[Thirties]

Where would I go to read about such things as:

standard deviation
coefficient of variation
mean absolute deviation

I bought a PACT chronograph, and while it works just fine, the instruction manual is so badly organized and poorly written I would be embarrased to put my name on it.

So, their shortcomings have opened up a can of worms for me, as I would like to know more . . .

Can anyone help me out?

[owen]

A statistics book would be the best place to start.

Standard Deviation is a measure of distribution, that assumes that said distibution is normal (looks like a bell curve)

Mean absolute deviation (WAG here) is going to be the average of the difference of each shot from the average velocity.

[Edward429451]

The front section (or rear) of loading manuals usually have at least some of that kind of info.

[Penforhire]

While you can certainly find some definitions on the web, if you're seriously interested in the meaning behind statistical terms (beyond the basics like mean, median, mode, average, and population standard deviation) I highly recommend "Statistics for Experimenters" by Box, Hunter, and Hunter. I am assuming you're comfortable with basic mathematics.

Otherwise you can ask here for specific terms. I'm with Owen, that "Mean Absolute Deviation" is an unusual term. His guess is as good as any. If true, it would tell you less than the Standard Deviation.

[Steve Smith]

The mean absolute deviation (often inaccurately called the mean deviation), is defined by

http://mathworld.wolfram.com/mimg1301.gif


where the sample size is N, the samples have values , the mean is , and is an absolute frequency

[owen]

HAH!! I was right

It's the mean of the variation from the mean

[Steve Smith]

Which tells you practically nothing.

[Thirties]

"Which tells you practically nothing."

Indeed, I am learning nothing. Why did I get that blasted chronograph anyway?

Accuracy and consistancy of velocity are not closely related in handgun shooting, from my meager observations.

[Penforhire]

Well... velocity variation is certainly one of the limiting factors of accuracy. But it sounds like you have some other uncontrolled variable. In the absence of cross wind (indoors) velocity variation should show up as vertical stringing (assuming you're holding the sights-to-barrel perfectly vertical).

I know one of my reasons I want to handload is to have direct finely variable control over velocity. So I'll be buying a chrony too. The chony helped me develop air-smithing skills with paintball markers. I'm expecting for a similar firearms benefit.

[Thirties]

I am indeed getting very consisant speed in my loads. There is no doubt about that. The chronograph is what gives me that information -- unobtainable any other way.

But my accuracy seems to have no relation to the lack of velocity deviations (so far).

I need to load more experiments and search for accuracy, now that I have got the velocity tamed.

I had naively expected accuracy to go hand in hand with velocity consistancy. I was wrong. There is more to accuracy than I yet understand.

However, this is a work in progress. I am still enjoying it. But there are unexpected bumps in the road.

[owen]

Steve, that is not important!!! I was right!! Im having one of those days when being right, just once is quite important!

:-P

[Steve Smith]

Thirties, consistent speed, if anything, may give you less horizontal stringing at long distances. It is not the only thing when regarding accuracy. More accurate loads have been developed without the use of a chrono than with. The chrono is more of a safety check than anything and CAN be used with the Audette method or the modified version of it, to obtain an ideal load for varying conditions. Mind telling us about your load?

[Thirties]

"Mind telling us about your load?"

.38special
Hornady HBWC 148gr
Bullseye 2.8gr
OAL: 1.166"
Winchester WSP primers
roll crimp (soft)
used brass
handgun= SW model 15 with 4" barrel

avg chronograph velocity = 716 fps with a mean absolute deviation of 8.1 fps.

Shooting off hand I was much more accurate with some Aguila 158gr metal point.

As I said, I'm still working on my loading _and_ my shooting. This is my 7th batch of .38spl loads. So you can see I have a long way to go.

My lesson so far: small M.A.D. does not automatically yield high accuracy. I'm working on achieving greater accuracy which is my goal.

For starters I'm going to load some 158gr SWC bullets to see if I can approach the Aguila accuracy.

[Steve Smith]

Don't take this as an insult, because its definitely not. Shoot it off bags, and have someone else try it. Its hard to make a pistol not shoot well inside of 25 yards unless its a real dog. Could just be you. We don't know what your group size and distance are, either, and we don't know what you're expecting.

[Thirties]

Steve, I don't take your suggestion as an insult. For more info visit this link:

http://www.loadyourown.com/ubb/Forum2/HTML/000251.html

[Steve Smith]

Normal stuff...measure your throats, slug your barrel, size your lead appropriately, check your forcing cone and crown, maybe try switchng primers.