent deflection of the bullet path over very long distances. This is the ballistics manifestation of the Coriolis Effect.
Bryan Litz of Applied Ballistics has produced a short video that explains the Coriolis Effect. Bryan notes that Coriolis is “a very subtle effect. People like to make more of it than it is because it seems mysterious.” In most common shooting situations inside 1K, Coriolis is not important. At 1000 yards, the Effect represents less than one click (for most cartridge types). Even well past 1000 yards, in windy conditions, the Coriolis Effect may well be “lost in the noise”. But in very calm conditions, when shooting at extreme ranges, Bryan says you can benefit from adjusting your ballistics solution for Coriolis.
Bryan explains: “The Coriolis Effect… has to do with the spin of the earth. You are basically shooting from one point to another on a rotating sphere, in an inertial reference frame. The consequence of that is that, if the flight time of the bullet gets significantly long, the bullet can have an apparent drift from its intended target. The amount [of apparent drift] is very small — it depends on your latitude and azimuth of fire on the planet.”
Coriolis is a very subtle effect. With typical bullet BCs and velocities, you must get to at least 1000 yards before Coriolis amounts to even one click. Accordingly, Bryan advises: “Coriolis Effect is NOT something to think about on moving targets, it is NOT something to think about in high, uncertain wind environments because there are variables that are dominating your uncertainty picture, and the Coriolis will distract you more than the correction is worth.”
“Where you could think about Coriolis, and have it be a major impact on your hit percentage, is if you are shooting at extended range, at relatively small targets, in low-wind conditions. Where you know your muzzle velocity and BC very well, [and there are] pristine conditions, that’s where you’re going to see Coriolis creep in. You’ll receive more refinement and accuracy in your ballistics solutions if you account for Coriolis on those types of shots. But in most practical long-range shooting situations, Coriolis is NOT important. What IS important is to understand is when you should think about it and when you shouldn’t, i.e. when applying it will matter and when it won’t.”
The Coriolis Effect — General Physics
The Coriolis Effect is the apparent deflection of moving objects when the motion is described relative to a rotating reference frame. The Coriolis force acts in a direction perpendicular to the rotation axis and to the velocity of the body in the rotating frame and is proportional to the object’s speed in the rotating frame.
A commonly encountered rotating reference frame is the Earth. The Coriolis effect is caused by the rotation of the Earth and the inertia of the mass experiencing the effect. Because the Earth completes only one rotation per day, the Coriolis force is quite small, and its effects generally become noticeable only for motions occurring over large distances and long periods of time. This force causes moving objects on the surface of the Earth to be deflected to the right (with respect to the direction of travel) in the Northern Hemisphere and to the left in the Southern Hemisphere. The horizontal deflection effect is greater near the poles and smallest at the equator, since the rate of change in the diameter of the circles of latitude when travelling north or south, increases the closer the object is to the poles. (Source: Wikipedia)
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Thomas Haugland, a Shooters’ Forum member from Norway, is a long-range target shooter and hunter. He has created an interesting video showing how to gauge wind velocities by watching trees, grass, and other natural vegetation. The video commentary is in English, but the units of wind speed (and distance) are metric. Haugland explains: “This is not a full tutorial, but rather a short heads-up to make you draw the lines between the dots yourself”. Here are some conversions that will help when watching the video:
.5 m/s = 1.1 mph | 1 m/s = 2.2 mph | 2 m/s = 4.5 mph
3 m/s = 6.7 mph | 4 m/s = 8.9 mph | 5 m/s =11.2 mph
Bryan Litz with his F-TR Nat’l Championship-winnning rifle, and the man who built it, John Pierce.
Bryan Litz knows something about bullet shapes and dimensions. He’s the chief designer of many of Berger’s projectiles, including the successful line of Hybrid bullets. Bryan also understands how bullets actually perform in “real world” competition. Bryan won BOTH the Mid-Range and Long-Range National F-TR Championships this year, a remarkable accomplishment. With Bryan’s technical expertise combined with his shooting skills, few people are better qualified to answer the question: “how should I sort bullets when loading for competition?”
