Hi Folks,
Perhaps we need some documentation here. From Neal and Back "The Mantons: Gunmakers" page 16:
"John Manton (not Joe) designed a breech which, instead of screwing into the barrel, screwed over it, ..... He took out a patent for this in 1797, and was still using it as late as 1808. Hawker refers to it on page 29 of his 2nd edition, adding that he had to relinquish it because it was proved unsafe. The fact remains that John Manton turned out a large number of guns with this form of breech over a period of 10 years. A cased single barrel in the collection with the serial number 4992 made in 1808 shows signs of much wear and use, and we have never observed one damaged or in dangerous condition. It did have one great advantage over the conventional form of breech, in that it was much easier to unscrew; so much so that it is possible that owners of these guns tended to unbreech them too often and by so doing wore the threads, which could cause weakness".
Neal and Back include some photos and also list several examples of these guns in their appendix.
dave