380mm the inner barrel, its a vfc avalon rapier the barrel is quite big. , a photo of what mate? sorry im a noob.
i did what you suggested about shining a light, i do see the light through the barrel constantly. when i look up the bb feeding tube, the nozzle from the lower receiver only covers the hole when i fire the RIF. (the nozzle cannot be seen through the feeding tube unless i fire for a split second )