Bullet Sorting Strategies — OAL vs. Base to Ogive
At the 2015 Berger Southwest Nationals, Forum member Erik Cortina cornered Bryan Litz of Applied Ballistics. Erik was curious about bullet sorting. Knowing that bullets can be sorted by many different criteria (e.g. weight, overall length, base to ogive length, actual bearing surface length etc.) Erik asked Bryan to specify the most important dimension to consider when sorting. Bryan recommended sorting by “Base to Ogive”. Litz noted that: “Sorting by overall length can be misleading because of the nature of the open-tip match bullet. You might get a bullet that measures longer because it has a jagged [tip], but that bullet might not fly any different. But measuring base to ogive might indicate that the bullet is formed differently — basically it’s a higher resolution measurement….”
Here’s a valuable web resource our readers should bookmark for easy access in the future. ShootForum.com offers a vast Bullet Database, which includes roughly 3900 bullet designs in all. We counted nearly 200 different 6mm bullets! The bullet info comes from the makers of QuickLOAD Software. Access to the online database is FREE. Most database entries include Caliber, Manufacturer, Stated Bullet Weight, True Bullet Weight, Length, Sectional Density (SD), and Ballistic Coefficient.* In many cases multiple BCs are provided for different velocity ranges.
The database is great if you’re looking for an unusual caliber, or you want a non-standard bullet diameter to fit a barrel that is tighter or looser than spec. You’ll find the popular jacketed bullets from major makers, plus solids, plated bullets, and even cast bullets. For those who don’t already own QuickLOAD software, this is a great resource, providing access to a wealth of bullet information.
Values for Changed Bullet Designs
Some of our readers have noted some variances with BCs and OALs with recently changed bullet designs. In general the database is very useful and accurate. However, as with any data resource this extensive, there will be a few items that need to be updated. Manufacturers can and do modify bullet shapes. Kevin Adams, one of the creators of the database, explains: “Thanks for mentioning this database. It took us a long time to collate this information and have agreement to publish it. Please keep in mind that individual batches of bullets will differ from the manufacturers’ stated standards. This is more a reflection on the manufacturers’ tolerances than the database ‘accuracy’. We will continue to add to the database as more manufacturers’ figures come available.”
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That smart phone in your pocket is really a miniature computer. What if you could harness that electronic brain to work as a weather meter? You’d just need a way to feed the smart phone environmental data — temperature, humidity, air pressure, wind velocity and so on. Well now that’s possible with the new $69.00 Weatherflow Smart Phone Weather Meter.
This portable, multi-function Weather Meter provides key weather data to your iOS and Android Mobile devices wirelessly via BlueTooth. The unit measures temperature, humidity, air pressure and dew points. With its built-in impeller, the Weather Meter will also record wind speed (average and gust), and wind direction. You can hand-hold it or attach it to a pole/tripod with a standard camera mount. This wireless Weather Meter is compatible with iPhone, iPad, iPod Touch and all major Android devices. The best thing is the price — right now the unit is just $69.00 at Amazon.com.
Reviews by Weather Meter Purchasers
By Wiley on October 2, 2015 — Verified Purchase
I own and love the original WeatherFlow Wind Meter but when I saw this new one that includes temperature, humidity and pressure for under $100, I had to have it. My new weather meter arrived two days after I ordered it and I am amazed at how good this thing is. Solid and well-built, it’s super comfortable in your hand. The hard carry case is nice. The App is pretty simple – start the App and push the button to connect. The meter connected without issue to my iPad mini and my Galaxy S5 (Android) phone. It displays the extra sensor information elegantly, and the data agrees very well with the Davis weather station on my neighbor’s house. Saving and sharing reports is simple. Something cool that’s not obvious until you play with the App a bit are the ‘more data’ you can see (wind chill, heat index, crosswind, headwind, and many others including some I didn’t know existed). I’ve used various Kestrel meters over years and while they are good sensors, Kestrel’s higher price and lack of smart phone integration (or any easy way to get data off the thing) have been frustrating. [Editor: Kestrel’s brand new 5000 Series Weather Meters do offer Bluetooth connectivity as an optional extra.]
By Richard W. on October 27, 2015 — Verified Purchaser
Great device for the price. It would be nice to interface it with ballistics Apps… but it provides relatively accurate readings and is very small. Finding wind direction is a bit manual (you have to face the device into the wind), but how hard is that? The Bluetooth connectivity is great, you don’t actually have to have it physically connected to the phone — you can put it where you need it.
