Do any military or special forces shotguns have rifling?

Answer 1

No. The military uses shotguns for short range anti-personnel in urban combat and door breaching.

Civilian hunters use rifled shotguns to hunt larger game, primarily deer, at medium distance of 50-100 meters. They fire solid projectiles called slugs and jacketed slugs called sabots. When firing a solid round, a rifled barrel is more accurate than a smooth bore. When firing traditional shotgun ammunition of buckshot and birdshot, rifling offers no advantage.

Hunters use a rifled shotgun in areas where rifles are prohibited due to risk of accidentally penetrating houses, and because it offers the flexibility of firing birdshot through the same weapon. Since the military does not have those requirements, it uses a rifle, primarily M-16, for medium distance because the same weapon can be used for long distance.