OzFclass

IanP wrote:I spray painted the bright aluminium support bar for the sensors black to eliminate the chance of the support causing errors in the bright Oz sunshine.

That sounds the most likely cause so far - I'll get out the "Pot Belly Black"

Alan

I tried my new Millenium chronoghraph C2 out today.
I was very disapointed in the results that I got out of it.
I tried three rifles out and all of the speeds were 55 to 60 fps slower.
These Rifles ran at 2970 FPS when chronographed with a Ohler in the SA State team squad.
My results wth my new toy ran at 2907 average and I checked every thing out i case I might have made a mistake i setting it up.
I think I will take it back to the supplier whom I purchased it from and get it checked out.
Very disapointed
Rich

Rich,

I wouldn't be overly concerned about low readings. What you can do is get a comparison with a chrono whose velocities you believe, and just apply a correction to your own figures. In my opinion the most important thing is that shot to shot velocities are accurate so that you can get a good idea of Std Dev or ES. What I have done to test this is to put another chrono in series with the CED and get simultaneous measurements. I have found the difference with my Chrony F1 to be reasonably consistent, which suggests that both are quite accurate. The difference varies between about 25 and 35fps, with the CED measuring lower.

BTW I'm currently in discussions with CED Hong Kong about the errors I've had in mine. They're asking me to do further testing, but the more I do the more sure I am that one of the sensors is faulty.

Alan

Hi Ric
The chrony is only a tool to compare one shot to the next
below is the CED and Ohler comparison
The first lot the CED was in front the second behind
BTW this is the SARA chrony you probably used
So which one is right who knows!
Its all relative
Cheers
RB



CED OHLER CED OHLER
3100 3115 3071 3109
3133 3142 3049 3095
3145 3140 3077 3120
3121 3136 3051 3080
3120 3126 3034 3081
3092 3123 3072 3097
3108 3129 3115 3125
3111 3116 3096 3123
3112 3118 3078 3125
3125 3138 3089 3132
3116.7 3128.3 3073.2 3108.7

Richard, I understand that you would be disappointed to find a difference between the two chronos. You have obviously accepted that the Ohler chrony used by the state team was correct.

I worked in a metrology lab for a couple of years testing and calibrating instruments. In order to accept an instrument's output as being correct it needs to be tested against a known calibrated standard that has NATA (preferably) ( http://www.nata.com.au/ ) accreditation.

To make a quantum leap of faith (not necessarily fact) and say because it differs from the ohler chronograph it must be wrong, just doesnt make good sense. The only way to draw a conclusion about your CED M2 chrony output would be to test against a known standard under identical conditions.

Ohler dont make their model 35 and 43 chronographs anymore and to the best of my knowledge can no longer be bought. ( http://www.oehler-research.com/model35.html ) From all I have read and looked at so far the CED M2 is the best out there for the money that is currently available.

Spot on Ian
Cheers
RB

Hi All
I returned my faulty chronograph and got a replacemet unit.
I trialed it today with very pleasing results.Very impressed with it.
The unit matched the Ohler that the speeds were compared with.
I did quite a few loads using 2206h powder and 2208.
I think that my loads were a tad low for 556
Rich

Good news Richard!

You got a nasty stutter, stutter, stutter though.

IanP wrote:...You got a nasty stutter, stutter, stutter though...

Some people like to do things in triplicate, but I deleted two of them.

BTW my M2 left for the US about a week ago. The testing I did convinced them there was a problem.

Alan

Good News Allan
I must say that they are good with there service.
Mine arrived here direct from America in three days.....very impresive.
I suppose now when you get it back you will be very happy with it.
I am glad I started this thread....every one ended up happy.
Good shooting
Cheers Rich

As mentioned above, I sent my CED M2 to the US - took 4 weeks from posting to receiving. To my embarrassment, they couldn't find anything wrong with the suspect sensor - I can only think it fixed itself somehow, in transit perhaps, because the problem was clearly following the sensor when I switched either sensors or switches around. Anyway, top marks for their service - they even put a spare sensor in.

Just to make sure, I did some testing today, about 25 shots in tandem with my trusty F1 Chrony. Once I figured out a few finer points, I had excellent agreement between the two. The last 20 shots showed minimal difference between them averaging 6 fps with max difference 9fps and minimum 2 fps. What this says is that BOTH chronos are consistent to within 7fps and if I use them in tandem, the average will probably be better than 4 fps. So for what I use them for, which is measuring velocity variations for a given load, they are plenty good enough.

I mentioned some finer points - I had very poor comparison results (up to about 60fps !) before making some changes to the setup. Unfortunately I didn't do what you're supposed to do and change one thing at a time. However even if I had, I couldn't be sure which chrono was the erratic one. Firstly I allowed them a short period of warming up, and secondly I moved them further from the muzzle. If I had to pick a likely culprit, it is that the CED didn't like being too close - why? - because with those bad results I got, the CED reading was much lower than expected and the F1 result seemed about normal. And also because the CED people had asked me to increase the distance to "20ft" during the initial testing before I sent it. So from now on I will go at least 7m.

Any other experiences on warm-up or distance from muzzle?

Alan

Hi Allan
Good news,I told you that thier after sales service was excellent.
Its the first I have heard about 7 metre distance from the muzzle ,I will take it on board.Warming up the chrono.....another first for me.
I was told that the critical thing is when you are putting the sensors on the rail they have to lock into the exact place...If they are out a smigen they will give you funny readings.Well all is well in Fraserville .... lol.Good shooting
Cheers Rich

Do we have a testing facility that could calibrate/ verify the accuracy of chronys??

agro