Things that cause inaccuracies on the FX Chronograph - Experiments and Results

[SkeeterHawk]

Some of my conversations with @Ballisticboy have been enlightening and made me want to experiment with the FX Chronograph to see what causes it to give erroneous results. I did three shots each with each of the 21 experiments to see what makes the Chronograph read incorrectly. Here are the basic results:

Here is some pictures of how I did the tests:
Test #1 - Baseline - 1/4" below the moderator and even with the muzzle:

Here is test #2 with the Chronograph pulled toward the gun by 2":

Here is test #3 with the Chronograph pulled back 8":

Here is test #4, where the Chronograph is moved 2" away from the Muzzle:

Here is test #5, where the Chronograph is 8" away from the Muzzle:

Here is Test #6, where the Chronograph is 2" below the barrel:

This is test #7 is where the Chronograph is 8" below the barrel:

Here is test #8, that is supposed to be about 6 degrees, but is actually about 8 degrees:

Here is test #9, where the Chronograph is facing down by 11 Degrees, but in this experiment, we are closer to 14 Degrees:

This is test #10, where we are angled downward by about 23 degrees:

Test #11 is where we are angled down by 45 degrees. This is actually about 43 degrees:

It turned out that it was facing the table, so I wasn't that hopeful that I was going to get a reading. I didn't, but here is how it looked for the first shot:

I moved it out to the edge for the next two shots, and it didn't read any of them:

This is Test #12, where the Chronograph is facing 6 degrees to the right:

Here is Test #13, where the Chronograph is facing 11 degrees to the right:

Here is Test #14, where the Chronograph is turned 23 Degrees to the right:

Here is Test #15, where the Chronograph is facing 45 degrees to the right:

For Tests 16-19, the setup looked like this. I used a REALLY BIG piece of cardboard to make sure that I wasn't passing "reflections" around the side:

Something else to note about this picture is that I put boards under the back side of the step-ladder so that the plane of the target was as close to 90 degrees to the muzzle as possible.

Finally, my last couple tests were like this, with the box covering the end of the barrel while I was testing:

I was rather surprised by the consistency of these results. Obviously when it gets off by 45 degrees, it stops working, but that is to be expected. I must say that I was surprised that it was able to read sometimes when the cardboard was only 3" from the muzzle. What are your thoughts about the results of this experiment??

Cheers!

Jonathan

 

[thomasair]

The FX chrono has caused me so many customer phone calls about wild velocity spreads its ridiculous. Lol

Once they try a different chrono….the gun just fixes itself.

Weird

 

[thomasair]

Btw…I’m on my way to bed so I didn’t read through your data. Could you summarize what you think it’s troubles are based on your testing?

Mike

 

[Max B.]

Wow.....when you test something, you REALLY test it. Great job. But the question is, would you buy it again if you lost this one?

 

[Triggers and 4X4s]

Can you add a baseline by removing the zero results and add a total average line for your Min, Max and Average results.

Then sort the results as a mean/median of the baseline.

 

[SkeeterHawk]

Can you add a baseline by removing the zero results and add a total average line for your Min, Max and Average results.

Then sort the results as a mean/median of the baseline.

I'll get on that right away, Heinrich, Sir

you REALLY test it. Great job

Thanks so much! My background is in analytical engineering.

But the question is, would you buy it again if you lost this one?

That is a really good question! I have recently been looking at getting a Caldwell to use as a reference and may just get one of the cheaper ones that @iAMzehTOASTY1 just mentioned on a post as the Caldwell don't seem to be in stock anywhere. Though LabRadar aren't available either, if they were, I assume that they would have the same issues as the FX Chronograph...though the immediate BC would be great. I don't know that much about them, but have heard a lot of people saying that they sold theirs, so I would jump into this purchase cautiously.

Could you summarize what you think it’s troubles are based on your testing?

It's always great to hear from you, Mike! I haven't scrutinized the data that much yet. I wish I would have had more shots per data point, so I may have to reconduct part of this. The most obvious thing is that when you introduce an angle in whatever axis there are more errors, just as @Ballisticboy has been pointing out. The other thing that obviously introduced errors that weren't really reported in my post were the blast of air disrupting the Chrony when it was 8" from the end of the muzzle. I had to throw out a few of those because it was obvious the air was screwing up the Chrony. This is the reason why I never attach my Chrony to my barrel any more as I always got inconsistent results when trying to hang it off the moderator. Once I stopped that, my results are MUCH more consistent, so I didn't do any of these tests with the Chrony touching the barrel at all. Perhaps you should first suggest that your customers not use the rubber bands...and then get a new Chrony if necessary. The final observation that I have is that it seems that (for the most part) that the errors will lead the reading to go high when something is mis-aligned. I may need to reassess this.

Cheers!

Jonathan

 

[huntr]

I just read a post on another forum by Ballisticboy and the statements didn't make any sense to me. Then I come over here and there is another thread about radar chronographs... FX in particular.

