20 Shots over LabRadar and Chrony: Comparison.

[Klem]

For those interested in how an old fold-out Chrony compares to the new LabRadar.

I set them both up with the radar beside the gun and the Chrony out front and fired 21 rds to compare. Then entered the average Chrony velocity in JBM to correct it back to muzzle velocity (MV).

The data.



Looks like the MV's are a close 3fp to each other. I am surprised at how similar the results are. I was under the impression the old Chrony with its 5% error compared to the (presumably) more precise 0.1% radar error would have it showing a higher standard deviation (SD). They are almost the same. The SD reflects the quality of the factory ammunition of course but I assumed the SD's would be different, with the Chrony higher than the radar. I also assumed there would be a bigger difference between muzzle velocities...More fool me!

The difference in muzzle velocities is almost negligible. 3fps can be accounted for in angle of the chrony relative to the flight path, or how open and flat the device was. Or how accurately I measured the distance from muzzle to Chrony which wasn't very scientific (paced it out). Maybe the radar is part responsible for the difference. The difference is so low that it's not going to concern any pressure or ballistic calculations you might use it for.

Looks like the old fold-out Chrony is as precise as a LabRadar. Now I have to convince myself the cost was worth it in other ways...


(Footnote. The test was done at night with LED light-strips on the Chrony. I found being able to control the light across the sensors at night gives the most reliable and error-free readings).

[bj139]

Thanks, Klem.
I was not going to set up my Crony to measure velocity when going to the range. I haven't in the last 20 years.
I figured it was too much trouble.
So far, the Labradar is so easy, I will always take it to the range and use it, so cost per use is very low.
I bought a padded laptop case with shoulder strap at Walmart today for $20 which fits the LR well.

[grayfox]

Good work Klem, we need studies like this. I have a magnetospeed and am glad the radar is working for you all, and that the older style works also. Am pleased and have my system for the MgSpd, main thing is to get accurate data so you can figure out how to tweak your loads...
I'm, what to say? agnostic (really, indifferent is probably the word, goes back to an old colleague of mine) on the actual technology used as long as it is accurate.

[Taz575]

I had a Caldwell Chrony, but my dad put 2 shots thru it, so I decided to upgrade. Labradar is so much easier to set up (I use a Primos Tripod so I can move it and adjust the height and stuff to the gun I am shooting; my shooting benches are a bit small. With the new phone app, it makes it very easy!

[Troutguide]

Anyone have a labradar that replaced their chrony, I will take the chrony off your hands. I can deal with negligible differences.

[Double Naught Spy]

Looking closely at the data, all I can determine is that you won't get the same reading for the same shot with the two instruments. Ha!

It sort of bothered me they they were not consistent. By that, the Labradar wasn't always faster than the chrony or vice versa. It was sort of all over the place.

Given the price difference, I would say the chrony is just fine.

[Klem]

Looking closely at the data, all I can determine is that you won't get the same reading for the same shot with the two instruments. Ha!

It sort of bothered me they they were not consistent. By that, the Labradar wasn't always faster than the chrony or vice versa. It was sort of all over the place.

Given the price difference, I would say the chrony is just fine.

I'm thinking the inconsistency is accounted for by the inbuilt error of both chronographs. Chrony claims a 0.5% error in their manual so the machine displays up to 15fps higher or lower than what it should be. JBM calculates a 12fps drop between the two devices. The potential error (15fps) is greater than the drop in velocity between chronographs (12fps). That would account for the Chrony not being lower in every shot.

I agree however, over a string of shots both devices were practically identical in precision. For shorter strings, say 3 shots then the device with the lower inbuilt error will be more accurate.

[Double Naught Spy]

For shorter strings, say 3 shots then the device with the lower inbuilt error will be more accurate.

Maybe you are mixing words here, but if I read what you are saying, then this is not true for any particular 3 shot string. In fact, the chronograph with the greatest error can actually be MORE accurate for any given small sample. That is the nature of small sample sets. It just may not be more accurate more often for any particular 3 shot string (a series of 3 shot strings actually providing a larger sample). That is to say that any small sample set may fall anywhere within the range the calculated error. It is possible that any three shots will cluster tightly and accurately. Of course, they may cluster tightly and further away from the true value. Or, they may not cluster at all and be spread over the range of error. This is why a sufficient sample size is critical when making such assessments.

[Klem]

Maybe you are mixing words here, but if I read what you are saying, then this is not true for any particular 3 shot string. In fact, the chronograph with the greatest error can actually be MORE accurate for any given small sample. That is the nature of small sample sets. It just may not be more accurate more often for any particular 3 shot string (a series of 3 shot strings actually providing a larger sample). That is to say that any small sample set may fall anywhere within the range the calculated error. It is possible that any three shots will cluster tightly and accurately. Of course, they may cluster tightly and further away from the true value. Or, they may not cluster at all and be spread over the range of error. This is why a sufficient sample size is critical when making such assessments.

I don't think we are in disagreement. It stands to reason that larger sample sizes yield more confidence than three-shot strings.

[Kswhitetails]

Agreed. Klem, your new assignment should you choose to accept it is a repeat of the above tests at 1000 shot strings. >

I wonder if you could do both tests simultaneously, or if the physical chrony in the bullet path would hamper the radar's effective readings?

[bj139]

Agreed. Klem, your new assignment should you choose to accept it is a repeat of the above tests at 1000 shot strings. >

I wonder if you could do both tests simultaneously, or if the physical chrony in the bullet path would hamper the radar's effective readings?

I think they were done simultaneously, judging from Klem's description.

[mdewitt71]

I have the ProChrono Didgital, the Caldwell, an AlphaMaster and the LabRadar and I am within 3-4 FPS of all of them.
I get the best SDs from the ProChrono and the LabRadar for sure.
Anymore these days I am only using the LabRadar for guns and keep the other Systems for Archery and Pellets.

[Klem]

Agreed. Klem, your new assignment should you choose to accept it is a repeat of the above tests at 1000 shot strings. >

I wonder if you could do both tests simultaneously, or if the physical chrony in the bullet path would hamper the radar's effective readings?

I did... One bullet, two readings.

[bj139]

Klem,
I shot some American Gunner today and got the following readings.
The standard deviation is significantly less than yours at 43. I wonder why?

And Federal 223 even better.

Hornady American Gunner 6.5 Grendel

[Klem]

Klem,
I shot some American Gunner today and got the following readings.
The standard deviation is significantly less than yours at 43. I wonder why?

Different ammo yields different variances. Mine was Aussie Outback 55gn SMK factory in .223. Careful handloading yields lower SD's, hopefully in the single digits.