Chronograph - minimum distance from muzzle?

I have Caldwell Ballistic Precision Chronograph Premium Kit which I bought some time ago, but am only now finding time to use it.

I was considering to mount the Chronograph on a board together with a Pistolero rest so that I can conveniently transport the complete rig to the range and then the clamp the board to the fixed range bench. I was hoping that the board could be no more than 4 feet long - chrono at one end - rest at the other. So the distance from muzzle to chrono would be about 30".

I see in the instruction sheet that Caldwell recommend positioning the chrono 10 to 15 feet from the gun. That does not work well at my local range. I assume that they specify that distance in order to avoid muzzle blast from damaging the chrono (they say one arrow length for bows).

What is the absolute minimum distance from gun muzzle to chrono that will work? I will be testing various target pistols from 22LR to 45ACP, with the usual Bullseye mostly sub-sonic ammo.

10 feet.

The shock wave can trip the crono when it’s too close.   It will give incorrect readings.  I use 15 feet. 

David

Mine has a remote display/control head that is separated from the unit itself with a 12 foot cord, so I assumed that  there was a reason for that and use it at that distance!

What they said....

You might want to check out Labradar. They are positioned next to the muzzle, very convenient particularly at an indoor range. 

https://mylabradar.com/

Yes, that Labradar is really cool - but a bit pricey. I will experiment with my cheapo Caldwell first.

I have the same chrono and the same problem at my range. All I can tell you is I use mine on a daily basis and I have it at 3-4 feet and I have never had an issue when the sun is out! Never not one!

OK, I tried my Caldwell at the range today - I was alone and so no problem to go to-fro setting and adjusting.

I did not realise that the tripod that came with the set is actually very capable and can be adjusted to a decent height - good. I tried it at roughly the maximum distance that the connecting cable will go - about 12 feet I guess. The Chrono worked and the display on the front of the unit was clear to read from the bench. I had already downloaded the Android App on my phone, but I could not get any results to display on the phone - never mind, the readout on the unit was good enough for my objective today.

I then moved it close to the bench (close enough that I could lean forward and reach the unit). I tried some 22LR. No good, very inconsistent results, but generally much lower FPS than expected. Moved it back to about 12 feet and tried again with the same ammo. OK, as expected FPS and consistent.

OK, so I now know basically how to use the Chrono and where to put it. No problem on quiet week-day afternoons when I am usually alone on the range anyway. I don't expect (hope!!) to need to use it very often. I will contact Caldwell to try to fix the phone connection issue. But, if I ever get into a situation where I need very frequent and comprehensive velocity testing, the Labradar is probably the way to go. (I wonder if they make a Labradar Retriever? )

Thanks for all the comments and advice from everyone.

I will take a pic or video tomorrow
I did not say “ so close you could touch it” I said 3-4 feet

Yes. I totally understood you. But I wanted to prove for myself whether it would work right up close. Everyone said no and you are all correct. If I cannot mount it on a short board, then 4' or 12' are effectively the same to me as I then have to use the tripod and go out into the range to set up. But it is good to know that your somewhat closer distance also works, there might be occasions in future where that info helps. Thanks.

NRA handgun test chronos are at 10 ft.  I use 5 ft. with no problems with my cheap Pro Chrono.

Use your Caldwell to test this 45 at 3ft. Then you will be in the market for a new one and you can get the Labradar. Ok, not helpful but I see you have your answer.

Len

A pal told me a story about two young dudes with a big magnum revolver who saw some deer on a country road. Rested the gun on the hood and fired. Took all the paint off his brand new custom truck hood.

Caldwell got back to me via email very promptly and efficiently - excellent. Here are some comments from their specialist. I still have not been able to get my phone app working properly - but probably just my lack of "teenager" skills! The chrono does work and the display panel on the front is adequate for my current needs. I've been able to prove that I had a problem with a large batch of reloads - so some useful progress.

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Please try the following steps for troubleshooting the issues with your chronograph G1(corded) or G2(Bluetooth):
Setting up the App
1.    Go into your phones settings and find the Caldwell chronograph app and be sure that all permissions are granted, For the G1 this will include use of the microphone, once the cord is connected turn the volume up on your phone this will help mark sure a good connect is being made with the chronograph.
When in the app hit settings and disable Bluetooth for the G1, enable Bluetooth for the G2.


When Shooting
1.    Always use your sun shades and if you have LEDs on yours use them as well. Both of these will help with creating consistent lighting. You should never shoot while around florescent lighting.
2.    The chronographs work off of creating a shadow and measuring the time between sensor to sensor. So while they will work smaller calibers like those from BB or pellet rifles will be more difficult. Make sure to shoot across the sensors as level and straight as possible at a height of about 1.5-3 inches away.
3.    Shoot from a distances of 10-15ft from the front of the chronograph. The larger the load the more muzzle flash there will be and that muzzle flash can have effect on the readings.