The wire melting is just a game mechanic to stop the player from continuing his dogfight.
The wires go from the stick to the cockpit, perhaps to a fuse, to a main bus, to a battery, whatever, then eventually out to the guns.
Anywhere along the way, all you need is the paper insullation (I believe that was used at the time) to burn off and the wires to touch, shorting the system and negating trigger presses.
That could happen anywhere in the wings or fuselage, and it keeps players from dogfighting til their wing pops off.