[just_me_mongo]

My three cents:

FPS
You used the method in which you increased your loads by .2 grains. That is a win!
Shot # 8 produced 2508 FPS (28gr). Shot #9 produced 2504 FPS (28.2gr). The difference between the two is 4 FPS. I would have no issue with loading up 9 rounds of 28.1 grains (right between 28.0 and 28.2). Shoot 3 - 3 shot groups at 100 yards. Measure your groups.

Brass
Split case necks are a sign of hardened/overworked brass. I see this at times with my 5.56/.223 brass. I would throw them out and be done with it.

Primers
The pictures do not show me anything alarming.

Shoulder Bump
.003 +/- sounds good to me.

COAL
2.285 +/- sounds good to me.

Bottom line: your results look really good to me. I think you are overthinking this or being too hard on yourself. I LIKE THE DATA.

TC

 

[Jellysick]

@just_me_mongo - You mentioned about shooting a string a few posts back with the intent to look at ES. I know what ES and SD are in relation to chrono results, but I'm mulling over their use. Correct me if I'm wrong, ES and SD speak essentially to the quality and consistency of a load. The smaller the spread, the more consistent, etc... The larger the spread, or more variation... isn't this a factor of less accurate reloading methods (i.e. a powder thrower that is inaccurate, or seating the projectile inconsistently from round to round)? Or are what we looking at with ES and SD characteristics of a given load vs one of a different charge (i.e. 19.7gr of something versus 19.9gr of the same powder)?

Asking simply because it is easy to get wrapped around the axle with the amount of data that can be collected and analyzed. If one of my 300BO loads has an ES of 50 (or whatever), I'm not sure I care..? Sure the drop at 400 yards will be significant, but it'll never be used in that scenario, hence why (at least I think?) it doesn't matter.

 

[Strawdawg]

No matter what distance one is shooting over, the more consistent the load performance, the more consistent the accuracy. Some times a small change in the loading will make the difference between a two inch group at 100 yds to a half inch. No matter what, we want the performance consistent if we are hunting, or trying to hit the target the best. I am not a precision shooter, but, since the Chrono gives us the data, I generally look for the best numbers but I don't obsess over a 20 fps variation, or even something more variable, say 40 fps as long as there are no flyers in the numbers. It's not a big deal to look at the numbers along with the primer condition and velocity change as the loads increase. If I were a long range participant, I would.

I'm looking for relative consistency without stressing.

 

[Jellysick]

No matter what distance one is shooting over, the more consistent the load performance, the more consistent the accuracy. Some times a small change in the loading will make the difference between a two inch group at 100 yds to a half inch. No matter what, we want the performance consistent if we are hunting, or trying to hit the target the best. I am not a precision shooter, but, since the Chrono gives us the data, I generally look for the best numbers but I don't obsess over a 20 fps variation, or even something more variable, say 40 fps as long as there are no flyers in the numbers. It's not a big deal to look at the numbers along with the primer condition and velocity change as the loads increase. If I were a long range participant, I would.

I'm looking for relative consistency without stressing.

I do understand that much. But I'm trying to figure out what contributes to good or bad numbers, in terms of ES and SD. If I load 19.7gr of something and get an ES and SD that is unacceptable, is this a function of that particular powder reacting inconsistently with a particular bullet weight and/or seating depth in my barrel? If unacceptable ES or SD is noted, is that an indication that the particular charge weight is not ideal or is it simply an indicator that some variable needs to be tweaked to dial it in (COAL, charge, crimp, etc)?

 

[just_me_mongo]

@just_me_mongo - You mentioned about shooting a string a few posts back with the intent to look at ES. I know what ES and SD are in relation to chrono results, but I'm mulling over their use. Correct me if I'm wrong, ES and SD speak essentially to the quality and consistency of a load. The smaller the spread, the more consistent, etc...

Long/short: They speak to the accuracy, consistency, and quality of the load.

The larger the spread, or more variation... isn't this a factor of less accurate reloading methods (i.e. a powder thrower that is inaccurate, or seating the projectile inconsistently from round to round)?

Not always. You can have great reloading methods and still wind up with poor accuracy. What you mentioned above seems more along the lines of barrel twist, bullet weight, powder, and primer combos. Poor/less quality reloading methods can still produce tight groups (I know because I've done it).

Or are what we looking at with ES and SD characteristics of a given load vs one of a different charge (i.e. 19.7gr of something versus 19.9gr of the same powder)? This takes an explanation so please follow my example which I made up for teaching purposes.

Load #7: 19.7 grains produced 2775 FPS. Load #8: 19.9 grains produced 2777 FPS. The difference between these two loads is 2 FPS. I would then load 19.8 grains because it is directly in between load #7 and load #8. There is a purpose for using this method. I would take 9 rounds of 19.8 and shoot 3 - 3 shot groups at 100 yards. I already know from the numbers in FPS that this load will group well. I also know that it will do better in temperature rises/drops and I would have no problem zeroing this load. You can go much farther down the rabbit hole if you so choose.

