What “Causes” a Low SD/ES?

[General RE LEE]

Question: what causes a low SD/ES?

I was going through notes and .3 grains made a difference of a SD3 ES7 to a SD12 ES20. How can a slight different in powder charge level create that change?

 

[FEENIX]

Question: what causes a low SD/ES?

Consistency in the overall reloading process.

 

[dflyfish]

Because that's what your barrel liked

 

[backwoodsshooter]

Question: what causes a low SD/ES?

I was going through notes and .3 grains made a difference of a SD3 ES7 to a SD12 ES20. How can a slight different in powder charge level create that change?

 

[backwoodsshooter]

but seriously though, i have no simple answer as someone explained it to me some years ago

 

[General RE LEE]

Consistency in the overall reloading process.

Ive got a system down where I anneal, full length resize, bump shoulder back and trim each case and then I weigh every load. I load in batches of 15-20 and shoot recreationally at the range out to 750 yards. I learned years ago from a competitive black powder shooter that the reloading process of a black powder gun should be exactly the same everytime.

 

[FEENIX]

Ive got a system down where I anneal, full length resize, bump shoulder back and trim each case and then I weigh every load. I load in batches of 15-20 and shoot recreationally at the range out to 750 yards. I learned years ago from a competitive black powder shooter that the reloading process of a black powder gun should be exactly the same everytime.

So "if" you got the "consistency in the overall reloading process" system down, why are you asking the factors affecting SD and ES? You seem to be contradicting yourself.

Question: what causes a low SD/ES?

I was going through notes and .3 grains made a difference of a SD3 ES7 to a SD12 ES20. How can a slight different in powder charge level create that change?

An inconsistency resulted from SD=3 and ES=7 to SD=12 and ES=20, i.e., inconsistencies in powder charges between load configuration.

 

[MagnumManiac]

It all boils down to start pressure. A uniform start pressure equals a curve under MAP that is consistent. A start pressure that fluctuates causes variation in MAP…this is where ES/SD numbers vary causing poor numbers.
There are numerous ways this can be influenced or changed; crimping, seating depth, neck tension and even primer type.
Poor ignition is to be avoided at all costs.

Cheers.

 

[Tiny Tim]

^^^^^^This. Well said Magnum!

 

[nksmfamjp]

When you say you have it "down", I think:
What is the accuracy of your tools/process?
What is your process design?
How did you determine primer type, bullet, powder, neck tension, case fit, case brand, etc?
What are the measured results: predictive like runout or charge variation? Also, final results like group size, sd, mean radius?
Also when you post an sd/es…..how many rounds in the chrono group? By definition, when the sample accurately predicts the population, ES>= 6xSd for a normal distribution.

 

[FEENIX]

When you say you have it "down", I think:
What is the accuracy of your tools/process?
What is your process design?
How did you determine primer type, bullet, powder, neck tension, case fit, case brand, etc?
What are the measured results: predictive like runout or charge variation? Also, final results like group size, sd, mean radius?
Also when you post an sd/es…..how many rounds in the chrono group? By definition, when the sample accurately predicts the population, ES>= 6xSd for a normal distribution.

LL! Now you've done it...

 

[RYEWSKY25284]

When you say you have it "down", I think:
What is the accuracy of your tools/process?
What is your process design?
How did you determine primer type, bullet, powder, neck tension, case fit, case brand, etc?
What are the measured results: predictive like runout or charge variation? Also, final results like group size, sd, mean radius?
Also when you post an sd/es…..how many rounds in the chrono group? By definition, when the sample accurately predicts the population, ES>= 6xSd for a normal distribution.

Genius.

 

[SFMongo]

QA (Quality Assurance) QC (Quality Control). QA same weight, size, and uniformity of your brass and bullets. Quality Control: Accurate and uniformity in loading plus shooting i.e. barrel temperature. Even if you did all this you have no control over your powder quality. Guess what at the end of the day there are two things that will minimize SD just like about everything else in this world. Time and Money. LOL

 

[P7M13]

If this is the order of your process:

I anneal, full length resize, bump shoulder back and trim each case and then

...then I'd say, PFL.
If it's repeatable, just go with it -- you found the secret sauce recipe for your rifle.