Technical Details — Compatibility and Settings
The WeatherFlow Weather Meter processes data via a free downloadable App for iOS or Android. The unit works with Apple iPhones 4S or newer, Apple iPads Gen 3 or newer, iPod Touch, and “all major Android devices”. Wireless functionality requires support for Bluetooth version 4.0. You can select either English or Metric units via the “settings” menu. Wind speed units/range are 0.5 to 140 mph; 0.4 to 122 Knots; 0.8 to 225 kph; 0.2 to 63 m/s. Pressure units/range are: 8.9 to 32.5 inHg; 300 to 1100 mbar.
Product Tip from Boyd Allen. We welcome reader submissions.
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Applied Ballistics LLC will offer its first-ever Ballistics Seminar early next year in Tustin, Michigan. This two-day seminar will feature Ballistician Bryan Litz and other experts including Eric Stecker, President of Berger Bullets, and Ray Gross, Captain of the U.S. F-TR Rifle Team. Bryan, the primary speaker, will present material from his books, the Applied Ballistics Lab, and his experience shooting in various disciplines. Bryan recently won both the Mid-Range and Long-Range F-TR National Championships. Bryan will be assisted by Nick Vitalbo, Owner of nVisti Tactical Innovations and lead engineer for Applied Ballistics. The seminar, held February 29 through March 1, 2016, will include classroom sessions followed by live fire demonstrations with sophisticated instrumentation.
Ballistic Solvers – How they work, best practices, demos.
Weapon Employment Zone (WEZ) Analysis – How to determine and improve hit percentage.
Optics and Laser Technology — State of the Art.
The seminar costs $500.00. But consider this — each seminar participant will receive the entire library of Applied Ballistics books and DVDs, valued at $234.75, PLUS a free copy of Applied Ballistics Analytics software, valued at $200.00. So you will be getting nearly $435.00 worth of books, DVDs, and software. In addition, a DVD of the seminar will be mailed to each attendee after the seminar concludes.
Bryan Litz explains: “Subjects will be introduced from an academic-first, principles perspective. Once the scientific basis for the material is established, the ideas are further demonstrated with examples from instrumented live fire. We explain the science, and then present examples of the principles in action. You’ll leave with an understanding of the subject matter, as well as a knowledge of how to apply it in the real world.” To learn more about the Ballistics Seminar, read this AccurateShooter Forum Thread.
Early Bird Special — Save $100.00
If you register before the end of December, 2015, you’ll receive $100.00 off the regular $500 registration fee. This $400.00 Early Bird Special price can be secured by registering through the Applied Ballistics online store.
The two-day seminar will be held at the Kettunen Center in Tustin Michigan. Lodging costs range from $115-$240 (all-inclusive). This price includes three meals each day, and starts at 3:00 pm the day before the seminar, and goes to breakfast the morning after the seminar concludes. Contact the Kettunen Center directly to reserve accommodations.
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Have you recently purchased a new scope? Then you should verify the actual click value of the turrets before you use the optic in competition (or on a long-range hunt). While a scope may have listed click values of 1/4-MOA, 1/8-MOA or 0.1 Mils, the reality may be slightly different. Many scopes have actual click values that are slightly higher or lower than the value claimed by the manufacturer. The small variance adds up when you click through a wide range of elevation.
In this video, Bryan Litz of Applied Ballistics shows how to verify your true click values using a “Tall Target Test”. The idea is to start at the bottom end of a vertical line, and then click up 30 MOA or so. Multiply the number of clicked MOA by 1.047 to get the claimed value in inches. For example, at 100 yards, 30 MOA is exactly 31.41 inches. Then measure the difference in your actual point of impact. If, for example, your point of impact is 33 inches, then you are getting more than the stated MOA with each click (assuming the target is positioned at exactly 100 yards).
