Here is a discussion from this site from a few years ago where I'd shared a bit of my process for the pinfire guns and rifles.

http://doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=147110&page=all

Note the comment on base wads. When you mess with the head of a shotshell, you might be messing with the way the base wad is secured. Not all shotshell hulls are the same.