Guys,

I had to rework my loads...ugh...thankfully I'm done and need a little advice. Below are my velocities for my load. So first which do you use to determine the velocity you use? ES or SD?



Also I use a Chrono and am wondering how accurate it is? How much will sunlight vs shade effect the results? Or will it? I load these very consistently as far as my processes are concerned.

Thanks,

Mel

They are two different measures

Es show your total extreme ranges
Sd shows your centralized data.

As one goes down the other should as well. Sd will look at the entire group. Es will only look at your best and worse

What type of Chrony. Different ones have different accuracies

So I threw your data into a stats program


Some observations (assuming the shots were in order). Your variation was less on the last half. What's odd is the first 3 shots were all less than average velocity. If I omit your first three data points your sd drops to 8.5

I like looking at ES. I want to know what the extremes are. SD is good, but it doesn't tell the whole story.

Looking at your data you posted, Cleric mentioned what I saw. Your overall ES is 44. But shots 4-10 were only 22 fps ES, which is great. But the more you shoot, the higher your ES will go. I put 39 rounds down my 6.5x47 and got 29 ES when I was zeroing at 100, and shot it all the way out to 800 yards, while getting dope. That's still really good for 39 rounds. There were a few that caused the ES to raise. Most were within 5-10 fps of average.

If you have a large sample size (lots of shots), and most are close to the average with a few off, your ES may be high, but have a low SD. If you have a large sample size, with the same ES, but the shots are all over the place, your SD will increase, because the shots have a larger spread.

They are definitely relative to each other and while developing loads I do pay attention to both. I like single digits in both. One of the guns I have that shoots so well has an ES of 3 and an SD of 2 (five shots as I rarely chrono more than that at a time)...it shoots lights out, if I miss it isn't the gun.

I'll pick a combo that shoots low ES/SD's and play with seating depth and primers to tune them in over a combo that shoots awesome but has high ES/SD's. Sometimes you can hit on something and sometimes you can't...just nature of the different barrels liking different things.

Thanks guys! I appreciate it greatly.

The Chrono I'm using is a Chrony. How accurate are they and how much does sunlight vs cloudiness affect it.

They seem to do better on cloudy days from my experience. The ones I have are very close, judging from a couple tests with other chronographs and from plugging the measured velocity into a ballistic program then shooting with the dope it generated.