Pete;
Thanks for posting page two of the 1881 patent. As I have no reference to an earlier one I am taking this as his original patent. From both the illustrations & the description it is obvious this patent did not describe the bbls being threaded in. As to whether this patent was sufficient to protect against a gun being fitted with a one piece breechpiece with bbls joined by some other method in Blgium I do not know.
I do not believe it would have done so in the US. Note that D M Lefever was issued patent #205,193 on June 25, 1878 for a Doll's Head rib extension having a sq shoulder rather than the normal curved cone. Some time later Remington Arms began using a sq shouldered doll's Head on their doubles. Lefever sued for infringment & lost the case. The basis of his loss was that he had written the patent stating the mating surfaces of the Doll's Head & the recess in the breech were cut on the Arc of a Circle having the hinge as center. Remington won on the fact they had cut their shoulder on a straight line being tangent to the circle rather than a part of it. Lefever argued that the Sq Shoulders were the basis of the patent, not whether it was cut on a arc or straight, but Rem prevailed.
