Originally Posted by highrolls
So for an experiment to be viable, the tumbling would have to allow for the powder to move against itself within the case and that amount of movement would have to be quantifiable and repeatable. In addition, where grain size/shape is a factor in burn rate control, that would imply a separate experiment for each powder type.
Uh huh. And that's the difference between what a peer-reviewed scientific journal might require and what ordinary people will accept as common-sense, every day life. Of course, these scientists are the same people that won't accept that surgical sterilization works on deer unless the animals are tracked to prove that they don't have babies.
Powder that's traveling is being shaken against other powder and containers non-stop. There is zero reason to believe that there would be any difference between that and a vibratory tumbler. I've never seen any indication that the problem is some sort of resonance or fixed frequency. The claim is that the vibrations will "break" the powder or make the flakes smaller.
Repeated test with various powders have consistently shown that there is no effect. Rifle powder, handgun powder, many powders. Time frames up to over 200 hours. That's enough for me and most anybody who accepts a reasonable amount of every day experience to make decisions. If you require scientifically valid, controlled, blind studies, so be it. Don't tumble your ammo.
Still happily answering to the call-sign Peetza.
The problem, as you so eloquently put it, is choice.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.