Acceptable ES and SD

BrentM · Oct 15, 2019

Look up litz WEZ study. Good info. I personally have no issue getting SD 10 or less. ES is usually around 15 or less. Some people tune a specific range such as a ladder, it does work, I used to do it too. For the last few years I use the Satterlee method and find a node with low SD/ES, work inside that node to fine tune, and it works for both accuracy and low sd, which works for a wide range of yardages. It also seems to work very well for extremes in temperature and elevation changes.

Barrelnut · Oct 15, 2019

vitaminado said:
What loading techniques do you use to download sd and es?
I am thinking of buying a concentricity tool and turning my necks, as well as classifying brass by weight.
Do you think it will make any difference to turn the necks for a factory rifle?
In this case it is a bergara hmr 6.5 creedmoor.
i use lapua brass

Lapua brass is pretty high quality. IMO it does not need weight sorting or neck turning.
Lapua braas I have used usually is within 1 Grain in weight and neck size variance around the case neck is a little less than .001. Those are pretty good specs.

basinman · Oct 16, 2019

+ 1 on the single digits for the SD.

rockytop65 · Oct 16, 2019

Barrelnut said:
A SD of 10 would mean that 95% or the rounds would be +20 or -20 FPS of the average. And that 65% of them would be between +10 and -10 FPS.
My 300 RUM with a 210 VLD will have an impact change of +/- .5 MOA at 1000 yards with a +/- 20 FPS change in velocity. That .5 MOA at 1K is a hair over 5 inches. With a 10 inch kill zone .5 MOA is all I could afford.

Kinda supports what others above have said. A SD of 10 or an extreme spread of 20 FPS would be about the limit for 800~1K shot.

Would u like to share ur load data for that round. I would like to try it in mine being I'm using the same bullet.

Barrelnut · Oct 16, 2019

rockytop65 said:
Would u like to share ur load data for that round. I would like to try it in mine being I'm using the same bullet.

Okay

Remington Brass
F215M primer
Berger 210 VLD
COAL = 3.860 (.020 off lands in my well worn barrel)
I run this as a single shot rifle as the COAL is quite long.
87 Gr. H1000
Runs at 2930 FPS. Out of 28" barrel

I used to run it at 89 Gr. for 3120 FPS
Now I just run it easy on a good node around 2950
It has been very accurate though. This load took an antelope at 865 yards this year.

Good Luck with your RUM. Awesome round.

Schnyd112 · Oct 16, 2019

Jumpalot said:
I haven't shot over a chrono in about 5 yrs. A pretty well known gunsmith on here once told me that I could chase numbers or go out and shoot to see what my rifle will really do. He suggested to load up until I saw high pressure (a pretty good swipe mark on the bottom of the case), then reduce the load by two grains and I should be pretty close. I thought he was nuts, but because of his reputation I tried it. Well lo and behold it worked. At least well enough to hold sub MOA out to 1000. I've done it on three of my rifles and my buddy's two rifles. No idea what my ES and SD are. I figure out my velocity through my drop charts. After I've found my pressure load, I go test at 500, 800, and 1000 yds and look for vertical dispersion. If I find any, I might tweak my load a half grain up or down or adjust seating depth a little. But, I've only had to do that on my 6.5x284 and that was a .5 grain increase to get me where I needed. Maybe not the answer you're looking for, but I used to waste a lot of time shooting over a chrono looking for a load.

I wish I had the gumption to do this. Your reasoning is sound, let the rifle tell you what it can do. I definitely chase numbers and can lose confidence in a good load because of one bad chrono session.

The chrono does help explain seemingly random fliers at distance. It doesn't give a solution, just a little piece of mind on why it may have happened.

BrentM · Oct 16, 2019

Schnyd112 said:
I wish I had the gumption to do this. Your reasoning is sound, let the rifle tell you what it can do. I definitely chase numbers and can lose confidence in a good load because of one bad chrono session.

The chrono does help explain seemingly random fliers at distance. It doesn't give a solution, just a little piece of mind on why it may have happened.

Just a guess but it sounds like you are between nodes or on the edge of a node. Perhaps

Schnyd112 · Oct 16, 2019

BrentM said:
Just a guess but it sounds like you are between nodes or on the edge of a node. Perhaps

I would hazard to guess that there is way more variation than you would like to admit. Nothing huge, but a load than chronos 2880-2900 over ten rounds may shoot 2900-2920 the next week. That's 40 FPS extreme spread over two weeks, unacceptable, but it happens. It's why I don't like shooting over a Chrono. Weird things happen and can shake your confidence in a load that shoots great.

Angle, time of day, cloud cover, position, it all changes the way velocities are sensed by the chronograph, or does it? Does that mean the load is inconsistent? Or just that there is a weakness in measuring? I can chase numbers all day and all I get is frustrated. But the ability to measure means I do it consistently and have to analyze what I find.

