Why You CANNOT Rely on the MV Printed on the Ammo Box!
When figuring out your come-ups with a ballistics solver or drop chart it’s “mission critical” to have an accurate muzzle velocity (MV). When shooting factory ammo, it’s tempting to use the manufacturer-provided MV which may be printed on the package. That’s not such a great idea says Bryan Litz of Applied Ballistics. Don’t rely on the MV on the box, Bryan advises — you should take out your chrono and run your own velocity tests. There are a number of reasons why the MV values on ammo packaging may be inaccurate. Below is a discussion of factory ammo MV from the Applied Ballistics Facebook Page.
Five Reasons You Cannot Trust the Velocity on a Box of Ammo:
1. You have no idea about the rifle used for the MV test.
2. You have no idea what atmospheric conditions were during testing, and yes it matters a lot.
3. You have no idea of the SD for the factory ammo, and how the manufacturer derived the MV from that SD. (Marketing plays a role here).
4. You have no idea of the precision and quality of chronograph(s) used for velocity testing.
5. You have no idea if the manufacturer used the raw velocity, or back-calculated the MV. The BC used to back track that data is also unknown.
1. The factory test rifle and your rifle are not the same. Aside from having a different chamber, and possibly barrel length some other things are important too like the barrel twist rate, and how much wear was in the barrel. Was it just recently cleaned, has it ever been cleaned? You simply don’t know anything about the rifle used in testing.
2. Temperature and Humidity conditions may be quite different (than during testing). Temperature has a physical effect on powder, which changes how it burns. Couple this with the fact that different powders can vary in temp-stability quite a bit. You just don’t know what the conditions at the time of testing were. Also a lot of factory ammunition is loaded with powder that is meter friendly. Meter friendly can often times be ball powder, which is less temperature stable than stick powder often times.
3. The ammo’s Standard Deviation (SD) is unknown. You will often notice that while MV is often listed on ammo packages, Standard Deviation (normally) is not. It is not uncommon for factory ammunition to have an SD of 18 or higher. Sometimes as high as 40+. As such is the nature of metering powder. With marketing in mind, did they pick the high, low, or average end of the SD? We really don’t know. You won’t either until you test it for yourself. For hand-loaded ammo, to be considered around 10 fps or less. Having a high SD is often the nature of metered powder and factory loads. The image below is from Modern Advancements in Long Range Shooting: Volume II.
4. You don’t know how MV was measured. What chronograph system did the manufacturer use, and how did they back track to a muzzle velocity? A chronograph does not measure true velocity at the muzzle; it simply measures velocity at the location it is sitting. So you need to back-calculate the distance from the chrono to the end of the barrel. This calculation requires a semi-accurate BC. So whose BC was used to back track to the muzzle or did the manufacturer even do that? Did they simply print the numbers displayed by the chronograph? What kind of chronograph setup did they use? We know from our Lab Testing that not all chronographs are created equal. Without knowing what chronograph was used, you have no idea the quality of the measurement. See: Applied Ballistics Chronograph Chapter Excerpt.
5. The MV data may not be current. Does the manufacturer update that data for every lot? Or is it the same data from years ago? Some manufacturers rarely if ever re-test and update information. Some update it every lot (ABM Ammo is actually tested every single lot for 1% consistency). Without knowing this information, you could be using data for years ago.
CONCLUSION: Never use the printed MV off a box of ammo as anything more than a starting point, there are too many factors to account for. You must always either test for the MV with a chronograph, or use carefully obtained, live fire data. When you are using a Ballistic Solver such as the AB Apps or Devices integrated with AB, you need to know the MV to an accuracy down to 5 fps. The more reliable the MV number, the better your ballistics solutions.
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There is nothing more frustrating (or embarassing) than sending a live round into your expensive new chronograph. As the photo below demonstrates, with most types of chronographs (other than the barrel-hung Magnetospeed), you can fatally injure your expensive chrono if it is not positioned precisely.
