So I tested my first batch of ammo today. I wanted to eventually test every variable to see what might matter, and the first measurable variable in my reloading process is the variation in shoulder bump that I get from my Redding Premium full length resizing die. I separated the brass into 4 different shoulder bump measurements and then loaded everything else the same. What I was not expecting to see out of these 80 rounds, that all had exactly 41.0 gr of H4350 out of the Hornady Auto Charge Pro, was such a large variation in velocity with a total ES of 86fps. What is even more confusing is that the individual “bump” group with the worst ES of 72.1, had the best groups! I am including pictures of my data for anyone interested in looking it over and giving me their thoughts.
At short distances like 100 yrds, you are not going to see a big difference in group sizes with large ES. But at longer distances you will see a difference between a low es group and a high es group.
I haven’t cracked the low es code myself yet. I do know a couple of the other reloader sites and video channels I watch swear that mandrel sizing your neck makes the biggest difference. I’ve tried that and it seems to work with some but not others.
Yes, I am worried that once I try to stretch out the distance, my consistency will be garbage because of the ES I am getting. I may have to look into the mandrel resizing and see if that helps. I do want things significantly tighter and more consistent with my loads before I worry about distance though. I just wasn’t expecting velocity to be a large variable today! 
An sd of 15 is equivalent to most factory ammo. It’s not bad. Getting under 10 is tough to do.
A 15fps SD will only account for 2” of average error at 700 yards with a 6.5 Creedmoor at a standard velocity.
With the amount of time and effort that I put into this, I expected significantly better than factory ammo.
Cool. First three things I’d try to get a single digit SD from this point are
(1) Use Federal Gold Medal Match primers. That can impact the SD significantly. Sucks, though, because we all know how hard they are to find. A match primer can sometimes change the SD a lot.
(2) Try Lapua brass. Annoyingly expensive and you already have brass here, but it can make a big difference if you want single digit SD’s. Hornady can be capable of it too, but brass sometimes makes all the difference.
(3) Try dry case lube on the necks. Sometimes this makes no difference, and sometimes it changes everything.
I like getting the most accurate ammo possible as well. Just keep in mind that ammo can be, at the same time, FAR more accurate in a gun than factory ammo, and also have the same SD as factory ammo.
Remember that velocity differences like this won’t even be measurable on target at 100 yards, and only account for about 2” at 700 yards. Not saying to ignore SD. Just saying there are bigger fish to fry right now. Your groups are around 0.95” at 100 yards. If we can shrink the groups to half an inch, that would make about a 50% bigger change to your down range accuracy than getting to a single digit SD.
Do those recommendations improve the accuracy also, or just the standard deviation?
Thanks
If I were going to try and cut down the group size, my top three things to try at this point would be (1) big changes in seating depth such as 30, 60, and 90 thou off the lands.
(2) Try Lapua brass
(3) Test a different bullet
What if Lapua doesn’t make brass for it? (280 AI and 28 Nosler). Currently using Nosler brass.
Thanks
Peterson would be a close second for me. Nosler as well. I don’t pretend your groups will shrink immediately by changing brands, but I do find things to just come easier in load development when using the top tier brands.
Could he sort his brass by weight and water case capacity? Try to find a batch of brass that are basically the same? Fire form in your rifle and then neck size to have same shoulders and case dimensions? Just ideas that might be useful or not.
I will try the large changes in seating depth next. I already purchased some Berger Elite Hunter bullets in anticipation that I might need to try another bullet, and I just ordered some Lapua brass. I’ll update after each step.
Looking forward to seeing the changes. Appears you have a good test procedure so it will be fun to see the changes.
Apparently Lapua changed their packaging and no longer sends brass in a useful case!
At least the 7PRC Peterson came in a case!
I also find that when I double weigh my charges I get better SD with way less spread in my velocities. Your auto loader will never be as precise as a separate scale. Once I did this, I found that my SD went way down. Of course your powder type will also play into this, stick vs spherical…. Got to love chasing these things down the rabbit hole. lol
Not sure what you mean by double weigh.
Thanks
Your powder dispenser weighs it once, and then you reweigh again on another scale and then trickle or remove powder to get exactly the same weights each time. I’ve found that my powder dispenser can be off by .005 to .02 grains load to load. This way when I say there are 55gr of powder, I know it is 55.000 every time. This consistency has led me to have extremely consistent velocities with very tiny SD’s
I considered buying the recommended FX120i from the pro column recommendations, but couldn’t bring myself to pay over $700 just for an additional scale. In the reviews, Jim said that the Autocharge pro had good consistency, so I thought it would be good enough.
What speed are you using with the Autocharge Pro? To get the best results every time, it has to be at the slow setting. With it at medium and high you are going to see a more significant deviations in the amount of powder.
I use the low setting, Speed set at 1.0, and Time set at 0.5.