From the Wiki:
"A rook rifle is an English single-shot dropping block or break-action small calibre rifle for shooting rooks and rabbits, developed in 1883 by the gun-makers Holland & Holland. The original rifle was .295 bore, with an 80 grain bullet, but slightly larger bores of .300 and .320 were also made at the time.[1][2]
Because such shy game would scatter immediately after a shot, there was no disadvantage to a single-shot action. Rook rifles remained single-shot, rather than magazine loaded, until they disappeared after World War II."
Someone at IMA knows about as much as I do.
