Found this on another site
Glock Barrel Compatibility
It is asked often and many folks get the wrong information, so we are going to show the Glock owner and the generally curious all of the possible Barrel/Gun combinations in the Glock. In other words which barrels work in which guns.
Barrel ------------Gun/s
G17.....................G17
G17L...................G17,17L,34
G19.....................G19,26
G20.....................G20
G21.....................G21
G22.....................G22,31
G23.....................G23,27,32,33
G24.....................G22,24,31,35
G26.....................G26
G27.....................G27,G33
G29.....................G29
G30.....................G30
G31.....................G22,31
G32.....................G23,27,32,33
G33.....................G27,33
G34.....................G17,34
G35.....................G22,31,35
Glock Upper Swaps by Model
It is asked often and many folks get the wrong information, so we are going to show the Glock owner and the generally curious all of the possible Upper/Receiver combinations in the Glock. In other words which uppers work on which receivers.
* Indicates ejector and mag change.
Receiver------------Upper/s
G17.....................G17,17L,34
G17L...................G17,17L,34
G19.....................G19
G20.....................G20,G21
G21.....................G20,21
G22.....................G17*,17L*,22,24,31,34*,35
G23.....................G19*,23,32
G24.....................G17*,17L*,22,24,31,34*,35
G26.....................G26,27*,33*
G27.....................G26*,27,33
G29.....................G29,30*
G30.....................G29*,G30
G31.....................G17*,17L*,22,24,31,34*,35
G32.....................G19*,23,32
G33.....................G26*,27,33
G34.....................G17,17L,34
G35.....................G17*,17L*,22,24,31,34*,35