Rabbit hole: you could load up 20 rounds of 19.8 grains and shoot/chrono all 20. Then you would be looking for ES/SD. Whatever the number, you could then start playing with the COAL to fine tune your group. You start going down this rabbit hole if you want to shoot well at 600 yards (accurately & consistently). That rabbit hole is so deep that you will not believe.

Asking simply because it is easy to get wrapped around the axle with the amount of data that can be collected and analyzed. If one of my 300BO loads has an ES of 50 (or whatever), I'm not sure I care..? Sure the drop at 400 yards will be significant, but it'll never be used in that scenario, hence why (at least I think?) it doesn't matter.

Strawdawg stated it very well above. Long/short: we want accurate, consistent, and quality loads because we are hunters. One shot: one kill.

I recommend that you read this article:

Long Range Shooting: Understanding Extreme Spread And Standard Deviation - Guns and Ammo

With the increase in interest in long-range shooting, the terms extreme spread (ES) and standard deviation (SD) are being thrown around a lot.

www.gunsandammo.com

TC

 

[Strawdawg]

It's really what you are satisfied with in the end. But, understand that no two barrels are exactly bored/chambered identically altho some may be closer than others. Then, throw in climatic conditions, elevations, etc. What works at 90 degs and 200 ft of elevation, and a given barometric pressure, etc may not work the best for you...and of course, I think, some powders are much more temperature sensitive than others so the pressure created on a 90 day may be much higher than what the same load produces on a 40 deg day.

If there was no affect from such things, we could easily pick a load from the manual and all be similar. We usually pick some load and work from there to find the best performance for our gun in given conditions. Some loads are more consistent than others but still, if we want to improve the performance, we experiment with powder, load, length, and so on. Just because Xman has the best results from his gun, in his area, under certain conditions, does not mean you would received identical performance due to the various things I mentioned in the first paragraph.

ES and SD are merely a couple of tools we use to measure performance. Velocity and accuracy are just as important but comparing performance at 5000 ft elevation in the winter may not be the same as what would work for me at any time. That is the reason we see what works...and then we also consider brass life, etc which may be difference between two different people. One may be happy with three reloads and another may be looking for ten.

There is nothing to obsess about unless one has an end goal that requires more perfection to obtain it.

I suspect most of us are looking for a load that meets our own needs year round in our area with our particular gun. Only the loader can determine what makes him happy.

 

[just_me_mongo]

"I do understand that much. But I'm trying to figure out what contributes to good or bad numbers, in terms of ES and SD."

For your testing, what contributes to good or bad numbers is your powder charge. Take a look at one of your spread sheets and see how each powder charge changes the produced FPS.

TC

 

[Strawdawg]

Standard deviation and Extreme spread are simply measurements of variation and are often applied to manufacturing processes and such as a measure of quality control. Lower the numbers, the more consistency we are seeing. The numbers become more reliable as the sample increases so shooting three rounds is probably not giving you the best number.

Case volume is another variable. Normally we specify numbers are for a given brass as volume is not the same from brand to brand. Also some brands are more consistent than others.

At times, we may find the best SD and ES in powders that produce lower velocities than we might desire. It's just something to try to measure the repeatability of our loading process from case to case and is not necessarily a sign of the ultimate load for our given round.

 

[BoilerUp]

@just_me_mongo isn't this a factor of less accurate reloading methods (i.e. a powder thrower that is inaccurate, or seating the projectile inconsistently from round to round)?

I'll take a try at this. Assuming very consistent and accurate reloading methods, you will still get varying SD / ES from different load combos. Among the variables you can change (primer, power selection, powder charge, case, neck tension, bullet, bullet seating depth, etc), each can vary the quality/consistency of the ignition of the powder, the resulting pressure curve, and the resulting muzzle velocity. I believe the barrel harmonics will drive a lot of finding the best velocity for a given bullet, the other factors can also help get a nice consistent (repeatable) result. Note that the guys shooting longer distance tend to care about this a lot more because those inconsistencies will be more obvious on target 1000+ yards out. They also tend to care more about the vertical spread on the target than the horizontal. For 300 BLK, you don't really need to obsess over it, but it is data worth noting. Also, I recall seeing a video that ES tends to be inconsistent as your sample size grows, so be careful chasing ES because you may never catch it.

Separately, yes, if you are horribly inconsistent in your reloading methods, you should expect that to show up in your STD and ES metrics.

 

[Strawdawg]

I am not sure about ES being inconsistent but, let's face it, you are shooting a blackout. Not much counts past a 100 yds so the theory is one thing, but it may not make much difference as you have already noted.

I would concentrate on more mundane things such as using brass that has the same length, similar volume after sizing. Getting the bump to .003"-.005", finding available powder in the right burn rates and that burns cleanly. Your predecessors have probably done that many times already to you really don't need a lot of powder experimentation. See what is shooting the best for the crowd and play with loads and overall lengths to see what YOUR gun seems to like the best if you want to fine tune to your chamber/barrel.

Don't over think the process and take the fun out of shooting. Work on refining your aim and consistency so that your personal performance does not blur your experimentation results. Take a break when you are getting frustrated. Shoot something else if you have the option. If you can afford it this soon after Christmas, build a different upper in a different caliber. If you have a significant other, buy them something to make your future easier LOL