Swaging brass tube

[Toolmaker51]

telescoping brass tubing googles easily but the .com vendors may not suit delivery in Queensland.
Biggest issue to swaging your own is a question of power, whether drawing through a die or building a rotary swage. First step is supply of annealed tubing, or annealing commercial half-hard lengths. Any sites dealing with reloading of rifle cartridges will cover the simple process; it is air cooled not chilled.
If I was faced with producing an airtight seal, first attempt might be felt 'o-rings' and lube used by brass musicians.