- 1 What is GPS vs Galileo vs GLONASS and WAAS?
- 2 Barometric Pressure vs Station Pressure
- 3 What reticles do you have in your app?
- 4 Managing Muzzle Velocity & MV Variation
- 5 I have purchased a Custom Drag Model but it is not showing up.
- 6 Recommended Ballistic Calibration Distance is Too Far.
- 7 If my bullet stability is below 1.5 will the app automatically change my BC?
- 8 I am looking at the Kestrel Elite (5700) vs the K4500 which is better?
- 9 I am looking at a Kestrel vs the App, which one do you recommend most?
- 10 I have the Point Mass Solver that came with the book, how can I get this working on my mobile device?
- 11 I have purchased your app on my mobile device before, I now have a new device, or multiple devices, do I have to pay to download it again?
- 12 I bought the app on Android and now have an iPhone (or vice versa) can I switch platforms?
- 13 Can we input our cosign value in to the application instead of degrees?
- 14 My barrel twist rate is lower than the optimum recommended, will this be a problem?
- 15 I am shooting a plastic tipped bullet, will the stability calculator still work?
- 16 My zero shows to be XXX yards, and not 100 yards, can you help me fix this?
- 17 How important is inputting zero atmosphere?
- 18 I am using two different apps, and my firing solution is 1/2/3 moa off, can you help me please?
- 19 Should I use a G1 or G7 form factor?
- 20 I have a gain twist barrel, or I plan on getting a gain twist barrel, how do I input this/what twist rate should I get?
- 21 Where do I measure from to do a Tall Target Test?
Here you will find frequently asked questions related to Applied Ballistics Apps, Software, and Devices.
Garmin Foretrex® 701 with Applied Ballistics® LLC features GPS, GLONASS, & Galileo. It also features WAAS and Ultratrac. But what does all that mean? Today, we answer this question for you.
What does this mean for a user? The Garmin Foretrex 701 works with every major positioning system in the world, can be coupled with two of them at a time, and offers advanced features to help conserve battery life with maintaining the highest accuracy.
Barometric pressure is also known as sea level corrected pressure, and is what the weather station and airports report because it’s useful for pilots and making weather assessments. Barometric pressure is not the actual air pressure where you are, rather it’s a number that’s corrected to sea level. In order to determine the actual air pressure where you are (which is what the ballistics program cares about), you have to account for the effects of altitude. However if you have a handheld weather meter like a Kestrel, you can measure Station Pressure directly which is the actual air pressure where you are. This is the preferred method of inputting pressure data because it’s one less input and relies on only one measurement instead of two.
A common error is to mistake station pressure for barometric or vice versa. The consequence of this error is that the wrong air density gets applied which degrades the accuracy of trajectory predictions. This error is increasingly more severe the higher up you are above sea level.
Refer to the image on the right for proper set-up of the atmospheric pressure inputs. Note the reference altitude is set to 0 ft in the Kestrel which indicates it’s displaying uncorrected station pressure, and the Pressure is Absolute box is checked in the program indicating it’s using station pressure.
To further clarify the output from the Kestrel, here is an excerpt from the Kestrel user’s manual: “Some final notes – If you wish to know the actual or station pressure for your location (such as for engine tuning), simply set the reference altitude on the BARO screen to “0”. In this case, the Kestrel Meter will not make any adjustment and will display the measured value. (Engine tuning and ballistics software sometimes refer to atmospheric or station pressure as “absolute pressure.” These applications are concerned with the actual air density, as opposed to pressure gradients relating to weather, so barometric pressure is less useful.”
Here is a current list of our reticles in the AB Mobile App:
Gen 2 XR
Leupold Tactical Milling
March FMA-1 3-24 Illum
March FMA-1 3-24
March FMA-1 5-40 Illum
March FMA-1 5-40
March FMA-2 3-24
March FMA-2 5-40
March FML-1 3-24 Illum
March FML-1 3-24
March FML-1 5-40 Illum
March FML-1 5-40
March MTR-1 Illum
March MTR-2 Illum
March MTR-3 Illum
March MTR-4 Illum
Schmidt Bender P4L
Sightron LRMOA 2
Vortex Viper PST EBR-1 FFP
Vortext Viper PST EBR-1 SFP
As a refresher here are a couple bullet points before we get started:
1. Chronographs measure velocity at their location, not Muzzle Velocity. Muzzle Velocity needs to be properly calculated using the bullets BC, and atmospheric information. To read more on this see here: Velocity Decay Article.
2. You should have at least 4 data points from your current lot of powder that are 30 Deg/F (15 Deg/C) apart. It is always best to have data points for the coldest, and warmest points that you normally shoot in.
3. Powder Temperature Sensitivity is non-linear, and will be more stable at certain temperatures than at others. No two powders will act the same.
