What to do when SD/ES doesn't align w/ groups?

[arm017]

So I have watched a few hours of youtube on load development and many different techniques from OCW/ Ladder tests/ OBT.
I have resonated a lot with 6.5 guys load development series, and really like their methods they detail. But after a few different barrels and different calibers, I have come to a cross roads on a few loads:

Assuming my handloading technique is optimal and consistent, what do you do when your group size does not match the SD/ES data?

 

[morganlamprecht]

play with seat depth

 

[arm017]

play with seat depth

So you're saying choose solely off of numbers? Assuming that handloading is 'perfect' / consistent (down to the kernel, neck tension uniform, concentricity accounted for, etc. )

 

[padom]

What he said...

SD has nothing to do with group size...after finding your load you need to do a seating depth test to shrink group size...

 

[Sixfivesavage]

Ended up being being neck tension for my load. I think 90% of sd/es can be attributed to case capacity inconsistency, neck tension or seating depth. If you're using decent brass from the same lot, the first is almost eliminated. The rest is primer selection.

 

[arm017]

What he said...

SD has nothing to do with group size...after finding your load you need to do a seating depth test to shrink group size...

So padom, you would recommend just choosing based upon the SD/ES numbers from an accurate chrono and adjusting seating depth / neck tension to tighten groups?

 

[padom]

No I would not. I would recommend following Dan Newberry OCW and choosing the center of your node based off similar POI while also observing chrono numbers to help identify that center then doing a seating depth test to shrink group size

 

[padom]

Ended up being being neck tension for my load. I think 90% of sd/es can be attributed to case capacity inconsistency, neck tension or seating depth. If you're using decent brass from the same lot, the first is almost eliminated. The rest is primer selection.

SD has to do with nodes, and neck tension IMO... with much testing seating depth has no play or very very little in SD's...I shot a seating depth test just last week with a PVA barrel I was testing for them. Loaded 5rds each from touching to .02 off in .005 increments after I found my node. All shot over a Labradar. SD over those 28rds of varrying seating depths....5.3

After identifying my optimum seating depth I loaded up 30rd and shot them over the Labradar. SD dropped to 4.5....

 

[The King]

He might not - but I do. I do a lot of neck tension work to make that stuff consistent, including using graphite lube on my bullet bases.

Some even use a seating tension gauge which I hear is useful.

So padom, you would recommend just choosing based upon the SD/ES numbers from an accurate chrono and adjusting seating depth / neck tension to tighten groups?

 

[arm017]

Can you clarify?

Are your groups good but your SD/ES bad or the other way around and what distance & variance? If you just need a tiny bit of tightening up it might be seating as pointed out. If it is relatively large, you might have a node issue (assuming you didn't do anything extreme with jamming or jumping)

To simplify, SD/ES is the load itself and all that goes into your case prep. The node is a harmonics issue at the particular barrel timing (speed) of that load.

If you get great SD/ES; but crappy groups and you are capable of shooting tiny groups.. You need to change the fps (timing).. Usually if you have a scatter node, thats a good thing because you have identified the charge weights you want to stay away from. If your at the hot end of the load already, go a full grain down and see what happens to your group.

edited to add - I didn't see the above when I started to post. I believe we are saying the same -

Yes- I am feeling pretty happy with my reloading technique. All of my 5 shot group will yield single digit SDs and ES under 20, BUT my issue has been that some of the groups with an SD of 2 (five shot string) will give me looser groups in the ~.5s" as compared to some of the loads with and SD of 9 that will yield tighter groups in the ~ .2s".

So that's why I started the thread for advice on how to move forward as I am capable of nice groups.

 

[The King]

So look at downrange accuracy as a factor of group size vs trajectory variances. An SD20 Group at 1/4 moa will likely shoot less good than a SD2 Group at 1/2 moa.

 

[arm017]

Sorry for so many questions but is the load the same in the groups that are in the 2s and 5s? With such small moa , I assume your at 100 eliminating as much virmem

If so is the velocities slightly higher with the height SDs

No I really appreciate it! I am running a modified OCW test of .3 grain increments of powder (5 shots of each). Yes being done at 100 yard bench w/ labradar. I will take a picture of an example target when I get home to show what I am talking about.

 

[arm017]

That’s the same way I do it; blending both the harmonics that show up close and the chrono that simulates the ladder.

I focus on the smallest group that’s in the middle of the exact same POI. The shift in POI is really the thing to look for, sometimes it is very small.

Your sampling is so small it is hard to do more than that. Once you can load more rounds you may find out that the 5 rounds that yielded X SD is now different.

Once you have the charge weight you can play with seating to tighten the group slightly. The seating should not really do more than effect the run in to lands. That’s assuming your doing so within reason.

