Yes, the G23 is my work carry sidearm, and some sites I work at require 38 or 9mm, and exclude the 40SW (and 45ACP). Simple fix is to change the barrel for around $100. It is like having 2 guns. I bought 9mm magazines, more for California 10 round rules.
You can read about Glock factory interchangeable barrels and upper receivers here: http://www.glockmeister.com/Tech_Info.asp
Lone Wolf makes custom conversions, ported barrels, etc.
LWD Barrel M/23&32 Conversion to 9mm Stock Length http://www.lonewolfdist.com/Detail.a...OD=983&CAT=238