Gun-lock firing mechanism, endless screw and springs
A spring-and-lever lock that gives fire to a scoppietto, with an endless screw driven by a wheel
The upper half of the sheet shows a drum set between plates and driven by a wheel, described as an endless screw (vite sanza fine) in which the wheel c is the first motion and a small wheel makes the screw a turn in the same sense. The lower half is devoted to the lock of a scoppietto (a handgun): several assemblies with serpents, springs and levers give fire to the powder. Leonardo specifies that the lever f m is two and a half times its counter-lever m c, that the lever measures one seventh of a braccio, and that this seventh is the module for all parts of the instrument; the piece is cocked by drawing the serpent K back to L. A circular spring (molla circulare) is also drawn at the center.
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Lock that gives fire to the scoppietto
The office of this instrument is to give fire to the scoppietto (handgun) with the front g, while a part immediately uncovers the pan of powder so it ignites. The lock is cocked by pulling the serpent K back to L.
Endless screw driven by wheel c
In the upper instrument the wheel c is the first motion, and by a small wheel the screw a is made to turn in the same sense as c, forming an endless screw. The arm of the middle wheel leaves one screw, enters the other, and then returns.
Lever and counter-lever proportioned by a seventh of a braccio
The lever f m contains its counter-lever m c two and a half times over; the lever is one seventh of a braccio, and by this seventh all the members of the instrument are measured. The front c of the counter-lever, driven by the spring p h, pushes the heel n, which raises the spring v x.
Circular spring
A coiled circular spring (molla circulare) is drawn as an oval band at the center of the sheet, one of the spring elements powering the lock mechanisms below.