AB Mobile – First we will go over how to use this in AB Mobile. In AB Mobile you use fps per Degree. Which means how many feet per second the MV shifts per degree of temperature change. This is fairly simple to use, and most powders fill fall between 0.3 – 3.0 fps/deg shift. For example, let’s use the following data. 3010 fps @ 100 deg/F, 2970 fps @ 70 deg/F, 2935 fps @ 40 deg/F & 2895 fps @ 10 deg/F. So we would take the total change in MV and divide by the total change in temp. In this case 105 fps shift / over a 90-degree span. (105/90) = 1.28 fps per degree. So I would enter it into the AB Mobile App as such:
Muzzle Velocity = 3010 FPS (917.4 m/s)
Powder Temp = 100 deg/F (37.8 deg/C)
MV Variation = 1.28 fps (0.39 m/s)
MV Variation IS NOT your SD! Please do not enter your Muzzle Velocity SD in as the variation.
For the rest of the devices, software, and apps you will find a Temp-Table. This is a very simple feature to use. You simply input the Calculated Muzzle Velocity (remember chronographs measure velocity at its location, not MV) and the temperature at the time you tested it. For example, let’s use 3000 fps @ 100 deg/F, 2985 fps @ 70 deg/F, 2968 fps @ 40 deg/F & 2950 fps @ 10 deg/F. You would input this data like this:
Side Note: When using the MV-Temp table, you will not be able to adjust muzzle velocity on your device. This is by design. The MV-Temp table is calibrating the MV based on the current temperature. If you want to be able to adjust this, then you need to turn the Temp-Table off. This is easily done, and I show you how in the video below. If you notice you need to input a velocity, because it’s not following the trend. Say at 87 degrees in the above example you have a velocity of 2998, then you can do this by simply adding that to the table, and it will then adjust how it calculates the MV-Temp Table. If you want to do a MV Calibration, on the device then you must hand input that variable in to the table, or turn the table off. Doing a MV Calibration and trying to save, will not change the MV. Don’t worry, I will show you how to properly do this in the video below. Just know that you cannot do a MV Calibration or adjust the MV the normal way, when you are using a Temp-Table.
Sorting Temp-Table Inputs – The Kestrel will automatically sort them, as seen in the video. The software and apps will not. The proper way to input them in to the software and apps, is in order from hottest to coldest temperature. As indicated by the directions, and seen in the screen shots here.
Google play does not always instantly apply purchases. If you have previously purchased a CDM, and it is not showing up try these two things:
- Make sure you have given google time to process the purchase.
- Try the Restore Purchases Button located in the app. You can find out more about the Restore Purchases Feature in the User Guide: AB Mobile User Guide
Another topic that gets brought up a lot is the ability to shoot the ranges needed to do a Ballistics Calibration. Do note, Ballistics Calibration, for the best results, should be done ONLY at long range. More specifically Long Range in regards to the caliber, or Mach 1.2-0.9. Remember this is system dependent. A 22LR leaves the barrel transonic, while a 338 might go transonic at 1 mile. This is in part due to error reporting, but also because of the accuracy of our test data. Bryan Litz takes great care in making sure the data collected is extremely accurate. So if you are using our Custom Drag Model data, and your firing solution is off in the supersonic range (Mach 1.2+) then the culprit is more than likely your muzzle velocity. Note: Custom Drag Models are NOT G7 BCs and are NOT Banded G7 BCs. You cannot accurately re-create the CDM by using banded BCs. While this does apply to the use of G7 & G1 Drag Models, because the averaged G7 BC is good for most velocities in the supersonic range. If your solution is off, at Mach 1.2+ then you need to calibrate your Muzzle Velocity. Keeping in mind, that sometimes the firing solution is correct, and your turrets might not be tracking perfect can also be a culprit here. For more details on this, reference Accuracy and Precision for Long Range Shooting by Bryan Litz, Ballistic Calibration Article coupled with the Chronograph Performance Review Article.
- AB Mobile App: You will be able to input ranges outside the recommended ranges, however it might cause problems due to both error reporting which is covered in the Ballistic Calibration Article, and the limited distance between points.
- Kestrel: If you attempt to do a DSF (Drop Scale Factor) at too short a distance, it will not accept multiple inputs. They must be done At Mach 1.2 – 0.9 and slower. If you need to adjust in the supersonic range, use the MV (Muzzle Velocity) Calibration.
This is dependent on the shooters needs. The K5 is certainly an upgrade from the K4, however when picking an Elite vs Sportsman or K5 vs K4 shooters have different needs, and we have a guide that helps explain these differences so you can make that decision for yourself: Kestrel Comparison Guide
We recommend the Kestrel over the use of a Phone. The Kestrel has a better battery life (15+ days with Bluetooth off), is more durable (it even floats), and is not reliable on cell service to gather weather information. So the Kestrel will work off the grid (so will the apps, and some like AB Tac are designed for off the grid use) and give you on demand, real time weather data.
I have the Point Mass Solver that came with the book, how can I get this working on my mobile device?
The PM Solver cannot be transferred to a mobile device. It will only run on a PC, or on a Windows Mobile device running an OS similar to Windows 10.
