Originally Posted by billiardcue
40 cal & .357 Glocks can be converted to 9mm.
Can it be done the other way? G17 9mm to shoot .357?
But even if you can, you really don't want to.
It's usually better to just get a second gun.
Notes from JR before he disappeared on African Safari.
"The frames of the 26/27/33/39 are all the same.
You can convert a 26 to a 27 by installing a complete top end and switching the trigger housing from 9 to 40. You will also need a 27 magazine."