These barrels are not compatible with G17.4 and G34.4OK, I thought the Gen 5 barrels were slightly different and would not work in previous Glocks, or perhaps I have it the other way around. That may be it.
At any rate, glad to hear you CAN use barrels interchangeably like this.
Barrel compatibility is between G26.4 and G19.4 (a G26 with a G17 barrel, ain't that cool? :dancing
The new gen5 changes that and makes G19 and G17 compatible.