Well fitted and with the necessary bite they are effective . But like all mechanical devices they need to be kept in good order and if the rest of the joint comes slack then so does the dolls head [club head , spade head ] . Problem is that on 100 year old guns that have not been well maintained or been to the local black smith ,no slur on blacksmiths here , then no it will not be much good . Point of fact I have rarely seen a cross bolted gun in which the cross bolt actualy serves a useful function and many from which they have been removed .