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Old June 4, 1999, 10:27 PM   #1
Abe Normal
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I picked up a chronograph just long ago enough to run my first good series of tests.
What I'm finding is that with the pistol calibers I can get the s.d. down in the 6.0 to 10.0 range with little or no problem. But as the caliber go's up so does the s.d. My .223 is around 9.0 to 15.0, my .308 is up to the very high teens to mid twenties and the 30-06 on the very best days is in the mid forties to high fifties.
Is this normal?
I assume that the instructions that came with the chrono were correct in that the s.d. is no more that a averaged number that gives a idea of over all shot to shot consistency.
I find it tough to believe that I can get good results loading .223 and do fair at .308 only to have 30-06 be so far out in left field.
OBTW I'm shooting .223 from an AR, .308 from a Rem. 700 and 30-06 from a DCM Garand.

Many thanks to all that respond for their thoughts on this matter.
Abe
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Old June 5, 1999, 08:17 PM   #2
Bob Thompson
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Good question Abe. I have been reloading for quite a number of years for many diverse calibers and have generally found that for almost any of them and at any power levels that my best accuracy has been acheived with the lowest standard deviation. Sometimes this has been as high as 20 fps difference. Most standarsd calibers will begin high s.d. with hot loads approaching maximum but many magnum loads show small s.d. with the hottest loads. I am currently working with the 30-378 in a nice Savage rifle and my smallest s.d has been with near max. loads. There are many variables that influence s.d but I have found one of the most important is to use the powder which will most completely fill the case and give the results desired. When I load I will sometimes shirk on f.p.s. to obtain the best standard deviation. Hope I have added some usefull info.
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Old June 6, 1999, 09:31 AM   #3
WESHOOT2
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Charles Petty used a stationary barrel-holding fixture and tested the 45ACP. The highest S.D. was the most accurate load. I have seen this same phenomenom when testing 38 and 357. Go figure. Like the Speer manual says, "but not always".
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Old June 6, 1999, 10:33 AM   #4
Abe Normal
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Soooo, if I understand correctly the S.D. is no more than another indicator with the final analyses / real deal being the holes in the paper. Meaning that it would be possible to have a low S.D. and still be punching holes in your neighbors targets (although not likely).
Abe


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Old June 8, 1999, 10:39 PM   #5
WESHOOT2
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True. I, too, try to get low numbers.
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Old June 17, 1999, 03:04 AM   #6
Paul B.
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About 2 gun shows ago I picked up a bunch of HANDLOADER magazines. Anyway mag # 125 July-August 1987 has a serious article on standard deviation. It seems that all these gun magazine "egg-spurts" have got it all wrong. The point he brings out is,"Standard deviation measure VARIABILITY (emphasis is the authors) of the average. That is exactly what it is supposed to do; but for shooters, the result can be misleading if it is used to compare velocities (or any other kinds of values) of different magnitudes."
This article gets a bit complicated, but if you can chase down a copy,(try Wolfe Publishing) it makes for some enightening reading.
Paul B.
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Old June 17, 1999, 06:47 AM   #7
WESHOOT2
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Holes on paper = accuracy, not numbers.

Terminal performance (expanded to more than original caliber and braking bones on the way out) = velocity.

Know what I mean? The proof is in the shooting.
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