Extreme spread and standard deviation vs accuracy

[SmokinCrow]

According to their advice, one could shoot out a barrel before you had enough data to make a decision. Secondly, if what Big Red says is true…how come their are thousands of high quality successful shooters who get enough data from their limited sample sizes to be "Top Guns?"

Yes, I have seen the podcast. My take away is this. Dont think you have a successful load after 20-50 rds down the tube. Shoot 100-150 rds and then make a decision.

That's not what they said. For true statistical significance you need 35 shots or there about. After that they didn't see statistically significant change. And they tested 50, 100, 250 shots etc.

They said they pick a charge about 1 grain under max and shoot 20. If in 20 you're not shooting something that's sufficient you already know it's not going to work for you. If it's working 35 will give you best statistical data to know the load. If after 20 they would change things. Powsder or Primer generally made biggest impacts. Lower charges showed less dispersion which is why they basically picked the charge under max. They said depending on how the load shot you would definitely know even by 10 shots if it wasn't going to work.

I had my doubts about their method, but I tried it, and I haven't chased my tail finding variations between shooting days as when I loaded 5 shot ladder teats. And going back to verify etc. not saying it's the only way, but it worked for me and has helped make a difference. Thinking statistically just made sense to me, they alsosaid if something works for you great. Just sharing what they had found

 

[Stonyman88]

Hey folks, I'm working on my first load ever and and running into an interesting problem I can't seem to find answers for.

I started with 3 loads out of the Hornady reloading vol.10 book and the very first group of 5 was touching, the second group of 5 had 4 almost in the same hole and one flyer that made the group almost 1". I'm shooting 143gr ELD-X out of a 6.5PRC savage ultralight with the proof carbon wrapped barrel.

Chronograph only caught 4 of 5 and didn't work at all the first group 51.6gr IMR4831

2774
2788
2797
2750

BUT when I tried a hotter load with the most consistent velocity out of the 3, it gave me 1 inch groups both times. 52.7gr IMR4831

2892
2885
2885
2886
2883


2876
2874
2877
2877
2905

I'm totally stumped. I'm thinking building a ladder off of the first load to try to minimize es and SD, is this the right course of action? Or do I build off of the one with consistent velocity and hope to find a node there?

After you boosted the load up, One thing, did you use the same 143 ELD-X SEEDS, number two did you mess with seating depth, I have the same results until I worked with seating depths. Mine shoots the H 143 ELD-X the same, and they are at least on my testing from the factory ammo were set around . 60 thou off the lands. If you monkey with the depths from 10 thou to 60 thou at 5 or 10 thou jumps to start you'll see what depth shoots the best. The Hor..... shoot great for me right out of the boxes. Shoot 3 shots then seat the next and shoot them and so on. you'll see the groups tighten up I'm sure. So I seat mine the same as factory loads, unless I boost the loads up.

 

[PatriotHenry]

RL25 or RL26 better groups more velocity

Or H1000

 

[Stonyman88]

Or H1000

I agree very much, RL 26 or H1000 are super

 

[Mike6158]

I've tried one shot ladders, 3 shot groups for ladders, and 5 shot groups for ladders. I'll stick with 3 shot groups. I don't pay attention to SD anymore. If you look up the calculation for Standard Deviation, while simple, it's clearly an equation for large samples.

ES tells me what I need to know. The one shot ladder was interesting and I will try it again on a rifle that I've never developed a load for.

 

[Csbc4fun]

H1000 is much easier to get.

 

[Mike6158]

H1000 is much easier to get.

I like H1000 and I have "a bit of it". I am going to try another load test but I switched to Reloader 25 in my 7mm Rem Mag and I got better accuracy and worse temp stability.

 

[Csbc4fun]

The one shot ladder is to get basic feet per second data and to find pressure signs. Then I select a powder charge from that data and load 30 rounds or more seated at the longest seating depth. I take my press to the range with seating die, clamp it to the bench and seat three, shoot three until I find the best group. That way if I screw up a group I can try it again and at the end not have any rounds seated deeper than I want.

