Meaning of seven-bore in English:

seven-bore

adjective

(also 7-bore)
  • (Of a gun) having a bore of approx. 0.87 inches (22.2 mm), corresponding to the diameter of spherical lead bullets weighing one seventh of a pound.

noun

(also 7-bore)
  • A seven-bore gun.

Origin

Mid 19th century; earliest use found in Bell's Life in London and Sporting Chronicle.