Chronograph problems

[AK Eggy]

I have a Beta model that I had some trouble with this weekend. It was only the 2nd time I’ve used it (bought it new)…the first time it worked great. This time, the readings I was getting were extremely low. I was shooting a .45 ACP and measure velocities between 170 and 211 fps. It was consistently reading that velocity. I varied the distance to the meter between 10 and 15 feet, I tried with and without the diffusers. No matter what I did, I couldn’t come up with a reasonable piece of data. I also tried a 44 mag. with similar results

It was a clear sunny day with no clouds at all. The first weekend, when it worked as I expected, the conditions were nearly identical and I used the diffusers.

Any idea why my velocities were so low? Where do I start troubleshooting to correct the problem?

Thanks in advance for your help,

 

[lwknight]

There could be a dozen different things affecting your readings.

Some points to consider.

Is the light getting on to the diffusers
Are you too close. Muzzle blast affecting the sensers
No dust or something actually on the sensers.
Gas checks separating from the bullets.
Shooting squarely or should I say straightly across the sensers
Smoke from the muzzle blast
Senser loose in the mount
Low batteries.

Its bedtime so thats all I can think up right now.

 

[Steve C]

Some things that I've seen that will give you strange readings in addition to the above:

Batteries low on charge, diffuser shadow not over the sensors, errant flashes of light flashing off passing automobile windshields, mirrors, or distant lightning. too close, too much smoke from bullet lube. I always take a .22 lr with known velocities to reality check the chrono readings.

 

[loadedround]

I agree with all the above reasons that Mr. Knight stated, but I have found that bright overhead sunlight to be the biggest culprit of all.

 

[NCsmitty]

If your battery is fresh, then the light conditions are causing your errors. It's later in the year, and the sun's angle is changing and is affecting the sensors.

I've been playing around with using a large beach umbrella with just enough coverage to keep direct sunlight off the sensors on a really bright day.
It seems to work well, as without it, I was getting the ERR or crazy numbers.



NCsmitty

 

[USSR]

It was a clear sunny day with no clouds at all.

Ah, yes, BTDT. First thing you will learn, the diffusers are not enough on bright, sunny days. Mount the diffusers, but then tape something between between them and extending off to the sides to make sure no direct sunlight is shining on the sensors.

Don

 

[Asherdan]

Like USSR said, as far as light issues. My solution has been a translucent grocery bag cut open and tape a few inches down the diffuser rods to create a 'white box' background.

lwknight gave a good summary checklist to run through.

 

[jerrard]

Finding the solution to this problem was a real hair puller. Second NCsmitty, beach umbrella proved to be final solution.

 

[TexasShooter59]

I'm still learning how to use my Beta, but it IS getting better!

What they said about the bright sunny day was happening to me. Something I tried last time that worked well, was to remove the diffusers leaving the rods installed, then rotate the Chrony around the horizontal axis that runs from you to the target so that the sensors are actually in the shade of the Chrony.

This is hard to explain without a photo, but imagine you sitting at the bench with the sun at 2 o'clock in the sky. The Chrony is rotated so that the sensors are pointed toward about 10 o'clock. The shadow of the Chrony itself should pass over the sensors.

Leave the rods installed so you know where to shoot - between them as usual.

 

[Flintknapper]

Though lighting is the most likely culprit, don't rule out a problem with the unit itself.

Mine has never recorded velocities under 1,000 fps.... and yesterday it started doing exactly what you described (reading very low...for the cartridge used).

NO attempt at shading the sensors changed anything. It would only show velocities in a very narrow window (1500-1600) regardless of what was shot over it.

Mine is going back to the manufacturer for evaluation.

 

[AK Eggy]

What I tried

The sun was pretty low...coming in at about 9-10:00 from the unit. I tried with and without the diffusers, checked the connection of the cable on both ends.

Now don't laugh!!!!! My friend noticed I had the unit bass ackwards....the back towards me. I thought for sure that was it, but it wasn't. Turned it off and let it set for about 1/2 hour thinking I "confused" it and tried again...still no go.

Anyway, I was thinking it was the angle of the sun so we put up a target stand next to and parrallel with the chronograph to shade the entire unit and that didn't make a difference either.

I think the only thing I didn't look at was the battery as it was a brand new one, but I'll check that next. I'm really wanting to get it working again, I've always ben curious about different velocities.

Thanks for everyone's help...More ideas are always appreciated.

 

[chbrow10]

When there is direct sunlight shining into the sensors, I have experienced what you describe. I am fortunate to have a lot of USPSA targets to practice with. I find that when I am having lots of trouble, I put the target on top of the diffusers with the white side facing the sensors and it seems happier.

You are holding your mouth just right while praying to the chrono gods, right?

 

[USSR]

If you've shaded the sensors and are sure you have a good battery, that's about all you can do. I bought one off of eBay that didn't work correctly, so I sent it in to the manufacturer and had them upgrade it while it was there. Very reasonable and works fine now.

Don

 

[grubbylabs]

Wow this had been a handy read. I have had problems with my chrony as well. Only it is giving high speed for me. For some reason I doubt that my 45 with a 4" barrel is passing my 44 mag with a 4" barrel. I will have try some of your suggestions.

 

[dagger dog]

You may be shooting too high above the sensors, sand bag the firearm and have a buddy hold a tape measure against the barrel, extend the tape to the Chrony 10-12-ft,check that the tape is parralell to the sensors and see if the barrel is too high above or not square to the sensors, it also helps to keep from SHOOTING the CHRONY.

In previous thread someone was putting their Chrony in a translucent plastic box with the diffusers installed, to keep the direct ligh off the sensors.

 

[lwknight]

I seem to have best results when the sun is either behind or in front of me.
For some reason the side sun tends to adversely affect the readings' consistency.
I don't even know what brand I have. It was $99.00 at Callelas.

 

[1SOW]

Chronos are built to work in 'diffused' light. The sun at 12:00 with the diffusers on should work. A cloudy day with no diffusers should work.

Early in the morning or late in the afternoon is a bad time to chrono. The sun can come in 'under' the diffusers and cause bad readings.

Put up a target (red sticky works) behind the 'level' chrono and aim at point level with the gun about half way up the diffuser rods. Adjust the chrono height to set these conditions and it should work. If it doesn't, send it back.

 

[Kernel]

An oldie, but a goodie....

Portable Chronographs - How They Work by John Wootters

Handloader Magazine, March-April, 1972 Vol. 7 - NO. 2, Issue 36

"... photoelectric screens will be triggered by sonic waves under certain conditions, such as firing loads with a relatively high muzzleblast and sub-sonic bullet velocities, such as certain handgun loads. In such cases, a baffle must be used to break up the sound pattern, or the chronograph will simply measure the speed of the sound waves."

Chrony error caused by the muzzleblast's sonic speed shock wave moving faster than the sub-sonic speed bullet.