Velocity extreme spread and group size

[tacotime]

Checking some loads for 45-70 and found that some loads with low extreme spreads, did not produce better groups that other loads with much larger extreme spreads. 
 
One 5744 load ES was 16 (and with unburned powder left), but grouped poor (maybe 3 inches at 100). 
 
Another 3031 load had ES of 125, but grouped much better (maybe 1.25in). 
 
I was thinking the lowest ES would give a better group.  No?

[MePlat]

I can tell you this from chroning and benching at the same time you will be fooled some times.  A shot that will be an abnomoly on either end may very well be in the group and a shot that is very close to the average may be out.  Or sometimes the abnormal shot may only be out just a tiny bit.
I still like velocity to be farly close though just to cover my doubts though.
It is a learning experience.  You never stop learning unless you stop shooting.
Near perfect bench technique is as important or more important to group shooting than a lot of the other things we ponder over.
If you don't believe it shoot a rifle that a good bencher has that will put them "right in there" and watch someone with bad bench habits shoot it. 

[Larry Gibson]

Lots of things effect accuracy, the ES being one of them.
BTW; unless your test strings are 7 rounds minimum or preferably the industry standard of 10 shots the statistical validity is questionable (you don't say how many shots the ES was based on).  Shooting 3 or 5 shot test strings can give a less than valid ES and SD along with group size.  Using those figures can lead you down a mistaken path.  Best to use a minimum of a 10 shot test string or three 5 shot test strings.
 
Larry Gibson
 

[tacotime]

Good advice.  I was using 4 or 5 shots for the sample.  I'll use more once I get the group narrowed, to be sure about the stats.

[necchi]

Lots of things effect accuracy, the ES being one of them.

That's it in a nut shell. If neck tention was different then you'll get flyers. If a few had some bad runout then you'll get some fliers,,,etc.

[Grumulkin]

First of all, there is no such thing as a "flier."  It's a term invented by gun writers to excuse poor accuracy in guns they test and get paid for testing.  A gun either groups well or it doesn't.


If you calculate how much bullet drop a difference in velocity will make at 100 yards, you will find that even with moderate variations in velocity, the difference in bullet drop is very little.  That means for 100 yard shooting, other factors are quite a bit more important in obtaining good accuracy than extreme spread.  When ranges are increased, extreme spread becomes more and more important.

[tacotime]

Thanks

[Lloyd Smale]

heres my take on it. Velocitys that vary less then 150 fps rarely have much effect on a target at a 100 yards. When you get up around 300 youll see some group opening. Ive seen loads with handguns that varied as much as 300 still shoot just fine at 25 yards. No doubt the best load is one that is accurate and has a small swing in velocitys. Anymore i dont even chrono loads looking at spreads. I personaly think its a waste of time and loading components. If a gun shoots a load good at the range i intended it to i use it. I mostly chrono my final loads just to see where im at.