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5 or 3 shot group when determining ES/SD???

 
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  #15  
Old 03-06-2012, 05:15 AM
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Re: 5 or 3 shot group when determining ES/SD???

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Originally Posted by shortpants View Post
I appreciate all the replies guys lots of good info. It sounds like the answer to my question is no there is no standard # of shots used by everyone to determine an accurate ES/SD. So when Joe or Bob say they have an ES of 10 nobody knows how they came to that conclusion. Joe might shoot 30 shots in 3 shot groups and average out the 10 groups while Bob might shoot 3 and call it good. Makes me wonder how useful it is to hear the results of Joe or Bob's tests without a detailed description of how they came to such results?
Great point... which is why I say "the target is the final arbiter." I'd rather see Joe or Bob's long range target photos, preferably with witnesses.
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  #16  
Old 03-06-2012, 07:56 AM
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Re: 5 or 3 shot group when determining ES/SD???

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Originally Posted by green 788 View Post
another thing we have to consider is that barrels don't stay the same across hundreds of rounds of shooting--especially for barrel burning cartridges.
That's news to me. Having worn out 3 or 4 match grade barrels in magnum cartridges getting no more than 1200 or so rounds producing sub 3/4 MOA accuracy at 1000 yards, they all performed the same from first shot to the end of barrel life. "Death throes" of each barrel lasted only a few dozen shots. First indication of nearing the end of barrel life was sight settings for a given load, range and altitude had to come up about 1 to 1.5 MOA due to throat erosion.

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Originally Posted by rscott5028 View Post
Shoot 30 three shot groups. And, calculate the average for each 3 shot group. Then, take the ES/SD of the 30 averages and you'll begin to have a pretty good idea of future performance.
One's better off shooting one 90-shot group then do the math for ES/SD as well as mean shot radius. 'Course, if one doesn't belive tried and true statistics, then do something else.

Arsenals testing small arms ammo for all sorts of data shoot several dozen (a few hundred in some instances) shots per test group to get the best, most reliable data possible. Ever seen a 300-shot test group of 30 caliber ammo done at 600 yards?
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  #17  
Old 03-06-2012, 09:21 AM
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Re: 5 or 3 shot group when determining ES/SD???

Bart,
Are you saying for every load one wants to test they should shoot 90 shot groups or is this a hypothetical? You would need your barrel maker's # on speed dial!
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  #18  
Old 03-06-2012, 11:28 AM
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Re: 5 or 3 shot group when determining ES/SD???

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Originally Posted by Bart B View Post
That's news to me. Having worn out 3 or 4 match grade barrels in magnum cartridges getting no more than 1200 or so rounds producing sub 3/4 MOA accuracy at 1000 yards, they all performed the same from first shot to the end of barrel life. "Death throes" of each barrel lasted only a few dozen shots. First indication of nearing the end of barrel life was sight settings for a given load, range and altitude had to come up about 1 to 1.5 MOA due to throat erosion.

One's better off shooting one 90-shot group then do the math for ES/SD as well as mean shot radius. 'Course, if one doesn't belive tried and true statistics, then do something else.

Arsenals testing small arms ammo for all sorts of data shoot several dozen (a few hundred in some instances) shots per test group to get the best, most reliable data possible. Ever seen a 300-shot test group of 30 caliber ammo done at 600 yards?
3 shot groups, 5 shot groups, 90 shot groups don't matter.

There are ways to structure your testing to isolate different variables.

And, there are ways to statistically analyze whatever data you collect.

Regardless, the more good data you have, the higher confidence you can have in predicting future performance.

As to the OP, I get the feeling that most people eyeball the numbers and targets and just throw out numbers. I pay attention. But, it's just a reference point. I mostly focus on documenting my own performance so that I can tell whether I'm moving forwards or backwards because that's really all that I can control anyways.

-- richard
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  #19  
Old 03-06-2012, 11:52 AM
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Re: 5 or 3 shot group when determining ES/SD???

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Originally Posted by shortpants View Post
Are you saying for every load one wants to test they should shoot 90 shot groups or is this a hypothetical?
No. 90 shots in one group's better than thirty 3-shot ones.

For any one load, 15 to 20 shots is a good cost-effective number. It'll tell you what will happen all the time with about 75% to 80% confidence; statistically speaking, that is.
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  #20  
Old 03-06-2012, 02:21 PM
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Re: 5 or 3 shot group when determining ES/SD???

Bart... what magnum cartridge were you using that was ready for a new barrel at 1200 rounds? Or did I misunderstand your post?
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  #21  
Old 03-06-2012, 08:58 PM
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Re: 5 or 3 shot group when determining ES/SD???

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Originally Posted by green 788 View Post
Bart... what magnum cartridge were you using that was ready for a new barrel at 1200 rounds?
.264 Win. Mag. lasted 640 rounds. Three .30-.338 Win. Mag. barrels lasted about 1200 rounds.

The 26 caliber one was a sub .6 MOA rifle at 600 yards, sub .8 MOA one at 1000. That's what the best match bullets available back in the late 1960's would produce.

30 caliber ones were/are sub .4 MOA at 600 and sub .6 MOA at 1000.

I know of no 26 or 30 caliber rifle producing 25+ shot group accuracy at that level burning 65 + grains of powder doing so for more than 1300 rounds. Of course, there may well be some that'll shoot smaller groups with fewer shots once in a while (but there's other groups that are much larger) and have more barrel life under those conditions, but for long range high power competition, you gotta have good accuracy that lasts for at least 25 shots fired a minute or so apart.
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