SD, ES, and temp stability

[Greyfox]

I

so you are saying that powder/burn rate has absolutely nothing to do with sd and es?--I don't totally agree with that

I know that "exact" powder charge, neck tension, annealing, etc all play a major roll in sd and es spread --but I gotta believe that the powder itself also plays a roll in it too.

I have seen lower ES and SD in my 30-06 with RE16 than any of the other powders I have tried in that cartridge/rifle-- my reloading technique/process and brass did not change at all regardless of what powder I used (same bullet for all powders tested) ---that leads me to believe that some powders will have a smaller spread than others due to the powder itself

I was trying to see if anyone had actual recorded data on a test like this to see what others have come up with

You are correct that powder selection and weighing accuracy can certainly come into play with SD/ES, but unlike a powders temperature stability which tends to be independent of the cartridge/rifle, SD/ES is influenced by a multitude of variables controlled by the individual as well as the barrel/chambering characteristics. Another shooter with a load similar to yours may very well achieve a better or equivalent SD/ES with a different powder with his barrel and methods. I have personally been able to achieve low SD's(<5) with Varget, H4350, and R-16(amongst other powders)by optimizing my parameters. I would agree that some powders achieve SD more easily then others, but IMO it would be difficult to build a reference chart. Chemical properties like temperature stability and burn rate, on the other hand, are measurable determinants of the powder alone, enabling the use of fairly reliable reference charts.

 

[Wachsmann]

SD/ES is largely a function of the particular load, components, and barrel. Temperature stability is a function of the specific powders chemical composition. This chart that was posted a couple of years ago. It doesn't include the recent Alliant introductions. The results shown in the chart for H4350 and Varget are very close to my own experiences.
View attachment 135856

So If I'm reading the chart right it looks like H4831SC is the most temp stable powder on the chart. This may have explained the consistent data I got out of my wife's 243 a few years back. I still want a little more speed out of it but I through the load together a few weeks before season and it was shooting in the .3's and SD and ES was under 10. But like every one has pointed out there is a lot more factors involved. It just happen to work out that way for the bullet, case, powder and gun. I also seen very good results from 4350 and Varget. Looks like varget may had produce the most speed for me but the group and SD was not the most consistent. 4350 probably with a little more refining will be spot on for velocity and group.

 

[nicholasjohn]

so you are saying that powder/burn rate has absolutely nothing to do with sd and es?--I don't totally agree with that

I know that "exact" powder charge, neck tension, annealing, etc all play a major roll in sd and es spread --but I gotta believe that the powder itself also plays a roll in it too.

I have seen lower ES and SD in my 30-06 with RE16 than any of the other powders I have tried in that cartridge/rifle-- my reloading technique/process and brass did not change at all regardless of what powder I used (same bullet for all powders tested) ---that leads me to believe that some powders will have a smaller spread than others due to the powder itself

I was trying to see if anyone had actual recorded data on a test like this to see what others have come up with

I think you'll find that what delivers the best SD & ES in one rifle/cartridge combination may or may not be the best in that regard in another. There are so many variables in the equation that each one is different. If you bought two consecutively numbered production rifles, in the same chambering, barrel length, etc., you could developed a load for one that was absolutely perfect, and it wouldn't surprise me one bit if it didn't perform worth a **** in the other.

I think it's best to look at the things that are known to contribute to delivering good SD & ES and make that your starting point. If there's a shortcut to finding the best formula, I'd sure like to know about it. I don't think there is a way to know for sure. I do know that I have had best results with a powder that most nearly fills the case.

As far as the temperature sensitivity issue goes, most of the guys on this forum ( and others ) seem to be finding that the Hodgdon Extreme line of powders takes the trophy in that arena. I have found this to be true, as well. The table somebody posted here in answer to your question bears this out. I noticed that the old H-4831 showed more temperature sensitivity than the H-4831SC. It must be that the old version doesn't employ the same technology as the short-cut version.

 

[Tree Farmer]

Let me ask this. If you had similar accuracy between loads of RL16 and H4350 at 50 deg. F, would the sd & es change for the same load at 80 deg. F, and all other things equal, which powder would show the larger spread?

 

[nicholasjohn]

Let me ask this. If you had similar accuracy between loads of RL16 and H4350 at 50 deg. F, would the sd & es change for the same load at 80 deg. F, and all other things equal, which powder would show the larger spread?

I sure don't know the answer to that one. Hopefully somebody who knows a lot more about this than I do will field this question. I also don't know if the temperature sensitivity issue would show up with straight-line variation as temperature changes. I kinda doubt it, because powders behave differently at different pressure levels. So, it may be that as one approaches ( or exceeds ) maximum pressures for his particular rifle, things would get more erratic in all respects.

 

[Point_Taken]

Bump for a good subject