When setting up a chrono, we always unload the rifle, remove the bolt and bore-sight to ensure that the path of the bullet is not too low. When bore-sighting visually, set up the rifle securely on the sandbags and look through the bore, breech to muzzle, lining up the barrel with your aim point on the target. Then (during an appropriate cease-fire), walk behind the chronograph. Looking straight back through the “V” formed by the sky-screens, you should be able to see light at the end of the barrel if the gun is positioned correctly. You can also use an in-chamber, laser bore-sighter to confirm the visual boresighting (see photo).
Adjust the height, angle and horizontal position of the chronograph so the bullet will pass through the middle of the “V” below the plastic diffusers, no less than 5″ above the light sensors. We put tape on the front sky-screen supports to make it easier to determine the right height over the light sensors.
Use a Test Backer to Confirm Your Bullet Trajectory
You can put tape on the support rods about 6″ up from the unit. This helps you judge the correct vertical height when setting up your rifle on the bags. Another trick is to hang a sheet of paper from the rear skyscreen and then use a laser boresighter to shine a dot on the paper (with the gun planted steady front and rear). This should give you a good idea (within an inch or so) of the bullet’s actual flight path through the “V” over the light sensors. Of course, when using a laser, never look directly at the laser! Instead shine the laser away from you and see where it appears on the paper.
Alignment of Chronograph Housing
Make sure the chrono housing is parallel to the path of the bullet. Don’t worry if the unit is not parallel to the ground surface. What you want is the bullet to pass over both front and rear sensors at the same height. Don’t try to set the chrono height in reference to the lens of your scope–as it sits 1″ to 2″ above your bore axis. To avoid muzzle blast interference, set your chronograph at least 10 feet from the end of the muzzle (or the distance recommended by the manufacturer).
Rifles with Elevated Iron Sights
All too often rookie AR15 shooters forget that AR sights are positioned roughly 2.4″ above the bore axis (at the top of the front sight blade). If you set your bullet pass-through point using your AR’s front sight, the bullet will actually be traveling 2.4″ lower as it goes through the chrono. That’s why we recommend bore-sighting and setting the bullet travel point about 5-8″ above the base of the sky-screen support shafts. (Or the vertical distance the chronograph maker otherwise recommends). NOTE: You can make the same mistake on a scoped rifle if the scope is set on very tall rings, so the center of the cross-hairs is much higher than the bore axis line.
TARGET AIM POINT: When doing chrono work, we suggest you shoot at a single aiming point no more than 2″ in diameter (on your target paper). Use that aiming point when aligning your chrono with your rifle’s bore. If you use a 2″ bright orange dot, you should be able to see that through the bore at 100 yards. Using a single 2″ target reduces the chance of a screen hit as you shift points of aim. If you shoot at multiple target dots, place them in a vertical line, and bore sight on the lowest dot. Always set your chron height to set safe clearance for the LOWEST target dot, and then work upwards only.
Other Chronograph Tips from Forum Members:
When using a chronograph, I put a strip of masking tape across the far end of the skyscreens about two-thirds of the way up. This gives me a good aiming or bore-sighting reference that’s well away from the pricey bits. I learned that one the hard way. — GS Arizona
A very easy and simple tool to help you set up the chronograph is a simple piece of string! Set your gun (unloaded of course) on the rest and sight your target. Tie one end of the string to the rear scope ring or mount, then pull the string along the barrel to simulate the bullet path. With the string showing the bullet’s path, you can then easily set the chronograph’s placement left/right, and up/down. This will also let you set the chrono’s tilt angle and orientation so the sensors are correctly aligned with the bullet path. — Wayne Shaw
If shooting over a chrono from the prone position off a bipod or similar, beware of the muzzle sinking as recoil causes the front of the rifle to drop. I “killed” my first chronograph shooting off a gravel covered firing point where I’d not given enough clearance to start with and an inch or two drop in the muzzle caused a bullet to clip the housing. — Laurie Holland
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The U.S. Army Marksmanship Unit (USAMU) regulary publishes “how-to” articles on the USAMU Facebook page. One informative “Handloading Hump Day” article covers 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.
