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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
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 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 19 feet to my desired standing location, where there is a nice spot to set the phone.
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 19 feet. My Android phone is right next to the gun muzzle, so that setting is 0 feet. And my Android phone is about 2.2 feet away from the gun, so that's the setting for "Device to Pellet Path".
I found the soft ambient volume to be the best setting for my garage. But you can't figure that out until you actually use it with your airsoft gun.
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.
So the first airsoft gun I tested with the Chrono Connect Mobile Lite is my APS Mini Patriot M4, which was the gun I wanted to improve. But surprisingly, the app reported an average of 590 FPS! Needless to say, I was rather shocked. I was about ready to uninstall this app, but I decided to try this app with my other two guns (see later sections for details).
Another surprise to me was that the app report velocity correctly for my other two guns. So I decided to play with the settings. It turned out the APS Mini Patriot M4 required the "De-Bounce Effect" setting to be set to "Mild". The screen shot below shows the possible "De-Bounce Effect" settings.
When the "De-Bouncing Effect" setting was set to "Strong" or "Very Strong", the velocity calculation was too low. When it is set to "Mild", the speed read average of 250 FPS as shown in the screen shot below. That value is 10 FPS lower than the chrono at the indoor CQB arena, but is sufficiently accurate for my needs.
When Chrono Connect Mobile Lite reported speed too high on my HPEG, I decided to try it with 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 the same indoor CQB arena.
Chrono Connect Mobile Lite reported its speed quite accurate. It averaged about 125 FPS with "De-Bounce Effect" set to "None". After increasing "De-Bounce Effect" to "Mild", the reading averaged 117 FPS, which was still sufficiently accurate. So I decided to use "Mild" with all my guns.
It seems that Chrono Connect Mobile Lite has trouble hearing the paper puncture with airsoft guns that shoots slower than 150 FPS. Either that or the Cyma CM023's gearbox is too quiet for pick-up. Because half the time, Chrono Connect Mobile Lite display "-Err-" indicating that it could not calculate the speed and power correctly. It has apparently hear the shot and the hit. Adjusting the volume sensitivity hasn't helped.
My HPEG and my spring pistol were both louder at firing and at hitting the paper target. So I suspect it is the noise level that prevents proper detection for the Cyma CM023.
I have also tested Chrono Connect Mobile Lite with my 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.
Chrono Connect Mobile Lite was quite reasonable with the velocity of this pistol. It averaged about 160 FPS with "De-Bounce Effect" set to "None". When I changed "De-Bounce Effect" to "Mild", the average FPS was 150 FPS. I felt using the "Mild" setting was sufficient for my needs. Especially in this case when I don't know the real velocity of this gun.
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