Well, crimping a stainless steel tube actually isn't very easy, as I had to learn. So a solder free solution isn't really in sight.
Furthermore I do not like the gap between the screws caused by the crimping, as it hinders the flow of molten plastics. Therefore I came up with a solution, where the barrel is soldered to the upper screw.
So I've begun to make the barrel.
Next step will be the nozzle.