I understand that the lower the SD number the better. What I don’t know is what is considered a good value.
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What is a good SD ?
- Thread starter oldfatguy
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I like for mine to be under 10.
Some people scoff at my 10 and want it around 4. Obviously the smaller dispersion the better but you have to find your point of diminishing returns.
Find out how large your target is, run a calculator with your average speed and see how much you have to go faster or slower to move you off the target. If you are within that region then you need to figure out if the juice is worth the squeeze for you to continue to try and get it down.
At 500 it will matter less than it does at 1k yards.
Some people scoff at my 10 and want it around 4. Obviously the smaller dispersion the better but you have to find your point of diminishing returns.
Find out how large your target is, run a calculator with your average speed and see how much you have to go faster or slower to move you off the target. If you are within that region then you need to figure out if the juice is worth the squeeze for you to continue to try and get it down.
At 500 it will matter less than it does at 1k yards.
if you take a large sample its very hard to have numbers in the single digits...ive had several 5 shot groups with 0 to 1FPS ESs and 0 SDs but once you start taking larger samples that all changes....if your in the low doubles for ESs your good.
usually single digits are considered the goal. however what platform are you loading? context is everything.
6.5 Guys talk about load development
6.5 Guys talk about load development
Anything single digits your doing a good job. Consistently on the low end of single digits don't change your method.
D
Deleted member 10043
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Bill Gates walks into a homeless shelter, and suddenly, the average person in the shelter is a millionaire. That is why we have SD.
run some FGMM over your magnetospeed and you will find that what is generally considered to be good can have some funky numbers.
I have chosen to look at ES. On my 6.5creed, when my ES is around 20, SD tends to be around 6 to 9... all rounds hit at 1,400yds on a 100% IPSC. Sometimes wind might push one a hair left or right.
D
Deleted member 10043
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Okay, within your ES is your total variance from top to bottom. Within that variance is your mean. Okay, you got your average. You're good to go. ES is low than average will be tight too and so will the variance near the average. The SD part is relevant if you have mixed bag of numbers with a wide variance within the ES. You want to know how fucked up it is from the average. That is where the SD is relevant. Thus, motherfuckers if you have a single digit SD over a large sample you are going to have a nice ES and a solid average to plug into Raspberry Pi. It goes without saying. The thing to do since people only like to load, measure, and shoot at 100 yards is to load 200 rounds quickly then pluck out 50 and shoot for statistics. It's called a random sample frame with a confidence level of shit. It is just not feasible to load a large enough population to randomly draw a viable sample. This shooter has 45. Most people on here brag about 5 or 10 shots, lol. So, really the question is what is a bad SD number? A bad SD is when you look at your ES and there is nothing near your average. It is possible to have an ES of <20 and a high SD. Like @pmclaine pointed out factory match ammo is notorious at this.
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Under 10 for me. Further the better. I use the SD as a guide to how consistent I am in my reloading. A QC thing. Spife in his first post above hit a nail on the head, IMO, only I apply what he said when it comes to ESs. See what affect the upper end and lower end (MVs) in my ES have on my come-ups at longer ranges. Could do the same thing with SD (per spife, if I read him right), but I use ES for that.
Made up a list. Started with the idea of having a 100fps ES. (I wanted a large ES to encompass some of mine and some box ammo I've recorded). I centered my loads' average MV within that range. I used 10fps increments. Then plugged those MVs into my Strelok Pro. And came up with solutions for 300, 500, 800 and 1000 yards. Just to see the changes in come-ups. Attachment scan of the list-
But to answer your question- under 10.
Quick edit: looks like I used Hornady's Standard Ballistic Calculator, not my SP.
Made up a list. Started with the idea of having a 100fps ES. (I wanted a large ES to encompass some of mine and some box ammo I've recorded). I centered my loads' average MV within that range. I used 10fps increments. Then plugged those MVs into my Strelok Pro. And came up with solutions for 300, 500, 800 and 1000 yards. Just to see the changes in come-ups. Attachment scan of the list-
But to answer your question- under 10.
Quick edit: looks like I used Hornady's Standard Ballistic Calculator, not my SP.
Attachments
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