I wish I could just shoot and convince myself I pulled a shot that missed. But there is real data that shows there are strange things that happen and I struggle to find an explanation as to why this round was faster/slower than the rest and caused a miss.

Jumpalot · Oct 16, 2019

Schnyd112 said:
I wish I had the gumption to do this. Your reasoning is sound, let the rifle tell you what it can do. I definitely chase numbers and can lose confidence in a good load because of one bad chrono session.

The chrono does help explain seemingly random fliers at distance. It doesn't give a solution, just a little piece of mind on why it may have happened.

If I get a flyer, I mark the brass with a Sharpie. If I get a flyer with that piece of brass again, I cull it.

BrentM · Oct 16, 2019

Schnyd112 said:
I would hazard to guess that there is way more variation than you would like to admit. Nothing huge, but a load than chronos 2880-2900 over ten rounds may shoot 2900-2920 the next week. That's 40 FPS extreme spread over two weeks, unacceptable, but it happens. It's why I don't like shooting over a Chrono. Weird things happen and can shake your confidence in a load that shoots great.

Angle, time of day, cloud cover, position, it all changes the way velocities are sensed by the chronograph, or does it? Does that mean the load is inconsistent? Or just that there is a weakness in measuring? I can chase numbers all day and all I get is frustrated. But the ability to measure means I do it consistently and have to analyze what I find.

I wish I could just shoot and convince myself I pulled a shot that missed. But there is real data that shows there are strange things that happen and I struggle to find an explanation as to why this round was faster/slower than the rest and caused a miss.

I don't mess with chrono's. Labradar and magnetospeed. I get your point but still wonder about the node. I've had loads show less than 25 FPS over 100 rounds with .5 grain node. I've had loads do that same with 1 Grain.

Schnyd112 · Oct 16, 2019

Jumpalot said:
If I get a flyer, I mark the brass with a Sharpie. If I get a flyer with that piece of brass again, I cull it.

But now that you marked that piece, are you subconsciously expecting it to be inconsistent? It's easy to blame a piece of brass. It's easy to blame yourself. But the chronograph shows that out of 50 rounds, 2 or 3 were outside of the rest. Standard deviation says this is a normal curve. High volume shooting means you run into that 3-5 in 100 round more often.

So do you just accept that 5% of your shots are more than 2 standard deviations from the mean? Or do you try and circumvent statistics and blame it on brass or skills, be it pulling the trigger or reloading.

Schnyd112 · Oct 16, 2019

BrentM said:
I don't mess with chrono's. Labradar and magnetospeed. I get your point but still wonder about the node. I've had loads show less than 25 FPS over 100 rounds with .5 grain node. I've had loads do that same with 1 Grain.

I shoot over a magnetospeed and have exclusively for 1500 rounds out of this barrel. There is still a lot of difference in the way it is set up. So is the weakness in my setup or is it my load? There is not an answer. It will never be exactly the same. As a person trained to analyze and question data, it just makes it that much harder.

That's my point. I wish I could trust a small sample size and shoot more without it. But that just isn't the case.

BrentM · Oct 17, 2019

Schnyd112 said:
I shoot over a magnetospeed and have exclusively for 1500 rounds out of this barrel. There is still a lot of difference in the way it is set up. So is the weakness in my setup or is it my load? There is not an answer. It will never be exactly the same. As a person trained to analyze and question data, it just makes it that much harder.

That's my point. I wish I could trust a small sample size and shoot more without it. But that just isn't the case.

Yeah, that's a rough one. I don't have that issue. I trust my data and run with it. I am not paid to shoot so having rounds not print .25MOA all day every day isn't going to happen and it doesn't happen for anyone consistently over the life of a barrel. I have zero issue having faith in my rifles, once dialed in, will shoot moa or better. I find the node that is relatively wide and works for that rifle and use it. It seems getting low sd and es is not that hard with quality reloading equipment and consistent process. The only inconsistency I find in field shooting is horizontal scattering, which is almost always wind issues. I cannot recall the last time I had an unexplained vertical flyer.

rockytop65 · Oct 17, 2019

Barrelnut said:
Okay

Remington Brass
F215M primer
Berger 210 VLD
COAL = 3.860 (.020 off lands in my well worn barrel)
I run this as a single shot rifle as the COAL is quite long.
87 Gr. H1000
Runs at 2930 FPS. Out of 28" barrel

I used to run it at 89 Gr. for 3120 FPS
Now I just run it easy on a good node around 2950
It has been very accurate though. This load took an antelope at 865 yards this year.

Good Luck with your RUM. Awesome round.

Thanks I'll give it a try

Acceptable ES and SD

BrentM

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Barrelnut

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basinman

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rockytop65

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Barrelnut

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Schnyd112

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BrentM

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Schnyd112

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Jumpalot

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BrentM

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Schnyd112

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Schnyd112

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BrentM

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rockytop65

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