Can magazines for the Glock 22 be converted to 9mm?  What's required, a 9mm follower?

My first thought would be that the magazine lips might be spread too far for a 9mm to feed properly.  I'm not sure that it would hurt to insert a G17 follower and try it though.  Provided that I didn't have to start trying to alter the mag lips.  Sounds like an interesting experiment.

          WAIT a Second..........

Nope!  I just tried loading a G23 mag with 9mm rounds.  The lips are too wide to support the 9mm cartridge.  The rear of the case is secure, but the front is not supported sufficiently.  You might could screw with it and make it work, but I wouldn't be willing to sacrafice a .40 mag to do it.  It would also make any postban mags that you have illegal, since the mag capacity would exceed ten in 9mm(Maybe not, but I wouldn't want to test the waters).

geesh...you have a $400+ gun and you want to play footsies with the magazines??? The .40 S&W magazines run around $22. Why compromise your life or gun for that??

Quoted: geesh...you have a $400+ gun and you want to play footsies with the magazines??? The .40 S&W magazines run around $22. Why compromise your life or gun for that??

That's why I was asking the question and not "playing footsies with the magazines".  If it was perfectly ok to do, then there wouldn't be a problem now would there?