Depends on what you mean by clean. Since rifle brass gets lubed before decapping/sizing, and then tumbled again (to remove the lube), the pockets might get cleaned a little...but I don't do any specific pocket cleaning. In fact, I'm considering removing the decapping pin from my rifle sizing dies (I have a universal decapper in my loading tool head) so I don't have to worry about the possibility of tumbling media getting stuck in the pockets. Anyone do that? If the primers are properly seated, they shouldn't interfere with trimming on a trimmer that trims based on brass OAL, should they?