Chronograph recomendations
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goodgrouper
Well-Known Member
I never got to test the IR kit but I am sure about the five shot groups for SD. Perhaps there is a way to program this to 3 shots? The one I used may have been pre-set for 5 shot only.
GG,
You're right about the CED M2. For the older model, they sell custom mounting brackets for 4 ft, 6 ft, and 8 ft long. These can not be used with the M2. You would need 2 tripods for the 6 ft and 3 tripods for the 8 ft. It seems like they do not deem it necessary with the CED M2.
I hear a lot of folks having problems with readings, I think we need to slow down and read all the recommendations for setting it up in the different lighting conditions. I don't have any problems with mine and that's the older model, nor my hunting buddy with his; the newer M2 is even better.
You're right about the CED M2. For the older model, they sell custom mounting brackets for 4 ft, 6 ft, and 8 ft long. These can not be used with the M2. You would need 2 tripods for the 6 ft and 3 tripods for the 8 ft. It seems like they do not deem it necessary with the CED M2.
I hear a lot of folks having problems with readings, I think we need to slow down and read all the recommendations for setting it up in the different lighting conditions. I don't have any problems with mine and that's the older model, nor my hunting buddy with his; the newer M2 is even better.
Eaglet, you are spot on. While at the range one day some guys were having trouble getting good readings with a CED with the infa red sky screens. I looked at thier set up and told them that they had one screen in the light and one in the shadows. One of them siad " I have the infa red screens". I said yea but they need to be in the same light, both in the shade or both in the light.
Finaly they corrected the bad set up and no problems after that.
Finaly they corrected the bad set up and no problems after that.
BHP9
Well-Known Member
I downloaded and read both the Millenium and M2 manuals, and the only thing I found was, in the M2, you can get the average of the 3 highest velocities (page 10).
Nothing found about programing the # of shots per string.
If you want a 3 shot string, shoot your 3 shots, hit review (if it's like the Pact Professional) the average, ES, etc should be displayed. Then hit next string. Samething over again.
That is what gg stated that it would not do for 3 shots but, would do for 5. That is at least how I interpreted his reply.
BHP9
Well-Known Member
I re read the manual and on page 9 it states that you need 5 shot's.
So you will have to change to 5rd groups.
My Pact Professional calculates everything on the fly.
Forester
Well-Known Member
My M2 will not calculate SD on less than a 5 shot sample. It will of course do ES, thats just subtraction.
I never saw it as that relevant because SD on a sample that small is not very valid anyway. I also tend to use ES as my measure of a loads consistency because it is both a tougher standard and more relevant measure anyway.
I never saw it as that relevant because SD on a sample that small is not very valid anyway. I also tend to use ES as my measure of a loads consistency because it is both a tougher standard and more relevant measure anyway.
goodgrouper
Well-Known Member
I have to disagree on several points. The 3 shot group has plenty of validity to it especially when you re-test that load again and it proves itself over. On magnum rifles with skinny barrels, this is pretty well the only method to use as the barrel heats up you can get bad data from a 5 shot group especially in warm weather. I have seen many people toss out "bad loads" with 5 shot groups because the last two shots went faster and in reality, the load could have been fine.
I also disagree that ES is a better measure of the uniformity of the load. The SD and ES are certainly related but the SD is a better "overall" indicator of the deviation from the norm just like it is named. Or in other words, the ES is the window of velocity but the SD is the variation found in that window.
Forester
Well-Known Member
If you re-test the load then you have effectively increased the sample size. For magnum loads or any load that heats the barrel too much I would just suggest waiting to let the barrel cool to the same point to prevent heat from changing the results.
I would not consider a sample of 3 to represent with any significant level of confidence the performance of a large number of rounds. You can get pretty deep into the statistics involved but to predict the performance of a large number of rounds, say 100, you need to test more than 3.
I am not saying SD is not a valid way to measure a loads consistency, simply that low ES is a tougher standard to meet, like using a 5 shot group instead of 3. My reason for using ES is mostly this; SD is a statistical way to predict deviation from the norm given a certain data set, ES is the actual observed velocity spread. I place more value on my actual measured numbers than on a prediction.
I don't mean to say that ES is the whole story, I suppose you could have a load with very consistent velocities but once in awhile throws one shot 100fps high or low...both the SD and ES might be fine, but I would not trust it.
The bottom line I think is you have to test and test and test to be sure that you won't get some unpleasant surprise on the shot that counts.
goodgrouper
Well-Known Member
Waiting for a 5 shot string when it won't tell you much more than a 3 shot string is very hard to do sometimes. I run a fully operational ballistics lab and I simply don't have all day to wait for barrels to cool down from five shot strings. So I do three and I have never had any gun not hit a 22" gong at 1000 yards using load development methods with 3 shots strings. If the load won't get a low sd on the first go around, it gets left out. BUt if it does, and produces good accuracy and is in a node, it gets re-tested on another day. In this way, I quickly narrow down what load the gun wants without shooting another 60% more ammo down the barrel.
ANd in the world of statistics, standard deviation is the function used mainly and for good reason. It's predictions are much more valuable especially on large quantities of data with similar factors. You could have one shot out of 50 go up in speed 100 fps and you're ES would be horrible. But the SD would show that there was something up with that one round like an extra thick neck, carbon build up, bad charge and so on but the load is still good.
Like I said earlier, ES and SD are related and for all purposes pertaining to our needs, either work fine if you know what to look for.