 

[Tech4]

I start 1.5 gr blow max and increase by .2 gr until I hit max or high pressure and shoot one shot at each charge weight. I test velocity at the same time. When I am done, I have an 8 shot group. If it is a good powder bullet combination it will be a small round group if not, I move on to another powder or bullet. I look for where the velocity is the most stable and load 20 at that charge weight and if the accuracy is good, I will shoot groups 200Y 300Y 400Y and if I am getting half MOA I call it good. Doing it this way I am not wasting a lot of time on the wrong powder, bullet primer combination. I have to load to mag length, so I don't mess with bullet seating depth that much.

 

[cajun]

I start 1.5 gr blow max and increase by .2 gr until I hit max or high pressure and shoot one shot at each charge weight. I test velocity at the same time. When I am done, I have an 8 shot group. If it is a good powder bullet combination it will be a small round group if not, I move on to another powder or bullet. I look for where the velocity is the most stable and load 20 at that charge weight and if the accuracy is good, I will shoot groups 200Y 300Y 400Y and if I am getting half MOA I call it good. Doing it this way I am not wasting a lot of time on the wrong powder, bullet primer combination. I have to load to mag length, so I don't mess with bullet seating depth that much.

I started doing this during the previous component shortage. If you have an accurate load you see it quick. If you have a really accurate rifle you may need to shoot the ladder at longer distance. My creedmoor with 140 eld and H4350 put 8 shots over 2.5 grains sub moa.

 

[StumpyJohnson]

Seating depth has more to do with group size than powder charge in general. What are you doing to ensure consistent neck tension? Using a mandrel expander die will solve a lot of inconsistencies.

I would tend to disagree slightly with this, I'll conceded that consistency in the reloading process is of the utmost importance. However, I typically see bigger changes as a result of powder than seating depth, all things being equal. And I went down the mandrel route with varying success.

I'm betting that PNWdude67, has roughly 10 more years of experience (which counts for more than my observations), BUT...I've been getting great results from hornady's ~$100 Match Grade Die Sets. Believe it or not. I put the appropriate bushing in and leave the expander mandrel on...Now I know I'm slightly overworking the necks possibly, and I know that its heavily dependent on brass thickness.

Maybe I'm lucky I guess, but I'm getting roughly .0035 neck tension and nice concentricity. Again it could be luck, but the last 3 caliber's I picked up have all done well with this method. I have a pile of expensive dies and mandrels and bits that lay idle now because of it...but hey its been working. The side benefit is lower costs and a simplified reloading process.

1. Tumble brass.
2. Lube and size with decapping pin and expander button on.
3. Tumble off Lube
4. Clean pockets
5. Trim and Chamfer with the Forster Trimmer in one go.
6. Charge, Seat, Shoot.

 

[SSG Graybush]

This has worked for me…

Step 1). Load 1 each (2,3,5,10 doesn't matter much) powder charges at 0.3 to 0.5 grain increments at the closest seat depth to the lands that you will run. Shoot at any distance as long as you do not shoot at a target (do not look at groups) and record velocity up the ladder until you DO see pressure signs (smudge on the back of the case, heavy bolt lift, black smoke around primer, etc…). Graph out the velocities. There will be a node, flat spot, a place where the velocity increased less than the other increments.

Step 2). Choose a powder charge in the center of that node. Load that powder charge, 3 each at seating depths 0.003" increments for a total of at least 30 rounds. Shoot them slowly and carefully at a target set at 100 yards. Select the best group.

Step 3) Now using that seating depth, load 3 each with powder charges in 0.2 and 0.4 grain increments up and down From previous load. Shoot at 100 yards, select the best group.

Step 4) Shoot another 2500 rounds at that powder charge and seating depth. Purchase a new barrel and repeat Steps 1 through 4.

Have Fun!

I do this as well, but I start at what I've found worked for certain bullets in the past, for jump after initial latter to find starting charge weight and max. For Bergers I test 60 to 75 thou jump, Nosler, Seirra and Hornady 5 to 25, Barnes 45 to 60. And I never jam, few times I tried it it gave good results but not the best.
2500 rd barrel life, maybe if you only shot 308's.

 

[nksmfamjp]

Take the first load, load 10, shoot those into 2 5 shot groups. Determine average group size between all 3. I'll bet it gets better.

I would also consider maybe a seating adjustment if that flyer keeps showing in all 3.