I didn't see any mention of the 870.The military is still using (the 870) too, have been since the last days of Vietnam
The most common type of shotgun used for this purpose is the manually-operated, slide-action/pump-action type, because it is commonly believed to be less prone to malfunction (particularly when dirty) than semi-automatic designs. Pump-action shotguns are also less expensive than their semi-automatic counterparts. Even so, semi-automatic shotguns such as the SPAS-12 and Benelli M1014 are currently seeing service in NATO-aligned armed forces. The Mossberg 590A1 is currently the pump-action of choice for US armed forces and has seen service with other militaries.