The majority of european medieval crossbow ‘s in later middle ages used a long trigger “lever”, running directly on the roller nut. The lock trigger was fitted into a metal notch (sear) in the bottom of the nut to protect the nut form being grind away by the lever.
The trigger was assisted in locking into the sear with a leaf spring or round spring.
Later, between 1450 and 1500 a more complex 2-axle lock appeared. It allowed a crispier and easier trigger pull resulting a more accurate shot. The 2 axle lock disadvantages were an increase in the loading speed.
By the 16th century in central Europe the clap-lock and the multi axle lock took over the 2-axle lock.Clap locks where much cheaper than the multi-axle lock and was used on medium power crossbows.
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