The Czech barrel is only about 14.7 mm so you have to get it sleeved up to fit the 16mm breach. The Bsa comes at 16 mm so a simple machine job to get it to fit.
You could ask Jon Harris or Mick Trowmen to machine it for you both are excellent engineers.
You could also take a look at chambers Walther barrels , Dave Killen bought one and was very pleased with the results. The new Bsa barrel has a rifled sleeve fitted inside an outer sleeve , not a good choice for the machining needed on a Steyr .