MagnetoSpeed’s technology has completely changed the market for firearms chronographs. With a MagnetoSpeed barrel-mounted chrono you can quickly and easily record muzzle velocity (MV) without having to set up tripods or walk down-range. The compact MagnetoSpeed chronos are easy to set up and transport. With the full-featured V3 model, everything you need comes in a small fitted case. In the top photo are the components used with the MagnetoSpeed V3 Kit:
1. V3 Bayonet sensor
2. Display and control unit
3. Bayonet spacers (plastic and rubber)
4. Cords and mounting hardware (left), suppressor heat shield (right)
5. Alignment rod (square cross-section)
6. Rail adapter (sold separately)
Our friend Gavin Gear of UltimateReloader.com recently reviewed the MagnetoSpeed V3 and came away impressed. Gavin explains the a good chrono is essential: “If you want to load and shoot precision ammunition, you need the tools that will produce and validate the precision of your loads. A good chronograph is one of those tools! In this post I’m going to introduce you to the MagnetoSpeed V3 chonograph, the high-end electromagnetic chronograph which fills out the top slot in MagnetoSpeed’s equipment portfolio.”
In this 11-minute video Gavin reviews MagnetoSpeed’s top-of-the-line V3 Chronograph. He shows what ships with the unit, how to set it up for both rifles and pistols, and then he puts it through its paces showing how it captures velocity data. Gavin says he will follow-up with future videos showing how to link the MagnetoSpeed V3 to your mobile phone and how to log velocity data for future reference. To learn more about this high-tech chrono, visit UltimateReloader.com.
We see comparison tests of cars, cameras, and other hardware. But how about chronographs? What could we learn by setting up three different chronographs, and running a 20-shot string over all three at the same time. One of our Forum members, Randy S. (aka AAA) did that very test with three of the best chronographs you can buy: LabRadar, MagnetoSpeed, and an Oehler model 35P. The MagnetoSpeed was attached to the barrel of an F-Class rig, with the LabRadar placed on the left side of the shooting bench. The Oehler 35P was positioned about 23 feet downrange. The photo above shows the set-up. A 20-shot string was recorded with the results in a spreadsheet.
AAA talks about this interesting experiment in a Shooters’ Forum Thread. Here is his report:
Comparison Testing Three Chronographs
We all have our favorite chronograph. Each gives a number, but how would that number compare to the same round fired with another chronograph? I wanted to know so a friend and I set up the following test with three chronographs: LabRadar, MagnetoSpeed V3, and Oehler Model 35P.
For the test we fired Berger 105gr VLDs over the three chronographs simultaneously. The test rifle was my 6mm BR Ackley (BRA) F-class rig with fire-formed brass and 200 rounds on the new barrel.
Chronogaphs Tested
LabRadar
MagnetoSpeed V3
Oehler Model 35P
Temperature: 86 deg. F
Elevation: 854 feet
Cartridge: 6mm BRA (105gr Berger VLD)
Time between shots: 45 seconds
To start off, five rounds were fired to make sure all systems were recording and to warm the barrel. Then the test was 20 shots fired across all three instruments with 45 seconds between shots. The Oehler was set 7.5 yards from the muzzle so 12 FPS was added to the recorded value.
We were using the internal trigger on the LabRadar. The manual says the Vo indicated is the actual muzzle velocity when using the internal trigger, but not if using the Doppler. The 12 FPS Oehler adjustment (back to MV) was based on the Berger Ballistics Calculator.
Results of the Triple Chronograph Shoot-Out:
LR-M is FPS variance between LabRadar and MagnetoSpeed V3. LR-O is FPS variance between LabRadar and distance-adjusted Oehler 35P. You can see all three chronos were very consistent. SD was identical with the LabRadar and MagnetoSpeed.CLICK HERE for spreadsheet.
