I have heard some things about putting 9mm barrels in a 22 without having to switch anything but the barrel and the mag, and maybe extractor.  Has anyone heard this, or tried it?
I posted on the glock forum but it doesn't seem to get much traffic.  Thanks for the help fellas

Brad

Yes. You may be able to do a switch with just the barrel. Your reliability may vary. If you switch extractors, and mags also you will have pretty decent reliability.

The breech face is milled for 40s&w....not 9mm..you need a COMPLETE topend AND 9mm ejector block.

Specifically regarding the .40 to 9mm conversions in Glocks. The different breech faces are not a concern. Many people make this conversion with no problem. I've seen many of these conversions for pistol competition where the guns are fun hard and fast with no problems.

Sure....why don't you just trade out a.45 barrel for a fourty...It'll work...right??    

No there are only specific combinations for barrel conversions.

If you have a glock .40 you can convert to .357 sig or 9mm with no problem. I've seen them, I've shot them. There is plenty of people on Glocktalk that will vouch for the conversion.

The Glock 21 can be converted to 400 corbon, and .40 super. The Glock 20 can be converted to .357 sig, and .40. I have not seen or shot any of the Glock 21 conversions. A guy at our IPSc matches shoots a Glock 20 (10mm)to .40 conversion.