I've owned my FX Pocket Chrony for more than two years and have had very few problems. About the only consistent problem... and it's not a rampant problem... is that it will occasionally disconnect from Bluetooth and fail to give a result to my phone. I attribute that to the fact that I'm shooting in my basement and the WiFi signal may have something to do with it.

Back to addressing the OP's testing.

I am not a chronograph or radar expert, but I'm not surprised that there was no reading from the 45⁰ test. The projectile did not pass through the radar beam cone. Other than that, the readings were pretty consistent considering the off angles and pellet and gun variations.

I mostly record velocities indoors in my basement for convenience sake, but I have used it outdoors on the range. The convenience of shooting indoors means I don't need to hang the chrony from the gun. I can sit it on top of a tripod which allows me to move the gun without getting an unwanted reading. This is especially handy with springers or multi pump guns.

I hang the chrony from the gun when I'm on the outdoor range. First, because I don't usually take the tripod with me, and second, it would be unsafe to walk in front of the bench if there was anyone else on the range.

My chrony is usually sitting even with or behind the muzzle, and from less than an inch to maybe two or three inches below the gun. Occasionally it has been slightly forward of the muzzle, but I don't think more than an inch or so. I've used it with and without moderators, Calibers from .177 to .30, CO2 and air, velocities from the 300's to just over 1100 fps.

I recently received a LabRadar chronograph, but I have not been able to get it to work well with the airgun trigger setup. I'm getting low readings. Haven't messed with it very much so I just haven't figured out what I'm doing wrong, yet.

 

[Trucker3573]

I don’t think the chrono is erroneous or bad in itself at all. When the pellet leaves the barrel it decelerates fast. The speed all depends how far the projectile is out of the muzzle. The placement of the chrono determines where the radar signal it emits picks up the projectile shot. The further it picks up the projectile from the barrel the slower the speed will be. I noticed the discrepancies in speed vs placement right away with mine. Thought this thing is junk. Then I thought about it and what I typed above hit me. Radar is very accurate and the fx chrono is fine. If you want muzzle velocity mount it right below the end of the barrel.

 

[Ballisticboy]

The thing to remember with radar chronographs is that they do not "measure" muzzle velocity, they measure a series of velocities down range and then work back to what the velocity was when the pellet was at the radar. The radar does not know or care where the rifle barrel is. The velocity the radar calculates is going to be dependent on the amount of data it manages to collect, how far away the pellet is at the first data point, and the angle between the radar line of sight and the pellet trajectory. The problem with the FX is that you have no idea how much real data the estimated muzzle velocity is based on or where that data started.

The results are all interesting. I have not studied them all yet. It may be worth carrying out an experiment to see how the measured velocity varies with the radar in its usual position over a similar number of shots to the total fired in the experiment. Time-consuming, I know, but there is no substitute for basic data to give a baseline.

As for the LabRadar giving an instant BC value, unless you can input the atmospheric data into the radar, along with the correct reference drag law for pellets or slugs, the answers will only be a very rough guide. But, in the end, it all depends on how accurate an answer is needed, for many people only wanting to know out of interest, or only calculating trajectories to a maximum of 50 yards, a rough guide may be perfectly adequate.

 

[Privateer]

LabRadar was to complicated for me so I traded it off.

 

[SkeeterHawk]

I've owned my FX Pocket Chrony for more than two years and have had very few problems.

I stopped having problems after I stopped trying to hang it from the barrel. My readings got much more consistent when I did that.

I recently received a LabRadar chronograph, but I have not been able to get it to work well with the airgun trigger setup. I'm getting low readings. Haven't messed with it very much so I just haven't figured out what I'm doing wrong, yet.

I have heard that a lot. @AEAC (Steve) seems to get good results from his, but a number of people like @Privateer got rid of theirs.

I don’t think the chrono is erroneous or bad in itself at all.

I agree, you can't beat the convenience, but it has some idiosyncrasies.

When the pellet leaves the barrel it decelerates fast.

Again, I agree and proved that the FX Chronograph will measure it in this thread shooting toward the FX Chronograph

The velocity the radar calculates is going to be dependent on the amount of data it manages to collect, how far away the pellet is at the first data point, and the angle between the radar line of sight and the pellet trajectory. The problem with the FX is that you have no idea how much real data the estimated muzzle velocity is based on or where that data started.

I was surprised that the FX Chronograph was able to read with the cardboard just 6" away from the muzzle. At 3" away, it seemed to need to be exactly square to the cardboard to get a reading...but it did, which surprised me.

It may be worth carrying out an experiment to see how the measured velocity varies with the radar in its usual position over a similar number of shots to the total fired in the experiment. Time-consuming, I know, but there is no substitute for basic data to give a baseline.

