ES/SD How important is it?

[ftrrookie]

Reading on this and other forums it seems that most of you competition shooters, when working up a load, feel that having a low ES and SD is important to the accuracy of the load. An example, I posted a load development target in Erik Cortinas great "Long Range Load Development at 100 yds" thread and asked him which group he thought I should pursue. He replied that I had nothing to work with because the ES/SD was too high. But then I've read other ppls posts stating that the most accurate load they've ever shot had high ES/SD.

And this happened to me today. I was doing load development on my Savage FTR 223 and as you can see on the target the smallest group has the highest ES/SD



I shot all the groups then attached my Magnetospeed V2 and started checking velocity. I thought that the 25.6 gr was going to be too hot so I only loaded 3 rnds so no velocity. When I did the next 2 I was surprised at the results so I took the chrono off and reshot them. Got the same results. 25.2 = bughole, 25.4 scattered. The only difference being that instead of a wide triangular group I got a vertical string.

So, can someone explain this to me? Why am I getting better accuracy with higher ES/SD?

 

[stool]

it is very important....
your bug hole group will likely fall apart the further out you go.
and three shot data is very small.......
need more shots across the chonograph...
better yet you need to chrono the shots on the target...which is not practical with your chrono since it affects bbl vibration/weight.

nice toy not much good for checking actual on target shots...

 

[BoydAllen]

At short range, ES (forget SD) is not very important, because the differences in trajectory that it causes is so small. As you back away from the target, it becomes progressively more important. Tune and variation in velocity are related but not the same thing. The trick is getting them both with the same load. One without the other is not of much use at long range. Perhaps you could hold your powder charge constant and play with seating depth.

 

[ShootDots]

I shoot at 300, 600 and 1000 yards in F-Open.. At 300 yards you could get away with larger E.S.'s... However, once you go to 600 yards, if you have E.S.'s that are in excess of 20f.p.s. you will have a VERY difficult time with vertical.. The excessive vertical will keep you from having scores that will put you in the winners circle. With E.S.'s in excess of 20f.p.s. at 1000 yards is an effort in futility>>period. I have found that once you have a load that shoots nice tight groups at 300 yards but you have less than desirable E.S.'s, try changing primers. If that does not "cure" your problem and you have to start playing with your seating depth and possibly your choice of powder. Changing just the seating depth MAY very well cause your groups to start opening up>>> As Boyd stated, the trick is to get the grouping AND your E.S.'s tight.. Personally, I work diligently to get my E.S.'s in EVERY one of my rifles UNDER 15f.p.s. and I usually end up UNDER 12f.p.s.

 

[dkhunt14]

I know I am going to get negative replies on this but this is what I have found. I have had Dashers that would shoot 2 and 3 ES on 10 shot strings and when shot at 1000 would go vertical. Then had loads with the same gun and 8 to 10 feet extreme spreads and the gun would shoot nice round 10 shot 4 and 5 inch groups at 1000 yard BR. Don't make sense but did it more then once and with multiple guns and calibers. Like the 308 Baer; 6.5-284; 338 Lapua Imp.; 6 Dasher; and 6.5 WSSM. Now the extreme spreads were not greater than 15 and it just didn't make sense. But maybe jim1k, Erik, Donovan and some others have similar experiences.

 

[Erik Cortina]

dkhunt, the difference in accuracy between 2 and 8 ES had more to do with barrel harmonics than with ES. Both ES numbers you talk about are excellent for LR shooting, one just happened to be tuned better than the other.

 

[Erik Cortina]

FTRrookie, your results are a typical example of why I made my barrel tuner, so I could match barrel harmonics to the load instead of chasing my tail trying to match load to barrel.

 

[Lapua40X]

Howdy, FTRrookie. 3 shot groups don't really provide enough information to make final decisions. They can give you a rough idea on where to start fine tuning the load but, once you have a range within which to work, you need (IMO) ten shot groups to really see meaningful data.
Allow me to make a suggestion. Leave the chrono home, select three loads from this test that look promising and run them out to 200. Then, compare the results to your 100 yard targets. I believe you'll see the comparative ratio between the groups to be less than linear. Once you've got something to work with (a fewer number of loads) play with those by collecting MV data and stretching 10 shot strings out to 200 yards.

 

[mysticplayer]

Not knowing your reloading set up:

ensure you have a quality scale that will let you weigh charges UNDER 0.1gr. it matters

bed the action properly

Know that with a factory barrel, 1/2 min on a high volume, and consistent basis is fantastic. 3 Shots into one hole may be the best 3 shots of a pattern that is larger

Test at 200 and better yet 300yds. Any error in your load will be obvious and loads that may not look good at 100yds may shine.

Get some Win brass or anneal like crazy after reducing neck thickness to 10 or 11 thou.

Load around 24.4 would be about right as Lapua is much lower internal case volume vs Win. the 25gr loads are likely too high and tuning will continue to be a pain.

If you are in a cold clime, move to CCI450 primers

If you find shooter fatigue a problem, shoot 3 3rds groups separated with enough time for you to get comfy. If a load is stable, it will shoot. If loads wander, that is a better indicator of the true accuracy of that load. wind flags are imperative.

Load for the smallest 19rds group I have ever shot with a 308 at 100yds wouldn't stay on a piece of paper at 500m.

Good luck.

Jerry

 

[ftrrookie]

Finally was able to get to the range today and being the curious person that I am I wanted to see if y'alls predictions on my loads with the high ES would hold up. Shooting at 300 yds the highest ES load did open up but not as much as I expected. I'm going to shoot the same loads at 600 and 800 when I get the chance (hopefully next week) and see what happens. What do y'all think? Am I chasing my tail here?