How to Perform the Tall Target Test
The objective of the tall target test is to insure that your scope is giving you the proper amount of adjustment. For example, when you dial 30 MOA, are you really getting 30 MOA, or are you getting 28.5 or 31.2 MOA? The only way to be sure is to verify, don’t take it for granted! Knowing your scopes true click values insures that you can accurately apply a ballistic solution. In fact, many perceived inaccuracies of long range ballistics solutions are actually caused by the scopes not applying the intended adjustment. In order to verify your scope’s true movement and calculate a correction factor, follow the steps in the Tall Target Worksheet. This worksheet takes you thru the ‘calibration process’ including measuring true range to target and actual POI shift for a given scope adjustment. The goal is to calculate a correction factor that you can apply to a ballistic solution which accounts for the tracking error of your scope. For example, if you find your scope moves 7% more than it should, then you have to apply 7% less than the ballistic solution calls for to hit your target.
NOTE: When doing this test, don’t go for the maximum possible elevation. You don’t want to max out the elevation knob, running it to the top stop. Bryan Litz explains: “It’s good to avoid the extremes of adjustment when doing the tall target test.I don’t know how much different the clicks would be at the edges, but they’re not the same.”
Should You Perform a WIDE Target Test Too?
What about testing your windage clicks the same way, with a WIDE target test? Bryan Litz says that’s not really necessary: “The wide target test isn’t as important for a couple reasons. First, you typically don’t dial nearly as much wind as you do elevation. Second, your dialed windage is a guess to begin with; a moving average that’s different for every shot. Whereas you stand to gain a lot by nailing vertical down to the click, the same is not true of windage. If there’s a 5% error in your scope’s windage tracking, you’d never know it.”
Verifying Scope Level With Tall Target Test
Bryan says: “While setting up your Tall Target Test, you should also verify that your scope level is mounted and aligned properly. This is critical to insuring that you’ll have a long range horizontal zero when you dial on a bunch of elevation for long range shots. This is a requirement for all kinds of long range shooting. Without a properly-mounted scope level (verified on a Tall Target), you really can’t guarantee your horizontal zero at long range.”
NOTE: For ‘known-distance’ competition, this is the only mandatory part of the tall target test, since slight variations in elevation click-values are not that important once you’re centered “on target” at a known distance.
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In this video, Bryan Litz of Applied Ballistics talks about Density Altitude and the effect of atmospheric conditions on bullet flight. Bryan explains why you must accurately account for Density Altitude when figuring long-range trajectories.
Bryan tells us: “One of the important elements in calculating a fire solution for long-range shooting is understanding the effect of atmospherics. Temperature, pressure, and humidity all affect the air density that the bullet’s flying through. You can combine all those effects into one number (value) called ‘Density Altitude’. That means that you just have one number to track instead of three. But, ultimately, what you are doing is that you are describing to your ballistics solver the characteristics of the atmosphere that your bullet’s flying through so that the software can make the necessary adjustments and account for it in its calculations for drop and wind drift.”
Density altitude is the altitude relative to the standard atmosphere conditions (ISA) at which the air density would be equal to the indicated air density at the place of observation. Density altitude can be calculated from atmospheric pressure and temperature (assuming dry air). Here is the formula:
Air is more dense at lower elevations primarily because of gravity: “As gravity pulls the air towards the ground, [lower] molecules are subject to the additional weight of all the molecules above. This additional weight means the air pressure is highest at sea level, and diminishes with increases in elevation”.*
Both an increase in temperature, decrease in atmospheric pressure, and, to a much lesser degree, increase in humidity will cause an increase in density altitude. In hot and humid conditions, the density altitude at a particular location may be significantly higher than the true altitude.
Applied Ballistics LLC will release updated editions of two popular resource books: Applied Ballistics for Long-Range Shooting (3rd Edition) and Ballistic Performance of Rifle Bullets (2nd Edition). Retail price is $54.95 for each title, or $94.95 if purchased together. Pre-orders are now being accepted with a $5 discount per book. You can pre-order the new editions through the Applied Ballistics store. The new editions are expected to ship by the second week of December.
Applied Ballistics for Long Range Shooting (ABLRS), Bryan Litz’s “Magnum Opus”, will have significant enhancements. New for the Third Edition is content on Weapon Employment Zone (WEZ) analysis. WEZ analysis is the study of hit percentage, and how that will be affected by the uncertainties in your environment. Existing academic material is augmented with modern experimental findings. The Third Edition also includes a CD-ROM disc with Applied Ballistics’ latest version of its ballistic software. NOTE: The third edition of ABLRS does NOT include the library of bullet data. That bullet library now exists as a separate reference book: Ballistic Performance of Rifle Bullets.