The tester, Randy S. (aka AAA) says: “Judge for yourself, but I was impressed by all.”
Comments by Forum Members
Our Forum members expressed interest in this Triple Chronograph test. Some confirmed that the LabRadar and Magnetospeed give very similar FPS numbers, based on their own tests:
“Great test and thanks for sharing. I’ve tested my MagnetoSpeed and LabRadar together and results are always within 2-4 FPS of one another.” — Big D
“Very happy to see your numbers support my decision to buy a MagnetoSpeed. Had read reports comparing it to the Oehler and the numbers I get seem to be supported by my long range shooting results. Many thanks for taking the time and effort [to perform] this comparative test. Always good to get actual test results.” — Texas10
“I did a 4-shot test with my MagnetoSpeed and another shooter’s LabRadar a couple of days ago. The results were within 4 fps with the LabRadar being optimistic.” — Pat Miles
Forum Member Powderbreak studied AAA’s original spreadsheet from the chronograph trio test, then figured out the shot-by-shot FPS variance between the machines. He concluded that all the machines performed very well. Powderbreak posted:
Analyzing the Triple Chronograph Test — What Can We Conclude?
AAA did a great job of comparing the 3 chronos. What conclusions can be drawn?
1) I have not checked the manufacturer’s claims of accuracy, but the three chronos are very close to one another. There is no way for us to determine the actual true velocities, but we do not need to do so. Any of the chronos would be more than adequate for an accurate shooter.
2) The resolution of the three chronographs is actually pretty astounding. One foot per second (FPS) is a resolution of 0.033%.
3) AAA did a great job of reloading a very consistent round. With an extreme spread of 33 fps out of 3014 for 20 rounds, that is only 1.09% total spread of velocities.
4) There is a closer velocity match between the MagnetoSpeed and the LabRadar, but that does not mean the Oehler is less accurate. There is simply an offset between the Oehler and the other two. This could be due to the greater distance, the location, or the internal working of the Oehler.
5) Believe your chronograph, it is probably the most accurate reloading tool that you own.
Brian Litz of Applied Ballistics carefully explained the operation, set-up, accuracy and comparison of AB’s chronographs in his books. [Those books] are well worth the money, and give great insight into the workings of chronographs.” — Powderbreak
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If you didn’t catch our Deals of the Week last Monday, here’s another “heads up”. If you’re thinking of getting a LabRadar chronograph, now’s the time to buy. You can save $50.00 on this unit now through June 24, 2018. Take note — these devices are controlled with MAP pricing, so you won’t see other discounts. This is a factory-authorized, once-a-year Summer Sale.
This sale is notable because you never see this discounted below the $559.95 MAP price. The sale extends through 6/24/2018. You can get the LabRadar from top vendors including Creedmoor Sports, Bruno Shooters Supply, and Midsouth Shooters Supply.
About the LabRadar Chronograph
The LabRadar is probably the most sophisticated chronograph system ever offered to the general public. It is extremely precise yet easy to deploy. The LabRadar’s Doppler Radar technology offers many advantages compared to the traditional analog chrono — no tripods needed, no ambient light required, works on any type of projectile, no matter what caliber or speed. The LabRadar records all shot velocities, then calculates velocity extreme spread (ES), average velocity, and standard deviation (SD). It can also export all your shot data to your computer or laptop. And very soon a new LabRadar Mobile App will be offered that will let you control your LabRadar with an iOS or Android smartphone.
The LabRadar Ballistic Velocity Doppler Radar Chronograph can track a wide range of devices, calibers, and projectiles. It works with airguns, handguns, rifles — even suppressed weapons. (It can even time arrows fired from bows.) A key advantage of the LabRadar is that is can be set to the SIDE of your rifle — you don’t need to go downrange to set up screens on a tripod. You can put the LabRadar right on the bench. Ace shooter and bullet-maker Bart Sauter even uses his LabRadar during matches.
