Most plastic-framed 9mm pistols (i.e. Glock, HK, S&W, Walther) are in the 25-30 oz range. I'm sure you can find something even lighter (i.e. a mini-Glock with an extended barrel) but I don't see any practical reason for going under 25 oz unless you need one for concealed carry, which is not an option for most of us.