Ballistic Performance of Rifle Bullets — Data for 533 Bullets AND Rimfire Ammo
The updated, Second Edition of Ballistic Performance of Rifle Bullets contains the current library of all modern bullets tested by the Applied Ballistics Laboratory. Expanding on the First Edition, which had data on 400 bullets from .22 to .408 caliber, this Second Edition contains data on 533 bullets from .22 through .50 caliber. In addition to the centerfire bullet data, the Second Edition contains live fire data on 90 types of rimfire ammo which were all tested for muzzle velocity and BC through five different barrels of various twist/length configurations. This library of experimental test data is the most extensive and accurate resource ever assembled for small arms bullets. Numerous modern ballistics programs draw from the library of tested BCs that are published in this book.
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Need a simple, easy-to-use drop chart for your rifle? Something you can tape right to the buttstock? Then check out Hornady’s handy Online Ballistics Calculator. This user-friendly calculator will compute your drops accurately, and output a handy “Cheat Sheet” you can print and attach to your rifle. Simply input G1 or G7 BC values, muzzle velocity, bullet weight, zero range and a few other variables. Click “Calculate” and you’re good to go. You can select the basic version, or an advanced version with more data fields for environmental variables (altitude, temperature, air pressure, and humidity). You can also get wind drift numbers by inputing wind speed and angle.
Conveniently, on the trajectory output, come-ups are listed in both MOA and Mils — so this will work with either MOA clicks or Mil-based clicks. There are more sophisticated ballistics solvers available on the web (such as the outstanding Applied Ballistics Online Calculator), but the Hornady Calculator is very simple and easy to use. If you just want a basic drop chart, you may want to check this out.
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These four photos show the substantial changes in the shock wave and turbulence patterns for the same 7.5mm bullet at different velocities. The “M” stands for Mach and the numerical value represents the velocity of the bullet relative to the speed of sound at the time of the shot. Photos by Beat Kneubuehl.
“Going transonic” is generally not a good thing for bullets. The bullet can lose stability as it enters the transonic zone. It can also become less slippery, losing BC as a consequence of dynamic instability. In this video, Bryan Litz of Applied Ballistics analyzes what happens to bullet stability (and BC) as projectiles approach the speed of sound. Transonic effects come into play starting about Mach 1.2, as the bullet drops below 1340 fps.
Transonic Ballistics Effects Explainedby Bryan Litz
What happens when the bullet slows to transonic speed, i.e. when the bullet slows to about 1340 feet per second? It is getting close to the speed of sound, close to the sound barrier. That is a bad place to fly for anything. In particular, for bullets that are spin-stabilized, what the sound barrier does to a bullet (as it flies near Mach 1) is that it has a de-stabilizing effect. The center of pressure moves forward, and the over-turning moment on the bullet gets greater. You must then ask: “Is your bullet going to have enough gyroscopic stability to overcome the increasing dynamic instability that’s experienced at transonic speed?”
Some bullets do this better than others. Typically bullets that are shorter and have shallow boat-tail angles will track better through the transonic range. On the contrary, bullets that are longer… can experience a greater range of pitching and yawing in the transonic range that will depress their ballistic coefficients at that speed to greater or lesser extents depending on the exact conditions of the day. That makes it very hard to predict your trajectory for bullets like that through that speed range.
When you look at transonic effects on stability, you’re looking at reasons to maybe have a super-fast twist rate to stabilize your bullets, because you’re actually getting better performance — you’re getting less drag and more BC from your bullets if they are spinning with a more rigid axis through the transonic flight range because they’ll be experiencing less pitching and yawing in their flight.
To determine how bullets perform in the “transonic zone”, Bryan did a lot of testing with multiple barrels and various twist rates, comparing how bullets act at supersonic AND transonic velocities. Bryan looked at the effect of twist rates on the bullets’ Ballistic Coefficient (BC). His tests revealed how BC degrades in the transonic zone due to pitching and yawing. Bryan also studied how precision (group size) and muzzle velocity were affected by twist rates. You may be surprised by the results (which showed that precision did not suffer much with faster barrel twist rates). The results of this extensive research are found in Bryan’s book Modern Advancements in Long Range Shooting.
