Scott satterlee

[Ledzep]

...

Newberry’s OCW has been shown to produce accurate repeatable loads. by shooting round robin and looking at loads that have similar POI, it attempts to identify aa load that is insensitive to minor changes primers, charge weight and case vol/prep. It is quantitative in nature. Once a node is found, as you state, it must be verified as stable by additional shooting. It tries to minimize outside factors that effect accuracy in testing such as wind. Unfortunately, the primary source of error in the method is the shooters ability. This is true with any method that relies on a human for operation and a target for analysis.

Showing insensitivity to "minor changes in....." relies on the assumption (unless you have data showing otherwise?) that there is sensitivity in minor changes in those variables.

Here's 20x each of the same load (6mm ARC 110 A-tip w/Varget) with 3 different primer types, all else the same. SD for each test was within 1fps. Avg MV for all 3 was within 6 fps.

Everything I've seen with powder ladders is that if you're changing charge weight less than about .7-1.0 grain increments, you're unlikely to see any meaningful performance difference. All this is why everyone's chosen method seems to show great results-- because it all works.

Obviously there are exceptions, and there are combinations that shoot like poopoo, but so long as you pick a bullet your barrel likes and a powder your barrel likes, you can do whatever confirmation bias funnel load development you want and end up with a great shooting combination.

 

[Rockdoc173]

Hey OP, why didn't you just ask which is better, 9mm or 45ACP? lol. I have spent a lot of time trying both methods, the "Satterlee" method and OCW. Satterlee is nice because you just go shoot over a chronograph, you don't have to worry about a range, shooter error, or other externalities effecting the final load you shoot. However, while I think most things in life can have a mathematical doppelganger, there's usually more that can be learned outside of hard and fast math. So, while you may find a load with super low SDs, it doesn't necessarily correspond to a solid load that will stand up to differential environmental factors, component lot variances, etc. Take benchrest guys, they were producing disgustingly small groups long before chronographs so a good SD wasn't what they were after. The two are not always different, but they're not always the same either.

Second, I talked to Newberry about his method once and I don't recall him ever mentioning SDs, certainly not as the prime factor in load choice. That is not the metric by which all his loads are judged. However, the Ko2M guys live and breath SDs in the 2 to 3 range, so they do. Thus, I thought to myself, there must be a very real need for a low SD and mathematically I understand why. I just didn't see good SDs translate to good groups all the time. Now, if SDs are not the big dog in the pen (I've already pissed a lot of dudes off with that), what is? My answer is that both group size and SD (and ES) is important. My go-to procedure now is to shoot an OCW test and then choose the loads with the lowest SD, or thereabouts. Complex, right?

Recently I did this for a 6 CM load. Using 110 ATips and H4450, I made loads from 40.8 to 42.3 in 0.3gr increments (N=6 loads), then identified what I thought was the OCW. I tallied the SD and used that to solidify my decision. That's it, I didn't even need to fiddle with seating depth. In the end, I had what promised to be a good load so I loaded up 100 rounds in two reloading sessions and went for some long range "testing." After a hundred rounds, I had a load that would was in the 1/2 minute range (pretty good for me), an average velocity of 3032, and SD of 7.4. Time will tell if over numerous loading sessions the numbers stick, but a 100 shot sample size over two sessions is certainly more than most guys do.

Based off my own empirical evidence (which is subject to change as further data is collected on the topic), you'll find that powder burn doesn't necessarily produce linear velocity increases, hence a "node." But good groups don't always reside in the flat spots (there goes the rest of the guys). I think there has to be a happy medium. Keep in mind that seating depth, brass prep, component performance in a given barrel and chamber, and other factors also produce their own affects, so the conversation probably needs to be a bit broader than just powder burn. But, FWIW, here ya go.

 

[Ledzep]

Based off my own empirical evidence (which is subject to change as further data is collected on the topic), you'll find that powder burn doesn't necessarily produce linear velocity increases, hence a "node." But good groups don't always reside in the flat spots (there goes the rest of the guys). I think there has to be a happy medium. Keep in mind that seating depth, brass prep, component performance in a given barrel and chamber, and other factors also produce their own affects, so the conversation probably needs to be a bit broader than just powder burn. But, FWIW, here ya go.

6mm ARC powder charge vs. velocity (each color a different powder). Yellow track had pressure issues at the top.

6.5 Creedmoor. The drop tail on the green line was testing a 2nd lot of the "same" powder.
This one is especially telling with the light blue track, 35x shots ea. every .3gr. The deviation you see from a linear trend line is so miniscule you will never see a difference on paper or steel within the effective range of the cartridge. It's effectively the "noise" level present with a 35 shot sample.

ETA: You will see "swoops", like that yellow ARC line, but I have not seen any reliable "sinusoidal" "node" data sets in .223, 6 arc, 6.5 creed, .308, nor .300 PRC.

 

[TriggerJerk!]

@Ledzep Homogeneity of slopes is interesting in your two graphs (note the axes are flipped). As different powders were used and produced similar slopes in these two tests, this provides emperical evidence for those following this and the “Flat spot myth” discussion.

A database of peer reloading data and outcome metrics might yield interesting results via principle components. Food for thought.

Regardless, great input. Thank you.

 

[Ledzep]

Yeah I've heard the rule of thumb of 5-7fps per .1gr or 50-70fps per grain thrown out several times over the years, which does tend to track fairly well with most of my results. I'm sure departing from typical bottleneck 50-65ksi rifle cartridges would/could change that. I wouldn't be surprised if a .45-70 was quite a bit different, for example. I have also seen slow-for-cartridge powders produce something like 30fps gain over 2 or 3 grains, which is really just an indication that you're doing it wrong , but that's as close as I've seen to "flat spots".