From Wikipedia >There are currently no known gun-type weapons in service: advanced nuclear weapon states tended to abandon the design in favor of the implosion

From Wikipedia >There are currently no known gun-type weapons in service: advanced nuclear weapon states tended to abandon the design in favor of the implosion-type weapons, boosted fission weapons, and thermonuclear weapons https://en.wikipedia.org/wiki/Gun-type_fission_weapon https://en.wikipedia.org/wiki/Gun-type_fission_weapon It seems like clearly the inferior method, the USSR never even bothered with them.