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Chronograph question.

#8
08-25-2003, 05:03 PM
 Junior Member Join Date: Aug 2003 Location: Franklin, Pa. Posts: 24
Re: Chronograph question.

Well I really got in over my head with that question, Lots more Info then I expected. I do understand it a little better, seems to me bottom line is lower the numbers the better. The rifle I was shooting is a 243, rebarreled with a Shilen tube #5 contour. I use it mainly for deer hunting.
On the other hand I have a 6.5x284 I use for most of my long range ground hog hunting. This is the one I try to do my very best with. I prep brass pretty much the same way with all my guns.

Deburr inside flash hole.
Clean primer pocket with a tool that sets all primers at the same depth. [name??]
Turn outside neck.
Measure all charges with digital scale.
Resize with neck bushings, to get.0001 press

I'm not sure what else there is to do. I haven't checked the 6.5 lately so not sure what the ES-SD is. Thinking 20-25 for ES.

I have to say though, if I had to point my finger at one thing that accounted for most of my misses it wouldn't be the equipment. It would be misjudgeing yardage. Lazer rangefinders leave alot to be desired sometimes.
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PennMonty
#9
08-25-2003, 06:15 PM
 Junior Member Join Date: Aug 2003 Location: Texas Posts: 8
Re: Chronograph question.

Dear Brent:
Here is how you calculate standard deviation.

1) Calculate the mean (average the velocity of the shots...add up all the velocity scores and divide by the number of shots).

2) Determine the amount that each shot deviates from the average. (ex. average velocity 3000, shot #1 is 2990, deviation from mean is -10)

3) Square each deviation score. From the above example -10 x -10 = 100.

4) Add all the squared deviation scores together.

5) Take the square root of that sum of squares (what you did in step #4).

That is the standard deviation (from the mean or average).

Hope this helps but if you want a two-way ANOVA, we are not doing it on-line.

T Sharps
#10
08-25-2003, 11:12 PM
 Writers Guild Join Date: Jul 2001 Posts: 1,459
Re: Chronograph question.

Brent, excellent observation, however, we have seen "round" groups with different vel readings. What I mean is that a "slow" vel shoots higher then a "fast" one, or to the left or right. We have forgotten that vel also relates to barrel time and its harmonics, which in turn determines what barrel location the bullet sees as it leaves the muzzle.

There are so many variables in shooting that vel alone cannot determine accuracy. However, if I had two equally shooting loads, I would choose the one with the lower vel variations..just in case.

Ultimately, the only way to know how a load performs is to shoot is at the range you want to use it at. Like Brent, I have personally had several one hole loads at 100yds that wouldn't stay on a piece of paper at 500yds.

Now, I work up my loads at 180 or 250yds. I find this to be a better representative of LR performance. In general, if a load works well at these ranges, it will work well at further ranges. I find wind and conditions to play a bigger roll at that point.

Jerry
#11
08-25-2003, 11:48 PM
Re: Chronograph question.

Brent,
Since I am hopeless with numbers and stats etc. I ******** the troops and simply say that the SD is an indicator or how uniform the reloads are, relative to each other. Sounds impressive, guys always nod their heads as if I must know what I just said and carry-on. If low SD's meant smaller groups the world would be a simpler place to live in. [img]images/icons/wink.gif[/img]
#12
08-26-2003, 01:05 PM
 Platinum Member Join Date: Jul 2003 Location: Central PA Posts: 1,307
Re: Chronograph question.

Penn Monty - SD in my mind is most easily described as:

the average deviation from the average

[img]images/icons/confused.gif[/img]

dont know if this helps your understanding, but that's the way i think of it.
JB
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#13
08-26-2003, 01:48 PM
 Bronze Member Join Date: Jun 2003 Location: Eastern US Posts: 61
Re: Chronograph question.

I think that T-Sharps must have some background in stats, science or engineering. Not that that's a bad thing, just takes one to know one! Just an observation from one number cruncher to another [img]images/icons/grin.gif[/img]
#14
08-26-2003, 05:23 PM
 Junior Member Join Date: Aug 2003 Location: Texas Posts: 8
Re: Chronograph question.

Mountaineer, is it that obvious? I thought I was being SO clear and easy to understand.

T Sharps

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