A zero-stop mechanism comprises first and second stop members and a movement limit member. The second stop member is releasably secured to an adjustment mechanism. The movement limit member extends around a turret assembly and has a substantially annular main body from which a lug extends. In a first rotational direction of the adjustment mechanism, the second stop member comes into contact with a first side of the lug whereby the main body is rotated in the first rotational direction until a second side of the lug comes into contact with the first stop member. In a second rotational direction of the adjustment mechanism, the second stop member comes into contact with the lug second side whereby the main body is rotated in the second rotational direction until the lug first side contacts the first stop member.