Indoor Chrono Use

[mont1120]

I had been using my Caldwell Pro inside of a rather dark indoor range for a few years, and being a noob at chrono readings I kept getting inconsistent info. I finally broke down and understood the accessory lighting panels were needed, and immediately they proved to be worth every penny. I have been told that florescent indoor lights can cause erroneous readings if they are close to the chrono.  

 

Is it really a requirement to built a box to place the chrono inside of to get the true readings from the setup? The infrared strips seem to be working fine, and I would like to perform testing outside also. Since all the big matches use a box to cover the chrono setup, is this the only way to gather true readings?

 

As a side note, at the big match yesterday, my .45 230 grain loads measured 745, 738, and the last one was 698.5............made major fine but what a surprise. The rounds were MG round nose with 3.8 grains of Nitro 100. How I got a 698 is a mystery.

[Braxton1]

"Chrono Coffins" are used to exclude extraneous light from the sensors.  It ensures that the sun (or in your case, those pesky fluorescent lights) don't affect the setup.

 

You're only looking at a 3 round sample.  That is too small to get any worthwhile data.  When I am testing new loads, I will do 10-20 round strings.  If I had 9 rounds like the 745/738 ones and one that was 698, I wouldn't worry about it at all.  However, with a large sample size, you can get a true Standard Deviation.

 

A 47 fps extreme spread wouldn't be too bad for regular ol' blasting ammo.  If you're using range pickup brass, there can be enough of a variation in case length to cause inconsistency in your crimp.  Inconsistency there can cause big swings in pressures and subsequent velocity spreads.  If this was with headstamp-sorted brass of known source, I'd be looking to experiment with other powders....

[jschweg]

You may or may not be interested in buying yet another Chrono, but the new version of the Caldwell (g2) is flipped upside down with the sensor on the top and a light kit on the bottom. It works perfectly indoors under florescent lighting without needing to build a box.

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[jwhittin]

Braxton is on the right track. You can't get consistent velocity results using only 3 samples. What you need to pay attention to is your measured standard deviation. But you only need 8 samples to get a valid estimate.  Then add at least 2 times your STD to the velocity needed to make PF. This gives you your desired avg load velocity. This ensures at least a 90% chance of passing the chrono check in the first 3 rounds. 2.5*STD gives you 95%, 3*STD corresponds to 97%. 

 

So if you STD is say 15fps, you want your average velocity to be at least 718+30=748fps measured using 8 rounds. 

 

Make sense?

Edited November 4, 2017 by jwhittin

[Hi-Power Jack]

I fire 20 rounds over the Chrono, and want ALL 20 to make PF.

 

That makes me 100% chance of passing the chrono check     

[jwhittin]

Not 100%, just a high probability.  As I have mentioned, using more than 8 to 10 rounds to measure is a waste.  Try it. Record STD and Avg Velocity using 10 and 20 rounds. No difference down to one decimal point.

 

With your approach you end up much hotter than needed.  This is a kin to using the ES instead of the STD. So you could end up at 4, 5, or even 6 times the STD. At 3STD you are already at  97%. 

 

Just trying to save you some ammo and make you a better shooter ?

Edited November 4, 2017 by jwhittin

[Guy Neill]

Nice to know.  I had been considering turning the chrono over for a while, but had not actually tried it.  I did not know anyone was offering one already turned over.

 

My basis was some years ago using a chrono indoors with my lights shining on the floor - and it worked well.  With that experience and knowing the sensors need to be in shadow when outdoors, it seemed turning them upside down might accomplish good things.

 

Guy

 

 

On 10/21/2017 at 5:49 AM, jschweg said:

You may or may not be interested in buying yet another Chrono, but the new version of the Caldwell (g2) is flipped upside down with the sensor on the top and a light kit on the bottom. It works perfectly indoors under florescent lighting without needing to build a box.

Sent from my Nexus 10 using Tapatalk
 

 

[Hi-Power Jack]

9 hours ago, jwhittin said:

 

Just trying to  make you a better shooter ?

 

I've been trying to do that for 65 years ....   

[MikeBurgess]

Nice to know.  I had been considering turning the chrono over for a while, but had not actually tried it.  I did not know anyone was offering one already turned over.
 
My basis was some years ago using a chrono indoors with my lights shining on the floor - and it worked well.  With that experience and knowing the sensors need to be in shadow when outdoors, it seemed turning them upside down might accomplish good things.
 
Guy
 
 
 

I have been known to tip them on their side so the sensors are not in direct sun when it's bright out, I also found that works when it's too dark out.

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[R1_Demon]

Mike - Interesting...I never thought about trying it on its side.  Hmmm...

 

Oh and for those curious on the G2, here is the link to the info on it:  https://www.btibrands.com/product/ballistic-precision-chronograph-g2/ 

 

I happened to just buy the normal Ballistic Precision Kit (with the tripod and lit bars and all that jazz) for a great price before seeing the G2 or I would have said the heck with it and tried that instead, but I can't complain about my normal one.  It works very well.  I have even used it with my crossbow arrows to measure that and dial them in.  Like I said, it works well with a multitude of uses.   

[rottdogsparky]

Mike - Interesting...I never thought about trying it on its side.  Hmmm...
 
Oh and for those curious on the G2, here is the link to the info on it:  https://www.btibrands.com/product/ballistic-precision-chronograph-g2/ 
 
I happened to just buy the normal Ballistic Precision Kit (with the tripod and lit bars and all that jazz) for a great price before seeing the G2 or I would have said the heck with it and tried that instead, but I can't complain about my normal one.  It works very well.  I have even used it with my crossbow arrows to measure that and dial them in.  Like I said, it works well with a multitude of uses.  [emoji4] 

Recently used my Chronograph indoors and had problems with the florescent lights fixed by the light kit, then still had problems so shut off florescent lights put on the incandescent and again worked until I shot 357 hot loads and got a ton of errors thinking it was the propellant reaching the Chronograph before the bullet so going to try the front entrance of the coffin to see if that works.

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[mont1120]

Adding to the discussion, the box seems to be the key. Depending on what firing lane I set the chrono up, it appears the readings are different. I tested a chrono with a good friend, and he had the box on it, which stabilized the readings quite well. Since I shoot range brass at matches, I test the chrono loads the same way. I know there will be greater variations due to brass construction being different, but it tells me pass or not pass.

 

As a side note, the same guy broke his chrono, and he bought a brand new one. We met at the range, and as we were checking the new gear, I watched a shot remove a sizable portion of the top of the chrono. I cannot tell you how bad I felt for him, it is now a decorative lamp holder. With all of the good (and bad) natured ribbing and joking us shooters pile on each other, I could not bring myself to say even one tiny little joke.

 

He shall remain unidentified, but you know the shooting gods are out for you when this happens.

[coolcw1987]

On 11/4/2017 at 11:33 PM, MikeBurgess said:

I have been known to tip them on their side so the sensors are not in direct sun when it's bright out, I also found that works when it's too dark out.

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Are you using the head light off your car as a replacement for the sun? I guess it would be constant just never thought it would work.

[MikeBurgess]

2 hours ago, coolcw1987 said:

Are you using the head light off your car as a replacement for the sun? I guess it would be constant just never thought it would work.

Yes,

and it worked surprisingly well, there was not enough light left to use the sun so I tried this on a whim and bingo nice consistent readings 

 

 

[coolcw1987]

Thats awesome. Ive been there and not had enough light before next time im make sure i try using my truck.