Whats everyone doing?
- Thread starter clrems77
- Start date
Depends on how many loads I work up. But I try to use it always when I am developing loads. Once I get a load I like. I do an average from 10 rounds. Cold bore and on warm days to know how the temp is effecting my velocity
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Depends on how many rounds it takes you to knock it off the tripod 
If I am using a standard chrono (my CED M2), I'll shoot everything through it because sometimes the velocity explains something about the shot that the hole in the paper can't tell you.
If I'm using a MagnetoSpeed, since it changes the POI I make extra loads - 3 to 5 - at selected charge levels to get an idea about velocity. Once I've gotten to a good load, at some point while shooting I'll run 10 across the MagnetoSpeed. The bayonet may change the POI but it doesn't seem to affect group size.
If I were competing I'd probably want more data points (eg 10 or more) to ensure the batch made factor and to make calculating an SD reasonable.
If I am using a standard chrono (my CED M2), I'll shoot everything through it because sometimes the velocity explains something about the shot that the hole in the paper can't tell you.
If I'm using a MagnetoSpeed, since it changes the POI I make extra loads - 3 to 5 - at selected charge levels to get an idea about velocity. Once I've gotten to a good load, at some point while shooting I'll run 10 across the MagnetoSpeed. The bayonet may change the POI but it doesn't seem to affect group size.
If I were competing I'd probably want more data points (eg 10 or more) to ensure the batch made factor and to make calculating an SD reasonable.
This is what I do as well. I periodically retest to make sure things are still good.
That is what I do. Granted if I am some place where I can set up I will.
Just guessing here, but I suspect - like me - you can't wait for the Labradar
This is really a statistics question.
In the field of six sigma, there are varying opinions of how large a sample population must be for you to run a good statistical analysis. Usually that number is between 25 and 35 - and that's IF you can truly consider your sample population "random".
Loading a batch of ammo once and checking it's speed would not be considered a truly "random" sampling. Better would be to chrono 2 or 3 rounds from each batch of ammo you load, and after a dozen batches have been chrono'd, calculate the mean (average) and standard deviation (SD) for that entire 25-35 round sample population.
SD has a very significant purpose, and lots of really smart people have devoted their careers to how to properly implement it.
In short, assuming you've got a GOOD measure of standard deviation...
Your mean value +/- 1 standard deviation will give you a spread that will represent ~69% of ANY SAMPLE EVER. That means any random sample you take later has a 69% chance of falling into this spread.
Your mean value +/- 2 standard deviations will give you a spread that will include ~99.4%
Mean value +/- 3 SDs will include 99.9997%
...which is why "six sigma" (+/- 3 SD's) is the gold standard of goodness.
So ideally, you'd fire 30 truly random rounds over the chrono, find your mean and your SD, multiply your SD by 3, then add and subtract 3 SDs from your mean to give you a true hi/low limit of what you could expect 99.9997% of the time.
How much dilution of the ideal can you get away with and be ok? I'm pretty happy buzzing 5 or 6 over the chrono before a match and using whatever average it calculates. Sad fact is our rifle barrels are ever changing. I shoot a 6mm that seems to slow down ~10fps every 100 rounds once it's got 500-600 on it.
In the field of six sigma, there are varying opinions of how large a sample population must be for you to run a good statistical analysis. Usually that number is between 25 and 35 - and that's IF you can truly consider your sample population "random".
Loading a batch of ammo once and checking it's speed would not be considered a truly "random" sampling. Better would be to chrono 2 or 3 rounds from each batch of ammo you load, and after a dozen batches have been chrono'd, calculate the mean (average) and standard deviation (SD) for that entire 25-35 round sample population.
SD has a very significant purpose, and lots of really smart people have devoted their careers to how to properly implement it.
In short, assuming you've got a GOOD measure of standard deviation...
Your mean value +/- 1 standard deviation will give you a spread that will represent ~69% of ANY SAMPLE EVER. That means any random sample you take later has a 69% chance of falling into this spread.
Your mean value +/- 2 standard deviations will give you a spread that will include ~99.4%
Mean value +/- 3 SDs will include 99.9997%
...which is why "six sigma" (+/- 3 SD's) is the gold standard of goodness.
So ideally, you'd fire 30 truly random rounds over the chrono, find your mean and your SD, multiply your SD by 3, then add and subtract 3 SDs from your mean to give you a true hi/low limit of what you could expect 99.9997% of the time.
How much dilution of the ideal can you get away with and be ok? I'm pretty happy buzzing 5 or 6 over the chrono before a match and using whatever average it calculates. Sad fact is our rifle barrels are ever changing. I shoot a 6mm that seems to slow down ~10fps every 100 rounds once it's got 500-600 on it.
I'm not saying you're wrong on how to do statistics, but there's more at play when hitting targets. Our scopes don't have the precision measurements to do much more than what a sample of ten has to offer.
Typically when i'm testing loads, i'll shoot groups of 4, then shoot another rifle allowing a for a barrel cool down. I usually load about 16 rounds per recipie for a complete "test" I then simple average all the velocities and shot groups and log my data into my Excel spreadsheet. I've tested over 80 different recipies of .223 and .308 , and i've got some excellent recipies with different powders and bullet weights. As they say, "versatility is the key to sucess". I've also learned a lot as well from digesting the data with respect to bullet weights affecting velocities, ambient air temps and so on. The only suck factor about using a chrono is the fact they tend to be fussy with light conditions. My Alpha Chrony does not like varied passing sun and clouds, or low sunlight such as early morning or late afternoon. The best conditions from my experiences is brighter overcast and using the diffusers.
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