Bryan notes: “A lot of gunpowder was burned to get these results and it’s all published in layman’s terms that are easy to understand”. If you’re interested in learning more about transonic bullet stability, you may want to pick up a copy of Bryan’s book.
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Someone spending thousands of dollars on a once-in-a-lifetime hunt might consider getting Geovid rangefinding binoculars. Leica’s award-winning Geovid combines a superb binocular optic with a laser rangefinder AND a ballistic computer. With this single device you can spot your game, find the distance to your target, and calculate the elevation correction. Geovids even take a micro-SD card so you can upload your customized ballistics table.
At around $3200.00 (street price) Geovids are very expensive, but for a serious hunter the Geovid’s capabilities justify the price*. The glass is excellent, the rangefinder offers outstanding performance, and you never have to pull out a PDA or mobile device to run ballistics. The Geovid even does angle correction and can output elevation click values. With the Geovid, you have one tool that does three jobs exceptionally well. When you’re climbing a mountain in pursuit of a Trophy Elk, carrying less gear makes sense.
Now through October 31, 2015 you can save $300.00 on a new 8×42 Geovid HD-B, or 10×42 Geovid HD-B. That makes this state-of-the-art tool much more affordable. To get a $300.00 mail-in rebate from Leica, submit a sales receipt with the Leica Rebate Form.
*We have a good friend who works as a professional hunting guide and gunsmith in New Mexico. For years he made do with well-used Steiner binoculars and an older Leica LRF. On our last visit to NM, he proudly showed us his new Leica Geovid. I told him: “John, those Geovids cost a fortune… are they really worth the money?” He told me: “On one of my first hunts after getting the Geovid, I took along the Steiners for comparison. It was late in the day. I glassed a ridgeline about 700 yards away with the Steiners, and saw nothing. Then I got out the Geovid, looked at the same area and saw two large Elk in among some trees. That made the hunt a success for me and my client. Yes the Geovids are worth it… the glass really makes a difference in low light. And I can range as I’m spotting — that’s a big deal.”
If you are considering the Geovids, you’ll find that Geovid owners have high praise for these rangefinding binoculars. Here are reviews from verified purchasers who have used Geovids on hunts:
“Optical quality is second to none, these binos are in a class by themselves (the only competition IMHO are the Swarovski EL Range). Direct comparison of optic image quality to my lesser-brand binos really demonstrated the difference for me. The image is bright and clear across the entire field of view which is also wider than my standard 10×42 binos. Low-light gathering capability at dawn and dusk is considerably better than my lesser brands and should extend my evening hunting times by another 5 to 10 minutes. The laser ranging capability is amazing! The reading is almost instantaneous[.] The display is a red open target square that’s easy to see in all light conditions.” — Jackson611
“These Binos are the best range-finders on the market, not even talking about the glass yet. The range report is almost instantaneous. If you choose to load your ballistics data on the SD card you will be glad you did. It gives you bullet drop out to 1000 yards. Now let’s get to the glass. I have Swarovski 15×56 binos. These Leicas are just as clear, but small enough to wear around your neck. The price is high, but I learned a long time ago, that you get what you pay for with optics. And if you hunt out west, your optics will make or break your hunt.” — Matt
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Here’s a great tip from Forum member Greg C. (aka “Rem40X”). Greg has created a trajectory table with windage and elevation data for various distances and wind speeds. Greg prints out a compact version of his drop chart to place on his rifle. While many shooters tape a ‘come-up’ table on their buttstock, Greg has a better solution. He tapes the trajectory table to the outside of his front flip-up scope cover. This way, when he flips up the cover, his data is displayed for easy viewing right in front.
With your ‘come-up’ table on the flip-up cover you can check your windage and elevation easily without having to move up off the rifle and roll the gun over to look at the side of the stock. Greg tells us: “Placing my trajectory table on the front scope cover has worked well for me for a couple of years and thought I’d share. It’s in plain view and not under my armpit. And the table is far enough away that my aging eyes can read it easily. To apply, just use clear tape on the front objective cover.”
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Applied Ballistics has created a new series of YouTube videos about precision long range shooting. Featuring ace long-range shooter and professional ballistician Bryan Litz, these videos will address various topics of interest to long-range marksmen. In this week’s video, the first in the series, Bryan Litz answers the question, “Just What Is Long Range Shooting?” Bryan discusses how we define “long range” and the key factors shooters need to consider.