When you encounter AB Software designed to run on a Computer, which is not compatible on mobile devices. You may run that software on netbooks which have become more and more mobile, including 2 in 1 devices where the keyboard will disconnect becoming a tablet. It is possible to run this software on a 2 in 1 platform as long as it contains a full version of Windows 10 such as the Nextbook Flexx and Asus Transformer Books. You must make sure it has windows 10 home and NOT windows mobile in order for it to work. It is also important that the device has a USB Port. Not all netbooks come with USB ports on them Some only have the USB Port on the Keyboard, Nextbook Flexx for example. Meaning you can only use USB Devices while they are docked to the keyboard. This is where 2 in 1 or non detachable devices can be a better choice. While the keyboard does not detach, it does fold behind the screen making it tablet like. Example: Asus Q53UX. While not as small, they maintain all the functionality of a laptop while folded flat. Warning: Some 2 in 1 devices are Windows Mobile and/or Android. Read the specs before you buy. They need to be Windows 10 Home or newer.
I have purchased your app on my mobile device before, I now have a new device, or multiple devices, do I have to pay to download it again?
No, as long as you login with the original login you bought the app under, it can be installed on multiple devices.
No, Google and Apple do not honor purchases made on the others store. We do not have the ability to transfer your purchase from one store to another. Even with all the similarities the apps are actually different. They are different platforms, with different coding.
No, the reason we use positive and negative degrees is that our system calculates for both uphill and downhill firing. While they are similar, the solutions are not exact for each scenario. The system also takes in to account the slowing of the bullet, and the changes in pressure as you go higher/lower in altitude. Giving you a more precise solution vs the improved rifleman’s rule. For more on this read Chapter 4 of Applied Ballistics for Long Range Shooting 3rd Edition.
No. As long as your SG (Gyroscopic Stability) factor is above 1.05. Note the formula has an accuracy to +/- 0.1 SG. Numbers below 1.05 will lose both Accuracy and BC, and most likely tumble. Numbers between 1.05 and 1.45 will have a lower BC but retain Accuracy. Stability levels above 1.5 will have optimum Accuracy and BC. For every 0.1 SG you drop below 1.5 you will have an average of 3% BC loss. This number is better and worse for certain bullets. But for example, if you calculate out to a 1.3 SG then you can expect an average BC loss of 6%. On the other side, over spinning a bullet is a bit of a myth. So if your barrel twist rate is far faster than recommended, you only need to make sure you account for the added spin drift. Also remember the recommended twist rates are for EVERYONE. So shooters at higher altitude, can get away with slower twist rates. Your DA (Density Altitude) plays a role here.
Yes, the stability calculator is accurate for tipped as well as non-tipped bullets.
Nothing is wrong here. A phenomenon called Aerodynamic Jump is causing this. When a direct crosswind makes contact with the bullet as it is leaving the barrel, it causes a slight and permanent shift in the trajectory. This can be seen by setting your wind speed to 0 or setting your wind direction to 12 or 6 o’clock. You will see your zero has returned to your zero range. This is covered in full detail in Applied Ballistics for Long Range Shooting 3rd Edition, Chapter 5.
For a 100 yard zero you DO NOT need to worry about atmospherics. This is for long range zeros (example 300 yards). If you zero at 100 yards, your zero is good for altitudes and conditions.
The biggest culprit here comes from 1 of 4 different places.
- BC: Sometimes users will select to use a G7 BC, or switch BCs but the number doesn’t actually change. Make sure you verify not only that you have selected the correct drag standard (G1 or G7), but that it is an appropriate number. If you are running a 6.5 Creedmoor, and have a BC of around .600 yet you have selected G7 form factor, this is incorrect.
- MV: Sometimes users do not have the correct muzzle velocity input (this can be due to change in weather), but it can also be due to using MV Variation (Or Temp Table) incorrectly. We have detailed information on how to use this feature in the AB Mobile Guide on the User Guides Page. Your input for fps/degree should be between zero and two; any higher and you’re going to be off.
- Turret Tracking: This tends to throw people off for a number of reasons. First off, some users don’t know to even check this. Remember it’s a mechanic adjustment that is subject not only to wear, but defects. Secondly some users don’t know how to input it correctly. If you have the Kestrel, you simply correct your MV for this. You can find out more in the Ballistics Calibration Article in the Articles. If you are using the AB Mobile app, you are entering a correction FACTOR. Meaning that number is going to multiplied by something. So if you change that 1 to a 0, you are in for a world of hurt. The AB Mobile guide on the resource page tells you how to properly use this number, on top of the turret tracking test document you can download which has the formulas and setup for this test.
- Segmented BCs: You should always double check and make sure that the segmented BCs are in order. If they do not follow in order for velocity, it can cause firing solution errors.
You should be using a Custom Drag Model, which is neither a G1 nor a G7. It is actually a representation of the actual bullet model against itself. CDMs (Custom Drag Models) ARE NOT G7 curves or segmented BC’s. However if you are going to use a G1 or G7, use a G1 when it’s a flat base bullet like the 22LR and 40 gr FB Varmint, use a G7 when it’s a boat tailed like the .308 185 gr Juggernaut and .243 105 gr Hybrid.
I have a gain twist barrel, or I plan on getting a gain twist barrel, how do I input this/what twist rate should I get?
The important thing with gain twist is that the muzzle exit twist needs to be the twist required to stabilize the bullet (or faster). So as a ballistics program input, if it’s a 1:10-8” gain, you would use is 8.