ProChrono vs. Cauldwell DATA

[mmorris]

I tested these two units today, and I am posting the results here.
This was not scientific or rigorous in method. Just a few 22's over the end-to-end units. I don't know for sure what the ammunition was, I just used what was in the magazines. Could even be mixed.

I did remove these from the list below as erroneous data:
ProChrono Cauldwell (disagreement)
1008 1071 63
1054 1099 45
These were the last two shots in the string.

03/22/16 04:00 PM
Ruger MKIII

ProChrono Cauldwell (disagreement)
1054 1069 15
1042 1058 16
1013 1030 17
1059 1076 17
1004 1020 16
1029 1043 14
1001 1017 16
1049 1067 18
1054 1065 11
1029 1041 12
1031 1045 14
981 994 13
1018 1021 3
1040 1055 15
1064 1073 9
1008 1020 12

 

[ewlyon]

Interesting test. You should try reversing the placement to see if that small distance is a factor, even if it only results in indicating only a couple fps lost between the chronographs. It is encouraging to see that the numbers for both are very close and the disagreement between the two has a small variation.

 

[AnselHazen]

Ok that's cool. Nice knowing these units are supplying believable data.

What's inside the blue barrel?

 

[mmorris]

50 Rounds Both Ways

Here are the results of the Positional Data Test:

The Caldwell data is consistently higher than the ProChrono data for the same shots, regardless of position.

When the Caldwell unit is first in line, the data it reports is 5.4 FPS (avg) HIGHER than the data it reports when it is second in line.

Caldwell 1st Higher by 18.0
Caldwell 2nd Higher by 12.6
Positional difference 5.4

I have attached a pdf of the data spreadsheet with additional info reported.
(I don't know a better file type to attach from excel)

 

[mmorris]

The barrel is just filled with sand.

 

[Toprudder]

That is just a little over 1% variance. Pretty good if you ask me.

 

[Reloadron]

The difference you are seeing in the full scope of things is really not very much all things considered. Looking at a chronograph in general in its simplest terms here is what happens. A projectile crosses the first sensor and in doing so generates a pulse. This is a "start" pulse and think of it as opening a gate. The chronograph has an internal "clock" or oscillator generating pulses. When the start pulse opens a gate the clock pulses are allowed to pass through the gate and be counted. When the projectile passes the second sensor another pulse is generated called a "stop" pulse and this pulse closes the open gate. During the period between the start and stop pulses the clock pulses are counted. The sensors for start and stop are spaced a known distance.

V = D/T
V: Velocity
D: Distance
T: Time

Everything hinges on the clock frequency since the Distance is a given based on the sensor spacing. The time of the clock pulses is the reciprocal of the clock frequency. So F = 1/T and T = 1/F. The internal clocks used in these chronographs are not exactly high grade laboratory instruments. They drift and have an allowable uncertainty. Plus or minus 10 FPS in a 1,000 FPS measurement amounts to about +/- 1.0% so if two units agree within 1.0% or 2.0% it's actually pretty good.

All in all, my guess as to why there is a difference is a difference in each units clock frequency. The sensor distance on these units is a fixed value. Does the difference surprise me? No, not at all.

Ron

 

[Hondo 60]

I'd be willing to bet you'd see the same difference if you put 2 of the same model together like that.

 

[ewlyon]

This is really neat. Thanks for sharing this these test resultss

 

[Blue68f100]

Yes there is a difference between the 2 units but is either one correct?

Both could be off more or less depending on actual value.

In the end these are just tools to help us out.

 

[Reloadron]

Yes there is a difference between the 2 units but is either one correct?

Both could be off more or less depending on actual value.

In the end these are just tools to help us out.

Absolutely. Every chronograph will have an allowable margin of error. So which of the two is closer to being nominal or correct? Beats me and short of really crawling into them we will never know which is the more truthful between the two. Close enough!

Ron

 

[mmorris]

Considering the price these sell for, I am surprised to see so little difference on average.

I think that these tools are for us to make judgments on how our firearm/ammunition performance changes as we increase or decrease the powder charge. The type of accuracy we get with a micrometer lets any of us get the same measurement value as anyone else. Micrometers are standards-based tools; consumer-class chronographs are not. They yield reliable measurements of our component combinations, but they are not laboratory quality instruments.

I initially wanted a chronograph to confirm that I was not overloading by mistake. Now I want to know if standard deviation and extreme spread can point to specific issues like incorrect neck tension or problems with crimp. Has anybody discovered a connection?

 

[climbnjump]

Micrometers are standards-based tools; consumer-class chronographs are not. They yield reliable measurements of our component combinations, but they are not laboratory quality instruments.

Yeah, pretty much...

For a discussion of various chronograph designs and factors affecting chronograph accuracy, you can check out this link.

It is a chapter from the book "Modern Advancements in Long Range Shooting: Volume 1" by Brian Litz.

 

[Reloadron]

Yeah, pretty much...

For a discussion of various chronograph designs and factors affecting chronograph accuracy, you can check out this link.

It is a chapter from the book "Modern Advancements in Long Range Shooting: Volume 1" by Brian Litz.

Really good informational link. Thanks for posting it.

Ron