The Norwegian Kongsberg factory has a history of making firearms-based tools for maritime use, and one of the more recent is the M52 line-throwing gun, introduced in the 1950s and sold through the 1970s. It uses a repurposed Mauser action paired with a new smoothbore barrel and a 12mm blank cartridge to fire a rescue line.

A couple of different projectile heads were made, including a floating wooden one, a smaller solid steel one, and rocket-assisted ones to increase the range from about 100 yards to nearly 300 yards.

Two versions of the same basic gun were made, one for throwing line (for maritime rescue, firefighting, and construction) and one as a harpoon gun for hunting whales. This example is line thrower, and particularly cool because it includes the complete original case and accessories.

Video: [8:38] https://youtu.be/fUoE0N6alV4?si=