...
Another problem with using the brass tumbler and most brass polishing agents is that many of them contain harsh chemicals that weaken the brass each time you clean them thus shortening the case life.
...

Avant je laissais aussi mes douilles 2-3 heures dans le tumbler;
Mais depuis que j'ai changé pour le média vert de Lyman, 1/2 heures et tout est clean.

Quel sorte de média utilises-tu?

....
Rifle Brass
Our rifle brass is processed the same way as our handgun brass and the benefits to our method of cleaning the cases using our system is obvious. First, neck tension due to the completely clean inside of the neck helps increase accuracy and extends case life. The magnetic pulse function of the process serves to realign the molecules somewhat like cryogenics in freezing metal and make the case return to its natural state and won't let it get hardened.
...

...
POLISHING BRASS.... Smooth and uniform case mouths are very important in producing accurate reloads. Therefore, I don't polish my carefully prepared brass in a tumbler. During polishing, the case mouths are hammered against the other cases in the tumbler. The hammering rolls over a small lip or burr on the ID and OD of each case mouth. This peening process also locally work hardens the brass. These tiny rolled-over rings of brass at the case mouths are harder than the rest of the annealed neck. These rings and tiny peen marks are very obvious on new brass. If you look at your nice shiny cleaned cases out of the tumbler, you will see the battered case mouths!
...