Realistic SD and ES Numbers?

[Hunt]

What are you guys realistically settling for in terms of numbers when it comes to ES and SD. I think I have found a decent load that is giving me around 20 ES and 8 SD. Will this work for 1K with minimal vertical?

Lastly, How many shots are in your string before you truly feel comfortable with the load? This load now is keeping me arounf .5-.75 MOA @ 300 yds.

 

[Lindy]

Re: Realistic SD and ES Numbers?

You might find this article on the use of chronograph statistics interesting:

http://www.shootersjournal.com./Features/Haps/EnglemanChronographStatistics.pdf

 

[Winchester 69]

Re: Realistic SD and ES Numbers?

In a perfect world, ES = 3 SD's. You're ahead of the curve. Actually, SD is a calculation that only has meaning in the world of random variation. What does that tell you? Nothing. Zediker, making an empirical evaluation, is of the opinion that any SD below 12 is all you can ask for. Empirical. Based on experience and judgment.

ES is a practical term. Zediker doesn't say anything about it. It gives you an idea of what to expect from you and your equipment. When ES exceeds 3 SD's, some of your product is not being randomly generated. That's when it all has meaning, but only to the extent that you're able to identify the cause of the errant shots, those outside of 3 SD's.

From the information you've acquired, you don't have anything to do, except to practice and build better guns that shoot lower ES's.

 

[Hunt]

Re: Realistic SD and ES Numbers?

With the above said, it sounds like getting anything lower in terms of SD is hard to acquire without a lot of work? In prepping brass, I don't do a whole lot short of cleaning, trimming and chamfering. I'm using Lapua brass to keep weight more consistent.

With that said, what are others able to accomplish in terms of ES/SD for say a 10 shot string?

 

[Greg Langelius *]

Re: Realistic SD and ES Numbers?

Chronos reported velocities are considered by their manufacturers to be accurate to +/-1%. For a reported velocity of 3000fps, this means that this reading will be somewhere between 2970fps and 3030fps true velocity. Simply put, such values are not reliable for purposes beyond the coarse calculation of trajectory drops. Computing ES and SD values of, say, 30fps are simply pure fiction. This is one of the reasons why it is so difficult to correlate such computed values to actual ontarget performance.

I haven't used a chrono in well over a year now, and my load development and shooting processes haven't altered a bit, except to improve a little.

The target tells you what you need to know.

Greg

 

[Bronco]

Re: Realistic SD and ES Numbers?

Guess I've had a little better luck with my chrono than I should have. The best it has ever read was a .8 SD, 11 FPS ES. Shots at 500, 600, and 800 were all 1/2 moa. Pretty good correlation I'd say.

I like to keep ES less than 40 fps, it doesn't always happen.

 

[Lindy]

Re: Realistic SD and ES Numbers?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Chronos reported velocities are considered by their manufacturers to be accurate to +/-1%.</div></div>

The relevant question with a chronograph for measuring SD is not whether the numbers are <span style="font-style: italic">accurate</span>, but whether they are <span style="font-style: italic">consistent</span>, i.e., what the possible error range is for a shot of a single velocity. For measuring SD, consistency matters much more than accuracy.

ES is a figure of questionable merit, as pointed out in the link I posted above.

For calculating trajectories, accuracy matters more, but that's always going to be a ballpark figure, given variations in muzzle velocity.

 

[raptor99]

Re: Realistic SD and ES Numbers?

Correct Lindy. Even though the velocity may very or in some cases be high or low the SD and ES should still be an accurate measure of what your load is doing.

 

[CoCaDoRi]

Re: Realistic SD and ES Numbers?

regardless of error in the chrony's always shoot for the lowest ES and SD numbers.

BR shooters set standards and have invaluable data to be shared. Talk to any and they want ES to be 10 or less.

 

[ChadTRG42]

Re: Realistic SD and ES Numbers?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: inode</div><div class="ubbcode-body">What are you guys realistically settling for in terms of numbers when it comes to ES and SD. </div></div>
Most hunting rifles with good hand loads you can get to within 15-40 fps ES. I think this is acceptable for a hunting rifle used within 300 yards.
My comp guns I want as low as possible. For my custom 260, I found a load with H4350 that shoots 4.5 fps ES, and 1.5 fps SD. I have never seen a load shoot these low numbers. The load is very accurate. I did find a more accurate load with R17, but the SD and ES numbers were not near as good. So, I went with the H4350 load. In competition on a target at 800 yards, there was less than 2" vertical spread. I was very pleased with this load.