46 CFR 160.031-2 - Type and size.
(a) The shoulder gun type line-throwing appliance shall be breech-loading for the cartridge and muzzle-loading for the projectile, of not more than 13 mm (0.50 in.) caliber, chambered for blank rifle cartridges, smooth bored, and properly stocked, with shot line canister attached in a position below the barrel.
Title 46 published on 2014-10-01
no entries appear in the Federal Register after this date.