Hi Guys,
Did some checking on the schematics. The DRS uses the same barrel tubes, STX liners, o-rings (or CF Sleeve) and liner lock nut as the Panthera/Dynamic/King/ Impact. You would need a new liner, CF sleeve, and Liner lock nut for your specific caliber and length. The only barrel parts that are DRS specific are the barrel inlet (caliber specific) and the Shroud (called Tube xxx mm DRS) which are length specific.
Bagnal and Kirkwood have the barrel inlets and Europe Airguns has the tubes. So, FX isn't providing a kit, but you can certainly build one.
Cheers,
Greg