ORIGINAL: Bernie P.
It's not necessary to tumble case's.The cleaning media can "burn" to the inside of the case over repeated cleanings which changes the case's capacity resulting in different pressures.You do need to clean off the sizing lube and the powder residue from inside the neck area and primer pocket but that's all that's needed.
I understand where you are coming from with this, Bernie. I do, however feel for tumbler media to cause the fps spread Brush hunter claims to see, it would almost have to be the same amount of media each time in each casing. I personally don't think you could possibly get that lucky
.... or unlucky
... Something very uniform and constant would have to be happening..... Just the way I see it...