Applied Ballistics Video — What Is Long Range Shooting?
Bryan states: “I don’t think there is a clear definition of where Long Range starts.” But he offers this practical guideline: “The way I think of it, any time you’re making major adjustments to your zero in order to hit a target, due to gravity drop and wind deflection, THEN you’re getting into ‘Long Range’. For example, if you are zeroed at 100 yards and need to shoot to 600 yards, you have many feet of elevation [drop] to account for, and to me, that’s where it becomes Long Range.”
Extended Long Range and the Transonic Zone
Bryan adds a second concept, namely “Extended Long Range”. Litz says that: “Extended Long Range starts whenever the bullet slows to its transonic range. As the bullet slows down to approach Mach 1, it starts to encounter transonic effects, which are more complex and difficult to account for, compared to the supersonic range where the bullet is relatively well-behaved.” Bryan notes that bullets start to encounter transonic effects at about 1340 fps, quite a bit faster than the speed of sound, which is about 1116 fps at sea level in normal conditions (59° F).
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Warner Tool Company (WTC) has introduced a new series of “Flat Line” ultra-high-BC bullets. These sleek, lathe-turned solids are some of the most perfectly-streamlined projectiles ever sold. The Ballistic Coefficients (BCs) of Flat Line projectiles are as much as 20% higher than other match bullets of similar caliber and weight. For example, the .30-caliber 200gr Flat Line bullet has a claimed G1 BC of 0.780. Compare that to 0.555 for the Sierra 200gr MatchKing and 0.622 for the Berger 200gr Hybrid.
The new Flat Line bullets all show extremely high Ballistic Coefficients for their weights:
WTC also claims that Flat Line bullets can be launched at faster velocities than other bullets of similar caliber and weight. In its marketing materials, WTC says that Flat Line bullets deliver “Higher velocities when compared with projectiles in its weight class [and] much higher velocity when compared with projectiles of similar BC.” For example, WTC claims that “the 155.5gr .30-caliber bullet has the velocity of a 125-135gr bullet [with] the BC of a 185-200gr bullet.” It will be interesting to see if these claims can be verified in field tests.
Here are comparative G1 BCs for a variety of large .30-caliber bullets:
Cal Zant of the Precision Rifle Blog has obtained some early-production Flat Line bullets from their designer, Josh Kunz. Zant has written a lengthy article explaining the design and features of the new Flat Line bullets. If you are considering ordering some of these new lathe-turned solids, you should definitely read Zant’s report.
These bullets were designed by Aerospace engineer Josh Kunz using advanced computational fluid dynamics (CFD) to simulate supersonic air flow around the bullets. Through the use of advanced modeling and precision CNC machining, Kunz has developed extremely uniform, ballistically “slippery” bullets that fly faster and flatter than other projectiles of similar weight/caliber.
Premium Pricing: Flat Line Bullets Cost $125 to $165 per Hundred
These new Flat Line solid bullets are pricey. The 155s cost $1.25 per bullet and the price goes up from there. If you need large quantities of projectiles for a week-long match, the cost can be daunting. One hundred fifty of the 200-grainers will set you back $435.00! Here is a price list for the new Flat Line bullets. All quantities are in boxes of 50. Pricing is introductory and subject to change.
.30 Cal 155 grain
$62.50 per 50-ct box ($1.25 per bullet)
.30 Cal 180 grain
$67.50 per 50-ct box ($1.35 per bullet)
.30 Cal 200 grain
$72.50 per 50-ct box ($1.45 per bullet)
.338 Cal 255 grain
$82.50 per 50-ct box ($1.65 per bullet)
Is the cost worth it? When you look at the overall expense of attending a major match, and the fact that the top places in big matches are sometimes are decided by a single point (or X-Count), some competitors will spend the extra money for these ultra-high BC solids.
How do you build better (more precise) ammo drop tables? With radar, that’s how. Barnes Bullets is using Doppler Radar to develop the drop tables for its new Precision Match line of factory ammunition. The Doppler radar allows Barnes to determine actual velocities at hundreds of points along a bullet’s flight path. This provides a more complete view of the ballistics “behavior” of the bullet, particularly at long range. Using Doppler radar, Barnes has learned that neither the G1 nor G7 BC models are perfect. Barnes essentially builds a custom drag curve for each bullet using Doppler radar findings.
