I know no way to "shrink" primer pockets .
A swager is used to swage crimps out of the way & to make tite pockets more uniform .
Actually there is. Not only does a swager remove the crimp, but the "cup shaped" end of the rod that enters the case swages the brass into and against the form the enters the primer pocket from below.
I read about this some years ago, doubted it, bought one, and have used it to tighten my Federal .308 Win. Match cases and my .22 Hornet cases (both Rem. and Win.) It works.