I didn't make tests myself, but as i 'm interested in pneumatics, i read the tests that Cedric (MIZALO) did. I think you can still read it on the "Spearboy" french forum.
Unfortunately, the French preparers of pneumatics are not very talkative. You can find some videos of SS barrel pneumatics (carbozzi) on youtube. Or you can directly talk to the first Carbozzi creator: Romain Orazzi ( the new one is CHristophe Cattini).
For the Duccio works, i find his Facebook page very interisting: you can check your self at
"Elaborazioni oleopneumatiche AIR GUN'S TECHNOLOGY" ! He makes a lot of ppenumatics products . as an an exemple you can see a muzzle which really looks like the new STC 3.0 muzzles, or inner barrels in aluminium, or other things... Some products ar to my mind very good, other are not!
THe italians are very found of pneumatics so it is interesting to see what they create.