Will a Gen 5 barrel work in a Gen 4 slide/frame?

Which gen5 to which gen4?

You can use the gen5 19 barrel in gen 2/3/4 19/26 and vice versa

You can use the gen5 17 barrel in a gen 2/3/4/5 19/26

You cannot use a gen 2/3/4 17 barrel in a gen5 anything.

The lug setup of the gen5 17 is the same as the Glock 19.

So pretend the gen5 17 is like a stretched 19.

Thanks Chowser, just dropped a KKM barrel into my G-19 Gen 4.