The set includes turned brass barrels
British QF 6-pdr was widely used in many tanks and other AFV:
Crusader Mk.III, Valentine Mk.VIII/IX, Churchill Mk.III/IV,
early version of Centaur and Crusader
AEC Armoured Car Mk.II
It is very simple to use in Your model, and makes it extremely realistic. Simply replace original plastic barrels.
Insert the metal barrel using Cyanoacrylate adhesives.