i have a ps90, and my dad has a 5.7 (pistol). he is an avid reloader. he got a set of the rcbs dies when they first came out, and had no luck at all reloading them. he recently got a set of lee dies that have worked much better. lee doesn't catalog them, but if you call them direct, they will make you a set. i know lee sometimes has a little bad publicity, but i have never had a problem with any of their stuff, and in this case their dies are better than the others.
another thing to know is that brass that has been fired in a rifle seems to resize better than brass that has been fired in the handgun. the action evidently opens up a little quicker in the handgun, and a lot of times the neck is pushed WAY forward. i guess there is a little more dwell-time in the rifles, and they are easier on the brass. that being said, the brass is always HARD to resize. unbelievably hard for such a tiny case. our experience has been that the brass is only useable for a very few loadings, sometimes only one or two times.
i am definitely not an expert on the subject, but i have fooled with them a bit, and i have done some prior research on reloading the little guy. good luck with them!