The set includes turned brass barrels.
It is very simple to use in Your model, and makes it extremely realistic. Simply cut off the original plastic barrel and drill a hole in the remaining plastic parts and insert the metal barrel using Cyanoacrylate adhesives.
Other versions of Firefly's cannons You'll find in our sets:
AM-48-095 - Fairey Firefly - Hispano 20mm cannons with uncovered barrels
AM-48-097 - Fairey Firefly - Hispano 20mm cannons in short fairings