Full LabRadar Field Test/Review by Ray Gross
If you are considering purchasing a LabRadar Chronograph system, we strongly suggest you read the very thorough and informative LabRadar Review by Ray Gross, past Captain of the USA F-TR team.
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LabRadar owners can celebrate. New mobile-friendly control software is coming soon. Gunsmith and Benchrest Hall of Famer Thomas “Speedy” Gonzalez had some interesting news from the NRA Show in Dallas. He learned that the creators of the LabRadar chronograph systems will soon offer Mobile Apps that can run on your iOS or Android smartphone or tablet. This new software will make it much easier to control the LabRadar, and offer enhanced data editing functionality.
New LabRadar iOS and Android Mobile Apps Coming Soon…
Speedy says: “I just got back from the NRA show in Dallas, Texas. The coolest thing I personally saw at the show was at the LabRadar booth. They had the Beta versions of their new LabRadar Apps for the iPhone and Android phones. These Apps let you control all LabRadar functions from your phone as well as your tablet via Bluetooth connection. The new Apps will also allow the LabRadar owner to store and edit his or her data from a much larger and user friendly screen.”
That’s good news. We particularly like the ability to edit LabRadar data on a tablet. Speedy added: “This is going to revolutionize this great product and make it [much more] user-friendly.”
The new LabRadar Mobile Apps will be available free for LabRadar owners. If you own a LabRadar, be sure to register your LabRadar on the LabRadar Website. That will ensure you are notified via email as soon as the software is available. To register, look for the text link at the top right of the LabRadar homepage. It says “Register your LabRadar “. Click the link then fill out the data form.
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MagnetoSpeed’s technology has completely changed the market for firearms chronographs. With a MagnetoSpeed barrel-mounted chrono you can quickly and easily record muzzle velocity (MV) without having to set up tripods or walk down-range. The compact MagnetoSpeed chronos are easy to set up and transport. With the full-featured V3 model, everything you need comes in a small fitted case. In the top photo are the components used with the MagnetoSpeed V3 Kit:
1. V3 Bayonet sensor
2. Display and control unit
3. Bayonet spacers (plastic and rubber)
4. Cords and mounting hardware (left), suppressor heat shield (right)
5. Alignment rod (square cross-section)
6. Rail adapter (sold separately)
Our friend Gavin Gear of UltimateReloader.com recently reviewed the MagnetoSpeed V3 and came away impressed. Gavin explains the a good chrono is essential: “If you want to load and shoot precision ammunition, you need the tools that will produce and validate the precision of your loads. A good chronograph is one of those tools! In this post I’m going to introduce you to the MagnetoSpeed V3 chonograph, the high-end electromagnetic chronograph which fills out the top slot in MagnetoSpeed’s equipment portfolio.”
In this 11-minute video Gavin reviews MagnetoSpeed’s top-of-the-line V3 Chronograph. He shows what ships with the unit, how to set it up for both rifles and pistols, and then he puts it through its paces showing how it captures velocity data. Gavin says he will follow-up with future videos showing how to link the MagnetoSpeed V3 to your mobile phone and how to log velocity data for future reference. To learn more about this high-tech chrono, visit UltimateReloader.com.
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.
There is nothing more frustrating (or embarassing) than sending a live round into your expensive new chronograph. As the photo below demonstrates, with most types of chronographs (other than the barrel-hung Magnetospeed), you can fatally injure your expensive chrono if it is not positioned precisely.
When setting up a chrono, we always unload the rifle, remove the bolt and bore-sight to ensure that the path of the bullet is not too low. When bore-sighting visually, set up the rifle securely on the sandbags and look through the bore, breech to muzzle, lining up the barrel with your aim point on the target. Then (during an appropriate cease-fire), walk behind the chronograph. Looking straight back through the “V” formed by the sky-screens, you should be able to see light at the end of the barrel if the gun is positioned correctly. You can also use an in-chamber, laser bore-sighter to confirm the visual boresighting (see photo).
