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1 Bullseye
At 23.8 I started getting a little sticky bolt lift that is why I backed it off to 23.6 and all is fine there. Groups are .500 or better when I am doing my job behind the bolt.
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21 Bullseyes
Sd is useful if you know the theory, a better measure (in my humble opinion) is es (extreme spread). Es will give you insight into vertical at range, and more important tells you in fewer rounds if your able to keep your loads in the sweet spot you worked so hard to determine with load development. If your es is large then your oal is hard to determine.
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105 Bullseyes
I agree with Eric's comment to a point but there are exceptions to every rule or thought…
My point on why SD is still so important to pay attention to…
Take 2 – 50rd ammo boxes (reloads) into consideration.
Shooting 5 shot groups (10 groups per box) @ 300yrds so we can fully see the effects of ES…which box do you think will produce the best groups?Box 1 – Your reloads consist of 48rds @ 2500fps with only 2rds @ 2600fps (SD = 19 / ES = 100)
Box 2 – Your reloads consist of 25rds @ 2500fps and 25rds @ 2600fps “mixed” up in the same box (SD = 50 / ES = 100)Box 1 – On average you should shoot 8 “great” groups and 2 average because the “lot” is consistent.
Box 2 – Good luck picking 5 rds with the same fps!!! The odds aren't in your favour at all for even 1 good group. Box will most likely produce 10 average groups…2 completely different outcomes with the same ES…
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21 Bullseyes
Good evaluation Dogdown! i would however point out that most load development is done with groups fewer than 5 rounds and SD is more relavent with larger sample sizes. From a preliminary load development standpoint I (without evidence ) still consider ES a better first take on load development. If you want to get a better evaluation of load consistancy we might go for 7 -8rounds, according to a Google search on best number of shots for evaluation. Fact is Dogdown has more practical exp than I do.
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105 Bullseyes
Eric You misunderstood…
The example was not based on load development, it was a based on “1 load” with 2 – 50rd boxes, 1 box reloaded with low SD, versus 1 box loaded with high SD…but “ES” being the same.
Data measured from each full 50rd box.ES in this situation above would have told you nothing…SD however would have told you why 1 box grouped better than the other shooting 5 shot groups at the range.
In theory you can't have one without the other..But most “modern” shooters in the long range world today whether it be hunting or bench shooting are concerned more about repeatability / uniformity so they can predict what a load will do…ES used to be the main focus for reloading, now both ES and SD go hand in hand. SD is excellent for helping you select the correct elevation turret for a scope or to make drop charts, there will always be a variable in reloading…I myself have had really good success shooting small groups and hitting long range targets by focusing on SD…my guns / scope combos have done exactly what it should when I dial my turret.
Here's how “Brian Litz” (Ballistician @ AppliedBallistics) weighs in on the topic…copied from another forum:
“Standard Deviation is a very useful number for quantifying velocity uniformity. Using ES, you're only using 2 of the shots in the group to quantify the variability of velocities. However, SD uses all the information available.
ES is a good number to get the 'gist' of a loads potential. It represents something easy to understand, and should not be discarded. However, SD has it's place in shooting as well. It's not as obvious what it is, physically; and it's harder to calculate, but it allows you to make some pretty useful predictions.”
No one is wrong on the ES versus SD topic but a good reloader should focus on both if they want to have repeatable success at the range and improve their entire routine / technique. ES is the easiest thing to calulate if you are new to reloading but its doesn't stop there.
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