wheel lock

  1. an early type of gunlock in which a rough wheel is spun on a piece of pyrite or flint to throw sparks into the pan and set off the charge
  2. a gun with such a lock

See wheel lock in American Heritage Dictionary 4

noun
  1. A firing mechanism in certain obsolete small arms, in which a small wheel produces sparks by revolving against a flint.
  2. A firearm using such a mechanism.
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