The Independence by FX has a smooth twist in .22. they work well in .22 and .25 caliber, however they do not perform in .177
As Vinny has said, the tech is now licensed to FX and is not available as a retrofit for any other rifles, although Daystate did have a few for testing.
Somehow I made TEAM ENGLAND 2012 and 2013
Illiterate writer for AirGunner
The real Kung Foo Panda.