Yea, it would be good to have better data. I was particularly bummed that my first test (baseline) had a spread of 14FPS. I would normally throw that low reading out and shoot again, but this was an experiment, and I was only giving each test three shots each. I was trying to get a general idea of where you needed to be careful if wanting to get the most reliable data. Ideally, I would like to shoot 6 shots on each test and throw out the farthest out-liar.

I pretty much got the information that I was after ultimately, and that was that the readings are pretty consistent as long as you are reasonably careful to get the radar on the same plane as the shot. I haven't scrutinized the data yet either, but anecdotally it appeared that introducing an angle gave more variance than the distance from the muzzle did. I am thinking about getting one of the cheap opto-chronies to use as a reference and do some of these again.

 

[HogKiller]

I was rather surprised by the consistency of these results. Obviously when it gets off by 45 degrees, it stops working, but that is to be expected. I must say that I was surprised that it was able to read sometimes when the cardboard was only 3" from the muzzle. What are your thoughts about the results of this experiment??

Cheers!

Jonathan

Thank you for this, it confirmed my own SOP testing, the FX wants to be back from the muzzle, I run it at 6" back, been pretty reliable. It probably falls into the cone faster 6 - 8" back.

 

[Enkey]

I just read a post on another forum by Ballisticboy and the statements didn't make any sense to me. Then I come over here and there is another thread about radar chronographs... FX in particular.

I've owned my FX Pocket Chrony for more than two years and have had very few problems. About the only consistent problem... and it's not a rampant problem... is that it will occasionally disconnect from Bluetooth and fail to give a result to my phone. I attribute that to the fact that I'm shooting in my basement and the WiFi signal may have something to do with it.

Back to addressing the OP's testing.

I am not a chronograph or radar expert, but I'm not surprised that there was no reading from the 45⁰ test. The projectile did not pass through the radar beam cone. Other than that, the readings were pretty consistent considering the off angles and pellet and gun variations.

I mostly record velocities indoors in my basement for convenience sake, but I have used it outdoors on the range. The convenience of shooting indoors means I don't need to hang the chrony from the gun. I can sit it on top of a tripod which allows me to move the gun without getting an unwanted reading. This is especially handy with springers or multi pump guns.

I hang the chrony from the gun when I'm on the outdoor range. First, because I don't usually take the tripod with me, and second, it would be unsafe to walk in front of the bench if there was anyone else on the range.

My chrony is usually sitting even with or behind the muzzle, and from less than an inch to maybe two or three inches below the gun. Occasionally it has been slightly forward of the muzzle, but I don't think more than an inch or so. I've used it with and without moderators, Calibers from .177 to .30, CO2 and air, velocities from the 300's to just over 1100 fps.

I recently received a LabRadar chronograph, but I have not been able to get it to work well with the airgun trigger setup. I'm getting low readings. Haven't messed with it very much so I just haven't figured out what I'm doing wrong, yet.

Hi
I don't know if it's the same problem, I shoot outdoors and sometimes it stops reading shots and I have more than 50% battery. Anyone else experience this error or know how to fix it. It is the latest model.
Regards
Enkey

 

[huntr]

Hi
I don't know if it's the same problem, I shoot outdoors and sometimes it stops reading shots and I have more than 50% battery. Anyone else experience this error or know how to fix it. It is the latest model.
Regards
Enkey

Are you speaking about the FX Chrony or LabRadar?

When my FX stops recording shots, it’s almost always because it lost the Bluetooth connection. I turn Bluetooth off then back on and the chrony reconnects. It’s annoying, but just one of those things.

 

[Enkey]

Ok. Thanks
Fx chrony

 

[fiske]

Thank you for this, it confirmed my own SOP testing, the FX wants to be back from the muzzle, I run it at 6" back, been pretty reliable. It probably falls into the cone faster 6 - 8" back.

Exactly right.
Pocket Chronograph Manual

 

[Smitty911]

Depending on how each sensor is placed into the unit will determine the slight angles that the beam exits. You could probably spend a great deal of effort find that point. Ex. Say the Beam Center is 2º up and 5º right, so you'd have to make a mount to compensate. That than figure out the beam spread and Place your target in the center for maximum "potential" accuracy. Then go get the Caldwell. Full Disclosure - I have a Lab Radar.
Smitty

 

[Revoman]

Many times if you chrony for a while, then switch it off, it remains 'open' in the background of your phone. When opening the app up again, it is highly likely that it will not record every, or any, shots. I found that if you swipe the app off the screen (closing it), then reopening the app, it works just fine.
mike

 

[SkeeterHawk]

it is highly likely that it will not record every, or any, shots

I have also found this to be true, and when it starts to "lose it's mind", I find it is better to "force stop" the application from Settings and then reopen it. I have never had an issue with it reconnecting using this method. If you try to keep shooting, it seems to progressively get worse at recording shots. Once it misses one, I just reboot it and have been pretty successful doing so. Just my $0.02

 

[Enkey]

So it's possible that the problem is in the application, not in the chrony.