260. That's the number shown on the chronograph at the local indoor CQB arena tonight for my APS Mini Patriot M4. But the airsoft gun has shot at 330 feet-per-second (FPS) just two weeks before. And the gun has been newly built last month. That's a drastic FPS drop for an airsoft gun. What happened?
I'm obsessed to find out where the air is leaking. But before I can rebuild the gun, I need a chronograph; I need to be able to see the increase/decrease in FPS as I make changes. The most inexpensive chronograph is the Soft Air Swiss Arms BB Chronograph for around $40 on Amazon. However, I think I can do better than that.
I already have an Android phone. It could do almost anything, except cooking dinner. How can I make it a free chrono as well? That's where Chrono Connect Mobile Lite comes in the picture. It's a free Android app that is available on Google Play. You use it as a chronograph. So let's see how well it works.
The basic theory for the Chrono Connect Mobile Lite is to monitor the sound based on know distances and calculate the BB speed. That means you have to set up an audible target at a certain distance to the muzzle of your airsoft gun, while placing your Android phone close by (so you can read the velocity).
I am an engineer, so I believe the theory is sound (not sure if pun is intended). But in practice, feasibility depends a lot of the equipment and the environment. For example, the microphone sensitivity or the echoing of the walls.
Chrono Connect Mobile Lite does not work with all Android phones. It works with my Google Samsung Galaxy Nexus, but it does not work with my Samsung Intercept. Every time I fire while monitoring the shot with Samsung Intercept, Chrono Connect Monitor Lite detects the shot but produces "-Er-" in the output. It's not clear why the app works on one phone and not the other.
But even though Chrono Connect Mobile Lite technically works on the Google Samsung Galaxy Nexus phone--it produces results--the results are incorrect and unreliable. For example, dry firing the airsoft gun produces reasonable, but absolutely incorrect (obviously), results! I don't know if it is the phone, the environment, or Chrono Connect Mobile Lite.
Finally, I was only able to get reliable and precise results using my Motorola XOOM tablet. It's big screen allows me to see the results from long distance. That's especially useful because I find the best position for the XOOM is further from the gun and closer to the BB trap.
I had made my own BB target trap several weeks ago. It makes shooting inside my garage or my backyard a breeze. It has a paper front, which makes a decently loud sound when the BB penetrates it. It seems perfect for the job. Being useable inside my three car garage allows me to chronograph at any time.
Chrono Connect Mobile Light explains how to set up the range within its app (see screen shot below). You can get to that screen by launching the app, pressing the menu button, select "Target Options", then select "Distance Measuring Help."
Chrono Connect Mobile Light requires that the target from the gun is, at a minimum, 15 feet apart. I placed the target trap on top of a car (my eye level) and measured 20 feet to my desired standing location, where there is a nice spot to set the phone.
The actual placement of the Android device to the airsoft gun and the BB target trap requires a lot of trial-and-error. My Google Samsung Galaxy Nexus phone would not provide any useable results anywhere in the environment. The Motorola XOOM tablet, on the other hand, produced excellent results five feet away from the trajectory path, two feet in front of the BB trap, and eighteen feet away from the gun. The gun makes a difference, too. In this set-up, it was able to measure two of my high-powered AEG with precise velocity. It could not measure my lower-powered AEG nor my spring pistol.
The first time I used Chrono Connect Mobile Lite, I had the target 19 feet away, the Android phone 2 feet from the gun. Chrono Connect Mobile Lite measured all three of my airsoft guns--HPEG, LPEG, and spring pistol--with very reasonable results (close to what the chrono at the local indoor field measured). So I was very happy with the set-up. But one day, I accidentally dry fired with the gun and Chrono Connect Mobile Lite still provided reasonable result! I was flabbergasted that Chrono Connect Mobile Lite provided results so close to the real velocity. Obviously, the measurements are all wrong. I wasn't thorough enough at setting up the range and test it with dry firing.
During the trial-and-error, be sure to test with dry fire. While dry firing, you should make sure the Chrono Connect Mobile Lite read back "-Er-" meaning that it could not provide a reading. If it provides a reading when you dry fire, you need to either change its options or change your physical placement or change your environment or change all three. Once you make sure it fails to measure dry fire, try it with BB's. If you have a gun that has been recently measured at a field, then use that to be sure the setup is good.
