What type of operating system do the Remington 1187 and 870 shotguns feature?

The Remington 1187 and 870 shotguns utilize a gas-operated system. This design features a mechanism where some of the gas from the fired cartridge is diverted through a port in the barrel, which then cycles the action to eject the spent shell and load a new one. This allows for smoother operation and reduces felt recoil since the energy from the gas helps in cycling the shotgun.

The gas-operated system is particularly effective for shotguns, as it can reliably handle different loads, including both light target loads and heavier field loads. This versatility makes these shotguns popular choices among hunters and sport shooters alike.

The other operating systems, such as recoil-operated and inertia-operated, do exist in various firearms but are not the mechanism used in the Remington 1187 and 870. Manual action firearms would require the operator to physically cycle each round, which is not the case for these semi-automatic and pump-action shotguns, respectively.