When R.J. Mitchell and Joseph Smith were designing the Spitfire at the Supermarine company in the late 1930s, they wanted the Spitfire to have one quality in abundance: speed.

To help achieve that, they made the Spitfire as streamlined as possible. Those smooth lines that make the Spitfire so breathtakingly beautiful weren't put there for looks. By making the Spitfire "clean," the Mitchell and Smith made sure there wasn't anything sticking out into the airstream to cause drag that would slow down the aircraft.

To help you visualize this, imagine what happens when you stick your finger out the window of a speed car. You finger is small, you there isn't much air resistance and there isn't much drag. Now stick your hand out the window. That's a bigger surface so there's more drag, you can feel the air "pushing" your hand back.

So, they put the eight Browning .303 machine guns inside the wings of the earliest Spitfires. The guns fired through eight small ports at the front of the wing. This cut-away view shows you how they fit eight guns, each with 300 rounds of .303 ammunition inside each wing. The early variants of the Hawker Hurricane had a similar arrangement with eight .303 Brownings.

To further reduce drag, Spitfires (and Hawker Hurricanes) had red gun port covers fitted over their gun ports. Yes, the tiny irregular surface of the gun port and the gun was enough to slow down the Spitfire just a little bit! With the gunport covers, the leading edge was smoother. The gun port covers were thin, so all the pilot had to do was pull the trigger and the bullets would blow right through the cover.

Later variants, like this Spitfire IX, had two Hispano-Suiza 20mm cannons with barrels that stuck out of the wing and four .303 Brownings inside the wings.

This three-page guide explains the different wing types and gun arrangements used by Spitfires before, during, and after WWII.

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