I had a Gen4 29 and bought a KKM 4 port comp for it. It worked just fine, definitely got a velocity boost over the factory G29 barrel. I was getting around 100-150 fps more out of the KKM 4 port than I was the G29 factory barrel even though barrel wise there's only about .4" more barrel. I don't have it any longer, but I had no issues with it.