Just recently picked up a gen2 glock 19 . I also own a gen 4 G19 that has been sent back to glock twice for ejection issues. I attempted to put barrel from the Gen 2 19 into the gen 4 and it would not fit. But .. the gen 4 barrel fit into the gen 2 slide just fine. I found this to be a little odd thinking that the barrels are supposed to be interchangeable. Has anyone heard of this before?