With a shrink fit there would be no distortion of the barrels as the monoblock is heated and the barrel is cooled in liquid nitrogen. This provides a very strong fit which if the machining finish on the mating components is good, ie. a ground finish and they are both parallel then there will be a strong bond. Often components joined in such a manner are impossible to press apart without deforming one or both components, and require machining to separate. Fine threads pose no problems, most clevis joints on hydraulic cylinders use very fine threads and look at the forces that they are dealing with. Gun making which dates back hundreds of years traditionally use solder as they did not have the materials to make decent cutting tools such as taps. Parts were soldered and keyed. Today's materials are infinitely better than even 80 years ago and not only are fine threads usable, they are desirable, providing of course on doesn't go ridiculously fine. Beretta even used a Loctite type adhesive at some stage to join barrels into the monoblock of its shotguns. Merkel proudly advertised for many years that their demi-block barrels were joined by soft solder, they were however also keyed behind the ejectors with two long Scotch keys.

Waidmannsheil.