Home Forums Hunting & Shooting Ask The Gunwriters SD and ES

Been doing more reading on SD and ES in a load and why you want them to be low. Makes sense.

I'm wondering what you all consider to be "low" for this number? That is - if a guy gets to 10, consider that good or is good actually 7 and great 5 - so to speak.

Where do you like to be? Is there a floor where you'll just never get under?

There will be much said on this thread.

What I will state is that almost every last time I was shooting at 600 yards and watched the chrono the load that produced the lowest ES and SD and then went and looked at the holes in the paper I was never happy. The lowest ES and SD just never produced best accuracy.

That said nothing wrong with low numbers. In fact they are good.

But it changed my attitude totally. Run the chrono sometime so I know what ballpark speed.

But test ammo at a far distance and go by how tight repeatable groups are. Looking for weird flyers to indicate IFFY load. And watching for round groups as a whole. Got to where I played mostly with primers and neck tension and pretty much ignored the chrono and paid attention to actual groups.

What we found is you can have low numbers and bad groups. Or you can have decent numbers and good groups. I know what I want.

And add in seating depth to what rost said

Those are great points from experience.

ES and SD don't account for barrel harmonics.

I've read where some find the best ES (lowest) and then adjust seating depth to get the best group out of that ES. Is that real/fake etc - this is coming from F class guys.

Only fire 3 shots so you can claim single digits on both to be impressive.

HA! (But know guys who take it seriously....)

I'm a 5 shot guy and honestly, I understand that for most of my life, 100 yard sight in and then go hunt out to 250/300 with little struggle but my interests are starting to stretch out and I realize finding an "accurate" load for that typical deer hunting isn't hard and it starts to matter a lot more past those ranges. Why I've started looking/poking around guys like Cortina and F-Class John on such topics of load development.

Just hoping to get a good cabin fever discussion that's beyond "Creedmoor doesn't do anything XXXX doesn't do" type of discourse.

I tweak for consistent pressure/speed by adjusting powder type and charge weight, consistent neck tension, primer ignition, etc., and then adjust seating depth to time bullet release at an anti-node in the harmonic motion of the muzzle. That gets both low velocity dispersion and low POI dispersion.

To answer the question in the OP, sample size matters. Statistical quantities like SD and ES are only really meaningful if the sample size is large enough. Typically, a sample size of 30+ is where we start to associate some weight to variance metrics like SD. If you take a sample of 30 shots and the SD value is less than 10, that’s very good.

I`ve never done that numbers thing, and I`ve loaded thousands of rounds of match ammo. Mostly for the 308. I find a load that shoots well at one and two hundred, either with the match gun or hunting rifle, and go with it. I then concentrate on what I`m doing, couse I do f`up now and then.

Sometimes we make this loading stuff way too complcated.

Yep, a minimum of 30 is what a major American ammunition factory uses when working up loads with a new batch of powder.

👍👍👍👍

Seems that this is usually left out of the mix, or has been in most discussions on this subject.

Absolutely, larger the sample size the better and I agree. Good reason to shoot more.... which probably isn't a bad thing.

So assuming a large enough sample size to be relevant - what's the final number you want to see? Sub 10 or?

That could work. I've never tried it that way.

Seating depth was pretty much a given for me. Same barrels, same chamber reamers etc... and at that point I knew where it should be. And playing with it never really changed much.

That said I never went back to the lowest ES and played after that.

I don't waste lots of shots proving anything anymore. Especially since I'm not competition anymore. There I needed to know if things were good with 20 shot groups...

But what I do is continue to shoot what I pick at the onset, at various yardages.

One of my favorite things the last years is since we have been playing the BDC sig scopes, take a 3 inch diamond target. Put it up. Shoot one at somewhere around each of the 100s... out to 500 or 600. And see if I can keep all 5/6 shots in the 3 inch bull. I can do it most of the time. It verifies day in and day out that the load is solid.

Really for me, it goes back to the Audette. Get in the middle of the highest MV node and that should serve probably 95 % of peoples needs

Yeah, an SD of less than 10 fps is my target.

Tell ya what try putting 20-25 rounds into a 1.5” circle at 300 yards instead of deer hunting accuracy. It really isnt that easy as people think.

As a function of shooting ability or as a function of actually being an accurate load? - that's the point. Eliminate the variable and do the best you can while building the load. I'm trying to learn what does/doesn't matter with the load and to a degree then - what's the target for those data points to indicate, I've found the load - now work on the idiot yanking the trigger.

Great topic.

+1

dave