Use of Doppler Radar to Generate Trajectory Solutions
by Barnes Bullets, LLC
Typical trajectory tables are generated by measuring only two values: muzzle velocity, and either time-of-flight to a downrange target, or a second downrange velocity. Depending on the test facility where this data is gathered, that downrange target or chronograph may only be 100 to 300 yards from the muzzle. These values are used to calculate the Ballistic Coefficient (BC value) of the bullet, and the BC value is then referenced to a standardized drag curve such as G1 or G7 to generate the trajectory table.
This approach works reasonably well for the distances encountered in most hunting and target shooting conditions, but breaks down rapidly for long range work. It’s really an archaic approach based on artillery firings conducted in the late 1800s and computational techniques developed before the advent of modern computers.
There is a better approach which has been utilized by modern militaries around the world for many years to generate very precise firing solutions. Due to the sizeable investment required, it has been slow to make its way into the commercial market. This modern approach is to use a Doppler radar system to gather thousands of data points as a bullet flies downrange. This radar data is used to generate a bullet specific drag curve, and then fed into a modern 6 Degree of Freedom (DOF) [ballistics software program] to generate precise firing solutions and greatly increase first-round hit probability. (The 6 DOF software accounts for x, y, and z position along with the bullet’s pitch, yaw, and roll rates.)
Barnes has invested heavily in this modern approach. Our Doppler radar system can track bullets out to 1500 meters, recording the velocity and time of flight of that bullet every few feet along the flight path. Consider the graph below showing a bullet specific drag curve referenced to the more common G1 and G7 curves:
Neither of the standard curves is a particularly good match to our test bullet. In the legacy approach to generating a downrange trajectory table, the BC value is in effect a multiplier or a fudge factor that’s used to shift the drag curve of the test bullet to try and approximate one of the standard curves. This leads to heated arguments as to which of the standardized drag curves is a better fit, or if multiple BC values should be used to better approximate the standard curve (e.g., use one BC value when the velocity is between Mach 1 and Mach 2, and a different BC value when the velocity is between Mach 2 and Mach 3.) Barnes’ approach to creating trajectory tables is to generate bullet-specific drag curves, and use that data directly in a modern, state-of-the-art, 6 DOF ballistics program called Prodas to generate the firing solution.
Story tip from EdLongrange. We welcome reader submissions.
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We know our readers are curious about the new Tipped MatchKings (TMKs) introduced by Sierra Bullets this year. Our friend Bill at Rifleshooter.com got hold of some of the .30-Cal 175-grain TMKs and tested them in his .308 Win rifle. He found the bullets were very consistent in weight. As for bearing surface, the SD was fairly low (.002″), but measurements varied from 0.400″ to 0.407″. Seven-thousandths extreme spread is more than we like to see, as it may affect accuracy. Therefore we recommend you sort by bearing surface length before loading these in match rounds.
Photo shows Bryan Litz (on right) and tester Mitchell Fitzpatrick. Bryan said: “Only 2,445 rounds to go! We’re testing over 50 ammo types in five different twist barrels… science can be exhausting!”
Do you know the actual BC (Ballistic Coefficient) of your rimfire ammunition? Well Applied Ballisitics will soon have answers for you. Bryan Litz and his team of testers have been working on a Herculean project. They’ve been testing over fifty types of .22 LR ammo, using five different twist-rate barrels.
Applied Ballistics has just released a fully upgraded version of its popular Tactical App for Android devices. Bryan Litz tells us: “AB Tactical has received a major overhaul (including a new Bullet Library with over 420 options). The upgrade will require that you uninstall the previous version that you have of the application and then install this new version. This is due to the complete re-write of the internal database handling.” NOTE: You need to record your gun-specific data before you install the new version. Details of the updated AB Tactical App are featured in the new 19-page USER Manual.
NOTE: This upgrade is for the Applied Ballistics Tactical Version only. There is no iPhone version of this App, and this is not the standard app that can be purchased from Google Play, or iTunes.
The new version of AB Tactical has a host of important enhancements: