SD ES Tolerances

[hunter24605]

How do you set and acceptable SD? Is it a fixed number, or a dependent upon cartridge? I may be way off base, but I've been using a SD of 1% of the average as the upper limit. For instance, a 3000 AVE velocity of a 5-round string would have a 1% SD upper limit of 30. I strive for a goal of .005% of SD. Should I not base it off AVE velocity? is under 1% good for a TOP end SD?, should I ditch the math and go with set numbers, (like an SD of 10)?

 

[RL338]

should I ditch the math and go with set numbers, (like an SD of 10)?

Yes & Yes
Too much math makes my head hurt

 

[KinleyWater]

Got confused at first thinking you were talking about sectional density. Anyway - I suppose I don't give a lot of thought to it, but I would worry more about functional groups than chasing numbers.

 

[JD338]

Although I strive for single digit ES and SD, I have several loads that are from that. And once you start using a new batch of powder or primers, those ES and SD numbers are going to change.
Don't get hung up on these as it's just a snap shot of your load.

JD338

 

[Blkram]

I know that most people recommend single digit SDs as the goal for consistency working towards accuracy...

But it is interesting how many reloading articles I have read over the years where the more accurate loads recorded in various rifles, with various bullets, powders, primers, etc., are not the loads with the lowest SDs in those particular rifles. Quite often they are SDs in the double digits and sometimes in the 20s and 30s, or more...and in many instances these were not from just one group but an average of 3 to 5, 3, 5 and/or 10 shot groups.
So you can take that info with a grain of salt...

At the end of the day, even of the SDs are not in the single digits, but the load is producing consistent accuracy and a velocity that meets your expectations, would you disregard that load in the search just because the SD isn't in the single digits?

Me, I would be happy with the current performer. If I am getting single digit SDs then I am even happier, but it isn't my first priority. But again, I am a hunter first with most of my firearms, not a target competitor.

Only you can decide what is your priority.

 

[TackDriver284]

I strive for low ES and SD, and I am capable of low ES / SD in the single digits but I lean more on what the target tells me at long range. If I see a tight cluster, then I'm happy, but if I see vertical or bad groupings, then I will fix my load and variables.

 

[Idaho53]

As a fellow reloader, I too chase the accuracy and consistancy in my loads. Half the fun is trying to make each load/shot the same (it's all the most frustrating when it goes south) In my experience, the single digit ES and SD really only show up on target at long range (like 500 yards plus) My personal testing shows my best ES and SD come from super consistent neck tension (by annealing and using a high quality neck sizing die-LEE collet). Goes w/o saying that seating depth, powder charge, etc. play a role too.

 

[jimbires]

this is internet hype ,that shouldn't be a concern , for most guys . ES and SD is nothing to worry about for most hunters . most game is killed inside of probably 200 yards . I killed a lot of game before I had a chronograph . I put temp sensitive gun powders in the same category .


shooting long range is a whole different game . I watch ES and SD , and try to get them low. what the target says is my goal .

 

[D21ALASKA]

Listened to a couple interesting podcasts recently that touch on this. Long and short of them are that for most of us reloaders, all of the hard data we get from a certain load is from a sample size that is too small to be considered representative of what's really happening. Speaking SD/ES specifically, any bullet/powder combination at any given charge weight will show statistically the same SD/ES when the sample size is large enough.
I've linked the two podcasts below. If you've got a couple hours I highly recommend giving a listen. Interesting enough to make me decide to work my next load up completely different than in the past as an experiment.

Edit: Sorry for the Hornady podcast plug on the Nosler site. Good stuff though.

Edit 2: The links above are for the audio version on Spotify. They're on YouTube as well. Actually helpful to watch them there as they have data charts that they're going over while speaking. I listened first and then watched them at a later date.

 

[hunter24605]

Thanks fellas. I’m primarily a hunter and rarely exceed 300 yard shots on game, so ES and SD are somewhat inconsequential. I like to use the numbers to see what’s going on with certain changes, and when evaluating different powders early on in development. But mostly it’s just fun trying to shrink those numbers down.

 

[RL338]

My personal testing shows my best ES and SD come from super consistent neck tension

Bingo