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Reloading Techniques For Reloading


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? on ES / SD

 
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  #15  
Old 06-02-2008, 04:15 PM
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Quote:
Originally Posted by piutemike View Post
GG, Thanks for the explanation and I now understand how you can have a high extreme spread and still have a low SD.
You're welcome!
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  #16  
Old 06-03-2008, 06:43 AM
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Actually, for a large number of shots with uniform ammunition, the ES is described by 6 SD's. Said another way, the SD is 17% of the ES. This is an application of Statistical Process Control.
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Last edited by Winchester 69; 06-03-2008 at 07:02 AM.
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  #17  
Old 06-03-2008, 12:39 PM
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Win 69,

How 'bout running a standard deviation on my ten shot string mentioned earlier?
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  #18  
Old 06-03-2008, 01:57 PM
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Originally Posted by goodgrouper View Post
How about running a standard deviation on my ten shot string mentioned earlier?
The 3050 fps round contradicts the stipulation of uniform ammo due to the hypothetical tight neck. If I get a chance later, the remaining nine shots could be an interesting study. What SPS does is to identify units outside of process expectations, those having "special cause" influences, such as your tight neck.

The technique doesn't dictate your results, but it does give you an indication of the capability of your process. When the results don't meet expectations, it gives you a place to start looking. You also need more data than a single 10-shot string; otherwise you're in the world of sampling, which is not a corollary to SPC.

The purpose of my commentary is to establish the relationship between ES and SD under conditions of an in-control process. If the results don't follow, then external influences exist, whether they be ambient temperature, component, measuring error, or procedure.
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Last edited by Winchester 69; 06-03-2008 at 02:11 PM.
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  #19  
Old 06-03-2008, 02:25 PM
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GG you describe a glass half full.
I'll describe a glass half empty.
I think the ammo described producing an ES of 50(because of whatever), sucks. You could generalize the results and accept things in a rosey way..
Or, drop the brass in a can and try again, and again, focusing your efforts until the ES problem is resolved. You might find another offender later, an H20 capacity mismatch, or eventually a die problem..

Regardless of the cause, your ES was 50. That's a cold hard fact

Last edited by Mikecr; 06-03-2008 at 04:01 PM.
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  #20  
Old 06-03-2008, 02:38 PM
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Thanks everyone, i understand now.
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  #21  
Old 06-03-2008, 06:42 PM
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Quote:
Originally Posted by Mikecr View Post
GG you describe a glass half full.
I'll describe a glass half empty.
I think the ammo described producing an ES of 50(because of whatever), sucks. You could generalize the results and accept things in a rosey way..
Or, drop the brass in a can and try again, and again, focusing your efforts until the ES problem is resolved. You might find another offender later, an H20 capacity mismatch, or eventually a die problem..

Regardless of the cause, your ES was 50. That's a cold hard fact
Exactly, my take is you can no more throw out one unexplainable velocity than you can an uncalled flyer in a group. If you don't rectify the problem then that same shot could occur on a long range shot at the (fill in the blank) of a lifetime.
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