For the sake of objective discussion, I propose that there is no such thing as a "stable" powder and I don't think I'll get any debate on that... unless maybe you think a 7RM can out pound a 300 WM
. I think we can safely assume that some powders are more stable than others. If there was a powder or powders that were completely stable, I would certainly give them the highest priority in selection.
So, understanding that any and all powders will have deviations in performance with temp changes, we should know that there should also be adjustments in our ballistic solutions based on those deviations. The adjustments might be smaller or greater but they still need to made for long range precision and accuracy.
Some other considerations in the big picture are
Load Density - the closer to 100% capacity, the better for more consistent performance
Load ES - the reason should be obvious
Load/Rifle Precision, meaning which powder does the rifle like best? - see the above
The assumption, although not proven, is that Retumbo is "more stable" than RL33. I would agree that it's probably a good assumption. Based on the above, my question is.... so what?
Being a slower powder, RL33 will increase load density. It will also increase velocity. I find those two benefits appealing.
Whether or not it gives a good ES and/or likes the rifle will vary from rifle to rifle and other variables like brass, primers, reloading techniques, etc.
If it gives me good load density and velocity, I'm not going to write it off because it might be a little more unstable than Retumbo. I'll do my part to make it work and make the adjustments when needed.
338 Allen Xpress, RL33 load development