The shrink-on method, cannon frette in French, is not holding the barrels by hoop tension, it also uses solder. Darne barrels are held that way with obviously good results.

TennHillBilly, the most prolific barrel experimenter was Henri Pieper, he used a variety of barrel jointing methods in his shotguns: demibloc (with dovetailed barrels), monobloc with the barrels inserted from the breech ends, monobloc with the barrels inserted from the muzzle end, threaded monobloc and others. Other than Pieper I have not come across barrels threaded into the monobloc by a commercial maker. They must exist, I am sure, but the numbers must be small. From experience I learned that gunmakers hate threading parts. Even after a four hour argument a gunmaker refused to put a split bottom plate on a boxlock shotgun because it would take an extra threaded screw hole about 4 millimeters in diameter and 10 millimeters deep. The guy would be apoplectic if asked to thread two barrels and two chamber ends 70 millimetes each!