Hop up at the other end?

Choking the barrel may not work with airsoft. I know many target rifles, both air rifles and powder burning rifles, have barrels that use choked barrels. And yes they work great! BUT they will actually squeeze the round into the rifling more than at the breach of the barrel.

So I can't really see it working for an airsoft barrel. Though you wouldn't have to sqeeze the bb all that much, just as long as you can get it to exit the barrel the EXACT same place everytime then you would be golden like a shower.

It may be something to look into, but I am going to remain kind of "iffy" about the inner barrels. But hey, prove me wrong and I will eat my words And I will offer to test them as well, that is if anyone can make some.

Making them........ Beck, to make a few have you a mandrel on your lathe? I know a knurler is similar, atleast if I am thinking correct. You would be able to match the outter barrel, and while spinning the inner barrel, as fast as you can, slowly close the mandrel. Thus squeezing the inner barrel to the diameter that you need, and making it longer by nature. I would say go for like a 6.00 barrel at the end and see what happens.

I have been looking in that, however for most of us here in the US it would be illegal. As soon as you rifle the barrel it is considered a real firearm. That in itself is not the issue, the issue would be that since it would be a real firearm under the NFA, it would have to be sized as such over all. Its not illegal to make your own firearm... yet. However once there is rifling, if there is a stock, the barrel must be 16" and the OAL must be 26"... all that in addition to your local laws.

For the time being I think it would be better to focus on barrel issues/modification and custom BBs... IMO... as much as I would love to see rifled barrels, there are just too many legal issues these days in regard to having fun