Adjust the height, angle and horizontal position of the chronograph so the bullet will pass through the middle of the “V” below the plastic diffusers, no less than 5″ above the light sensors. We put tape on the front sky-screen supports to make it easier to determine the right height over the light sensors.
Use a Test Backer to Confirm Your Bullet Trajectory
You can put tape on the support rods about 6″ up from the unit. This helps you judge the correct vertical height when setting up your rifle on the bags. Another trick is to hang a sheet of paper from the rear skyscreen and then use a laser boresighter to shine a dot on the paper (with the gun planted steady front and rear). This should give you a good idea (within an inch or so) of the bullet’s actual flight path through the “V” over the light sensors. Of course, when using a laser, never look directly at the laser! Instead shine the laser away from you and see where it appears on the paper.
Alignment of Chronograph Housing
Make sure the chrono housing is parallel to the path of the bullet. Don’t worry if the unit is not parallel to the ground surface. What you want is the bullet to pass over both front and rear sensors at the same height. Don’t try to set the chrono height in reference to the lens of your scope–as it sits 1″ to 2″ above your bore axis. To avoid muzzle blast interference, set your chronograph at least 10 feet from the end of the muzzle (or the distance recommended by the manufacturer).
Rifles with Elevated Iron Sights
All too often rookie AR15 shooters forget that AR sights are positioned roughly 2.4″ above the bore axis (at the top of the front sight blade). If you set your bullet pass-through point using your AR’s front sight, the bullet will actually be traveling 2.4″ lower as it goes through the chrono. That’s why we recommend bore-sighting and setting the bullet travel point about 5-8″ above the base of the sky-screen support shafts. (Or the vertical distance the chronograph maker otherwise recommends). NOTE: You can make the same mistake on a scoped rifle if the scope is set on very tall rings, so the center of the cross-hairs is much higher than the bore axis line.
TARGET AIM POINT: When doing chrono work, we suggest you shoot at a single aiming point no more than 2″ in diameter (on your target paper). Use that aiming point when aligning your chrono with your rifle’s bore. If you use a 2″ bright orange dot, you should be able to see that through the bore at 100 yards. Using a single 2″ target reduces the chance of a screen hit as you shift points of aim. If you shoot at multiple target dots, place them in a vertical line, and bore sight on the lowest dot. Always set your chron height to set safe clearance for the LOWEST target dot, and then work upwards only.
Other Chronograph Tips from Forum Members:
When using a chronograph, I put a strip of masking tape across the far end of the skyscreens about two-thirds of the way up. This gives me a good aiming or bore-sighting reference that’s well away from the pricey bits. I learned that one the hard way. — German Salazar
A very easy and simple tool to help you set up the chronograph is a simple piece of string! Set your gun (unloaded of course) on the rest and sight your target. Tie one end of the string to the rear scope ring or mount, then pull the string along the barrel to simulate the bullet path. With the string showing the bullet’s path, you can then easily set the chronograph’s placement left/right, and up/down. This will also let you set the chrono’s tilt angle and orientation so the sensors are correctly aligned with the bullet path. — Wayne Shaw
If shooting over a chrono from the prone position off a bipod or similar, beware of the muzzle sinking as recoil causes the front of the rifle to drop. I “killed” my first chronograph shooting off a gravel covered firing point where I’d not given enough clearance to start with and an inch or two drop in the muzzle caused a bullet to clip the housing. — Laurie Holland
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If you have been waiting to purchase a chronograph… now is a great time to buy. You can get the new-model MagnetoSpeed Sporter for under $180.00. You can set up this device in a few minutes, and you never have to go downrange to fiddle with a tripod or fuss with wires. The MagnetoSpeed Sporter is simple and effective — a no-hassle solution.
