As long as the receiver and monobloc were precision machined by the "makers", it would make little difference if the barrel maker left a quarter of an inch of the breech of the tube protruding from the monobloc when the monobloc was shipped back to the U.S. The "makers" would just trim it off when fitting the monobloc to the pertinent receiver. Personally, I don't know whether tubes in normal monoblocs go all the way to the breech or fit on steps. It would seem like fitting them on steps would be a nightmare that would require messy adjustments. If I were to design them, they would go all the way to the breech to be trimmed. We can ask the Brits, we can ask Kirk Merrington, or we can ask Rich Cole about the Beretta procedure. We may get three different answers, but we will know more than before we asked.