Yeah I guess that is my predicament - of what to do when the numbers (SD/ES) don't match with the group. Here is an example of one for 6.5 CM from last week:

 

[BLKWLFK9]

Yeah I guess that is my predicament - of what to do when the numbers (SD/ES) don't match with the group. Here is an example of one for 6.5 CM from last week:
View attachment 6869486

What bullet and length barrel? With those speeds, you have a whole other node that's faster and is as accurate. start at 41.5 and work up. You'll find it. I bet it's between 41.7 and 42.2. Probably dead on 42.

 

[arm017]

What bullet and length barrel? With those speeds, you have a whole other node that's faster and is as accurate. start at 41.5 and work up. You'll find it. I bet it's between 41.7 and 42.2. Probably dead on 42.

It is on a 24 " RPR 6.5 CM factory barrel w/ HRDY Brass, H4350, HRDY 140 ELDM. I am asking more in generalities and using this picture as an example- since I have gotten this situation a few times. I have worked this same load past 42, but just wanted everyone's opinions on essentially the mindset of settling on a charge when your data points contrast each other.

 

[arm017]

The issue we have on this side of the computer is seeing the full set of groups and you POA/vrs/POI that shift is really the key and should be your main focus.

what is important is to have all at a clearly identifiable POA, then the POI vrs that for each load.. you see a bunch that kinda all look the same then at some point the group start to move and eventually have a noticeable offset. you never want to be on the edge of that move regardless of group size. Mostly because heat, cold and reloading variance can bring you to the ofset

That's helpful info - accounting for variation in POA/POI

 

[The King]

I’ll share my method:

1. Load the ammo with graphite lubed bullets.
2. Get seating depth from internet. Pick one. It hasn’t mattered in my process if it was factory ammo coal, or 10 off the lands or some other starting point. I just make sure I’m not jammed in the lands.
3. Load the OCW test. I use the .7% growth number closer to max and start 6% down from max. 1% down near the bottom
4. Figure optimal charge with ES and SD analysis added to the mix.
5. Pick an SD below 8 with lower pressure signs in a good spot in the OCW node.
6. Run a seating depth ladder from there with .005 depth differences to tighten groups.

This has resulted in ammo with an ES of 8 and SD of 4 in both my 6.5 SAUM and my 6.5 CM. Both loads Group sub .3.

I found my 57.8 load grouped great, had SD of 4 and had zero pressure signs. It was only 10 FPS slower than the atomic hot 59.4 load that was on the other node.

I was able to get an ES of 1 out of the Oak Ridge-hot load and cried when I had to give it up.

 

[padom]

We are also talking 5 shot samples which NEVER tells real SD and is just an indicator...Shoot 25rd of each of those 2 charges and you will get more realistic SD's... I wouldn't worry too much about those numbers and worry more about POI and being in the center of a node. People get too caught up on group size all too often and don't choose loads in the center of a node. After you picked center of a node based of similar POI's then seating depth test. There is where you choose the smallest group. Then load up 25rds shooting all them over the chrono at distance (300 and 500yd is what I do) to get final SD and performance at distance...

 

[The King]

I stopped at 15 rounds on that load. Chrono was a labradar- it only recorded 14 traces.

It was obviously over pressure despite not being as hot as most people get out of the SAUM. 59.4 of h1000. Blew 4 primers and nuked the pockets on the rest of the brass. I too was amazed when I saw the ES was 1. I chock it up to dangerous overpressure levels and wonder if the primer failures acted as a pressure relief function to level the ES out. Every primer was smoked...

Oh brother, I’ve been in
The ELR game a long time, were ES matters.. and never seen such claims of any meaningful round count.

With this, I am out -

 

[morganlamprecht]

We are also talking 5 shot samples which NEVER tells real SD and is just an indicator...Shoot 25rd of each of those 2 charges and you will get more realistic SD's... I wouldn't worry too much about those numbers and worry more about POI and being in the center of a node. People get too caught up on group size all too often and don't choose loads in the center of a node. After you picked center of a node based of similar POI's then seating depth test. There is where you choose the smallest group. Then load up 25rds shooting all them over the chrono at distance (300 and 500yd is what I do) to get final SD and performance at distance...

this, a 5 rounds string at 100 yds is hardly anything to worry about your ES/SD...especially in the pic posted that has an ES of 12 and 18...too close for only a 5 round sample to be proof of anything

 

[BLKWLFK9]

?? what does that matter in a OCW run?

It doesn't.. I was looking at his velocities. They are definitely at the low end if it were a 24" barrel, but normal if they were through a 20"

 

[Graywolf.260]

If you are shooting 100 yd groups, it takes a large ES in velocity to change point of impact. Check with a ballistic calculator. Barrel harmonics has a much larger potential effect.

 

[Greg Langelius *]

After a couple of decades of working at load development, I no longer even take out the chrono anymore, because it has become abundantly clear to me that small SD/ES numbers have absolutely no bearing on where the barrel's harmonics determine the sweet spot.

I.e., 'good' numbers can occur at charge levels that deliver a charge that's far from an actual harmonics accuracy node.

IMHO, the only reliable indicator of a good charge level is the target.

Greg