Comparison of the three types of gun fitted to the various Supermarine Spitfire marks (top to bottom):
Colt-Browning .303 machine gun (note barrel shroud, completely different to original US .30 calibre model)
Browning M2 .50 calibre machine gun
Two 20mm Hispano-Suiza HS Type 404 cannons
(both late 12"/305mm shorter barrelled Mk.V versions, fitted as standard only to the F.24 Spitfire, and both complete with the post 1941 Molins belt feed mechanism (BFM) fitted to Mk.Vc Spitfires onwards that allowed 120 round disintegrating link ammunition belts to be used replacing the earlier 60 round drum feed fitted to Mk.Ib, IIb and Vb Spitfires).