Extreme spread and standard deviation vs accuracy

[southernfella]

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?

 

[L.Sherm]

At the end of the day trust the target.
I would shot your load at the max intended distance you plan to shoot.

 

[sedancowboy]

Take your best load and adjust seating depth in .025 increments. ELD-Xs like jump.

 

[Reemty J]

RL25 or RL26 better groups more velocity

 

[StumpyJohnson]

I think it's important to know that 3 shot and 5 shot groups can give you just a small peak at total dispersion.

Small sample sizes.

There's a video by Hornady, called "Your groups are too small." It's a bit controversial, but I think there's some truth to it.

Also, I've had similar issues and I find that I usually avoid the hottest loads, for various reasons. At the end of the day never adjust more than one variable at a time and maybe try 10 shot groups.

My 6.5 prc will stack twenty shots into a 1.5" groups at 200yds. It will also shoot 1.5inch 5 shot groups at 100yds. And finally it will consistently shoot 3" groups out to 600yds. Reload for your purpose.

But my sd/es are always low and I think that plays a very important role in my longer range work.

Never used imr4831... But have had great results with h4831sc,n165,and n170. Also, went away from magnum primers due to availability, and I don't think I'll go back. My numbers are better without them.

Make small tweaks and shoot more. Or change a component.


Good luck. LMK if you want my pet loads.

 

[chav0_12]

I think you need to switch powders or something. My 6.5 Creedmoor is almost that fast. Personally, I'd see if the faster load can work by adjusting seating depth. Still need good groups. I'd also keep going until I hit pressure. I'm not sure if you're there yet or not. You might have another higher node that shoots good groups and has consistent speeds.

Word of advice, since you said this is your first load ever; don't jump to what's listed as a max load in a manual. work up to it in 1/2 or less grain increments. I typically will approach a book max at .2 grain increments then proceed passed it at the same pace until I find a good group at a velocity I was wanting/hoping for.

 

[Pilsner]

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?

Hornady recently put out.a.podcast about reloading and gathering data off of 3, 5 or 10 round groups and how pointless it is.
Title of the episode is "your groups are too small".
Basically those groups (and every single called flyer ever shot) are complete and total BS from a statical standpoint for gathering accurate data.

Give them a listen and start over.

 

[cajun]

If your going to shoot those velocities might as well have a creedmoor. Try different powders.

 

[Justice1327]

Hornady recently put out.a.podcast about reloading and gathering data off of 3, 5 or 10 round groups and how pointless it is.
Title of the episode is "your groups are too small".
Basically those groups (and every single called flyer ever shot) are complete and total BS from a statical standpoint for gathering accurate data.

Give them a listen and start over.

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.

 

[Phil Rizzo]

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?

If those groups are at 100yds that's fine, but you will gain confidence in the stability of acceptable groups at longer ranges. Try 300 but the farther out you go the more you learn about the load.
Sometimes the tightest ES/SD isn't the one that groups the best. But it's cool to see consistency, and likely means you aren't far from where you want to be. Good luck to you.
I like ladder tests at 300 and 500 is better.

 

[Hugnot]

This is of interest to me.

I did a copy-paste of the data so I could play around with it.

 

[FEENIX]

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?

Yes! Most would do a ladder test as a baseline to develop from. Take your time and pay special attention to the consistency of your loading processes (neck tension, powder charge, seating depth, seating depth, etc.). There are many references from people with far more excellent knowledge and experience than I have to resolve the spread and SD first. As others have noted, with a 6.5 PRC case capacity, you should be getting higher velocities than what you are getting, even with your IMR 4831 powder choice. Good luck!

 

[JTH]

If your going to shoot those velocities might as well have a creedmoor. Try different powders.

I could be wrong but IMR 4831 is likely a little fast of a powder for the 143. Check out the Hodgdon reloading data center, see what they recommend. With the 143 in a 6.5 PRC you're in the H1000 to Retumbo range for powder. Other comparables would be Vihtavouri N570 or N568, Alliant RL26, letc. This would get you closer to case fill and hopefully get the speed up, those velocities are pedestrian for 6.5 PRC with a 143. I'd suggest searching this site for load data on the 6.5 PRC and 143, you might get a head start and save yourself a bunch of time.

If you're set on the powder, go to a lighter bullet, something in the 120 to 130 class is probably more appropriate for that powder.

With this being your first load ever, thought I'd share what I normally do. Others may disagree, hopefully this helps.

After I've selected the powder, start on the low end. Seating 0.020 off the lands run a test to find pressure, going up 0.5 grains at a time. Monitor velocity on all of these looking for a node, but also shoot all of these rounds at the same spot, looking for consistency in poi and note any changes. Stop when you hit the max load, or find pressure, whichever comes first.

Then I pick a charge weight to start developing from that data (based on consistency of poi and velocity), and start testing seating depths, backing away from the lands 0.005 or 0.010 at a time, 3 shot groups. I've not spent a lot of time with the ELD's, but most bullets have a range of jump from the lands that they prefer. See if you can find that info to save yourself some time and components.

When I find the best seating depth, I come back to the powder, do an OCW test at a minimum of 200 yards. Loading in 0.3 grain increments over a 1.5 to 2 grain range around the node to find the right powder charge. This usually gets me well under MOA.

However, sometimes a barrel doesn't like a powder/bullet combo. Learning how to identify this early on and move on to other options can be a challenge.

I'd also add that consistent neck tension is very important in getting your es down and improving your groups. Make sure your cases are chamfered and deburred. Lube the inside of the necks. Some bullets have a sweet spot for neck tension, I'm usually running 0.025 or 0.003 for best results. Hard to believe that 0.005 in NT could make a difference, but it definitely can. Time spent on these details pays off

 

[sable tireur]

From the Hodgdon reloading center:

Note that all loads except two are COMPRESSED loads.

Ramshot Magnum and VVN-565 are nearly perfect in density and performance.