If you can't get Chrono Connect Mobile Lite to show "-Er-" when you dry fire, at least make sure it reads back a value that is way off from the actual velocity of your airsoft gun. For example, if your airsoft gun measures 260 FPS at your local field and Chrono Connect Mobile Lite measure 350 when you dry fire, then you have a chance. Try measuring the BB velocity with Chrono Connect Mobile Lite. If it reads close to 260 FPS when you fire a BB, then the set-up is good.
Once you have sat-up the range, it's time to set up the Chrono Connect Mobile Lite. It has numerous settings and all of them has to be right to give you accurate reading. The main setting menu is shown in the screen shot below.
The "Target Options", see screen shot below, is where you set the data for your physical range. In my case, I used "Feet" as my units. The "Muzzle to Target" is 20 feet. The "Device to Muzzle", which indicates how far the Android device is from the gun, is 18 feet. And my Android tablet is 5 feet away from the path, so that's the setting for "Device to Pellet Path". I found the "Very loud ambient volume" to be the best setting for my garage and the two APS AEG's I was using.
Next, you need to set-up the ammunition type in the "Projectile Info" settings (see screen shot below). The "Name" setting is not important. And most people, including myself, use grams as the "Weight Units" for my BB's. I use the 0.2 gram BB's, so that's what I put into "Weight".
The "Pellet Shape" is the most difficult entry to fill in. You can choose from "Domed/Pointed (0.025 BC)", "Flat/Hollow (0.015 BC), and "Custom (Enter BC Below)". The app has a link to take you to the Chrono Connect Pellet List. However, the list did not provide data for the two BB's I use--Crosman Biodegradable and Evike Professional Grade. So I decided to stick to "Domed/Pointed (0.025 BC)".
The "Speed and Power Options", see screen shot below, allows you to change the unit for speed and power. However, it defaults to FPS and joules, which are pretty much standard for the airsoft sport in United States. So I didn't have to change anything in that menu.
The "Gun Specific Options", see screen shot below, is meant for spring and gas powered guns. So I do not think I need to set anything. The de-bounce effect defaults to "None".
When you launch Chrono Connect Mobile Lite, it immediately takes you to the chronograph. A "Start Monitoring" button at the bottom of the chronograph starts the sound detection. It will calculate up to three shots before turning the button off. The pro version of the app removes this limitation.
Chrono Connect Mobile Lite keeps your Android phone awake (stays on). That's really handy to watch your speed and power measurements. But remember to shut down the app when you are done so that you don't drain your phone battery.
So the first airsoft gun I tested with the Chrono Connect Mobile Lite are my APS ASR106 Mini Patriot M4 and my Shark Raptor (see how I built this gun elsewhere on this web site). These two guns are my bread-and-butter HPEG. They are both louder than my Cyma MP5 LPEG and my Colt 1911 spring pistol. The Shark Raptor is much louder than the APS ASR106, due to the pistol inner barrel I put into the rifle.
These two guns had been measured at the local indoor field recently, so I know their velocity. Chrono Connect Mobile Lite was able to get the velocity pretty much spot on with the settings I mentioned earlier.
I tried Chrono Connect my Cyma CM023 MP5 rifle. It was a LPEG that shoots 130 FPS in many video reviews. In fact, it measured 130 FPS two weeks ago at my local indoor CQB arena. The LPEG is very quiet. And its low speed made a smaller sound on the BB trap as well. Chrono Connect Mobile Lite had trouble hearing the sounds even on the most sensitive setting. It reported "-Er-" almost every time. It might be possible to measure this gun if I made drastic changes to the range. But after setting up the range for the HPEG's, I was reluctantly to change it.
I have also tested Chrono Connect Mobile Lite with my Colt 1911 Target spring pistol. I have never chrono'ed this pistol. However, the specification says it has a maximum energy of 0.3 joules. If you use the BB Pellet Energy Converter, you'll see that 0.3 joules with 0.2 gram BB's translates to 179.7 FPS. I was also unable to get good readings with Chrono Connect Mobile Lite with this pistol. The firing is a loud snap, which Chrono Connect Mobile Lite could hear clearly. But it's low speed also doesn't make much sound on the BB trap. I was also reluctant at changing the range to meet the requirement for this gun.
It seems every gun requires a different set of app setting. The physical set-up may also need to change. As I mentioned before, whether Chrono Connect Mobile Lite will work depends on your equipment and environment.
I was able to get it to work with my two APS M4 AEG in my garage. However, I could not get it to work with my Cyma MP5 LPEG and my Colt 1911 spring pistol.