We’re impressed by the Sporter chrono (as are other shooters — this unit is selling out nationwide). Like the V3, the Sporter faithfully records shots, even in complete darkness. Shot strings are recorded digitally and can be transferred to a smart phone via MagnetoSpeed’s XFR accessory (and Apps).
The MagnetoSpeed Sporter chrono is less than half the price of previous MagnetoSpeed models. This is big news for shooters who always wanted a MagnetoSpeed but found the $379.00 cost (for V3 model) too pricey. The new Sporter Chronograph costs just $179.99 at Sinclair Int’l and Brownells. It offers most of the features of the more expensive models (see chart below for details) and has a updated sensor. MagnetoSpeed says its new Sporter is “Ideal for contoured rifle barrels (sporter barrels) and long-barreled revolvers.” The Sporter Chronograph Kit (shown above) includes: Bayonet Sensor, 3.5 foot Data Cable, Remote Display (with Battery), Strap with thumb nut, Two V-block spacers, and compact storage box.
Is the MagnetoSpeed good enough? Well consider this, Derek Rodgers uses one of the original (full-size) MagnetoSpeed Chronos for his load development. Rodgers is the only man on the planet to have won BOTH the F-Open and the F-TR National Championship. ‘Nuff said.
See MagnetoSpeed Sporter Chronograph Features Reviewed in Video
Q: Will the Sporter Chrono work with thicker barrel (i.e. greater than 1″ diameter)?
A: The manufacturer recommends the $399.00 V3 model for thicker barrels. But, wink-wink, if you have a 1.25″ barrel you can get this to work, based on what we’ve seen.. If you have a really fat barrel (up to 2.0″ diameter), get the V3. Magnetospeed also says the V3 is needed for airguns, shotguns, and muzzleloaders.
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The Sporter Chrono attaches quickly and easily. It has a 3.5-foot-long cord, and will work with Muzzle Brakes and Flash-hiders up to 2.7″ long.
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“Shooting Chrony” is a product name. “Shooting Chrony” should not describe (post-mortem) what you have been doing to your chronograph. Sooner or later all of us may make a mistake, and ventilate our chronograph. With luck, the bullet just “wings” your chronograph, and the damage is minor. But if you hit the unit smack dab in the middle, you may have to retire your chrono for good.
A while back, Forum member Jeff M. (aka “JRM850″) experienced a “low blow” that put his Shooting Chrony out of commission. With tongue firmly in cheek, Jeff started a Forum thread entitled Chronograph Not Picking Up Shots in Bright Sunlight Anymore. Looking at the photo below, the problem is obvious.
This was Jeff’s first chrono kill in 23 years of use, so we shouldn’t be too critical. Jeff explained: “I didn’t realize a friend was shifting from a 300-yard target to 100 yards.” The agent of destruction was a low-traveling 58gr V-Max running at 3415 fps. What happened? Well, when one is shooting at 300 yards, the trajectory will be higher than at 100 yards. We should say, however, that this may have been a low shot, or the 100-yard aiming point may have been placed lower to the ground (closer to the bottom of the target frame), as compared to the 300-yard aiming point.
When setting up a chrono, we always unload the rifle, remove the bolt and bore-sight to ensure that the path of the bullet is not too low. When bore-sighting visually, set up the rifle securely on the sandbags and look through the bore, breech to muzzle, lining up the barrel with your aim point on the target. Then (during an appropriate cease-fire), walk behind the chronograph. Looking straight back through the “V” formed by the sky-screens, you should be able to see light at the end of the barrel if the gun is positioned correctly. You can also use an in-chamber, laser bore-sighter to confirm the visual boresighting (see photo).
Speedy says: “I just got back from the NRA show in Dallas, Texas. The coolest thing I personally saw at the show was at the LabRadar booth. They had the Beta versions of their new LabRadar Apps for the iPhone and Android phones. These Apps let you control all LabRadar functions from your phone as well as your tablet via Bluetooth connection. The new Apps will also allow the LabRadar owner to store and edit his or her data from a much larger and user friendly screen.”
