If the inner barrel is too stiff that maybe the problem.
Inner barrel needs to be loose inside the outer barrel. If it is too tight it wont' seat very well and will cause jams, misfeeds, huge drops in FPS and other issues. Not good because this can end up breaking the nozzle if it jams up pretty bad.
Actually the whole hop up needs to be nice and loose inside the outer barrel. Usually it is the hop up that is tight and not the barrel. If this is the case just work the hop up into the barrel until it loosens up enough.
There are other reasons why the BB ends up rolling out. Make sure you have at least a bit of hop. If it is not that make sure the screws holding the hop up is tight and not loose. You can check to see if the hop up is fine by shooting the gun stocked and Chrono it. If its shooting consistently then the hop up is screwed on tight and has enough hop on it.
Other than that I don't know what else to recommend based off the information you've provided.
Biggest recommendation is just run the gun stocked lol :P
Of course I know how it feels to want to bling up your gun so yhaa hope it works out for you
