I have used multi choked guns in one form or another since the Winchester 101 and Beretta 301 auto days, that also included a Breda auto with Cutts and multi choke. I have NEVER had any issues with their use. The only minor problem was with Teague extended in my Beretta 303. They would back off a couple of turns after every 10 to 15 shots, even when tightened with the tapered key. I simply switched to Briley extended, problem over. My Browning DS chokes are virtually spotless when I remove them, after every 5 or 6 outings, having broken the initial seal with the key they unscrew by hand, so I see no need to try and clean the internal threads. I simply wipe the outside of the choke, coat with a red tacky American gun oil and refit, job done. The same applies to the Briley choke in my Beretta 303, although that does get a touch dirtier, it still unscrews by hand after breaking the initial seal with a tapered choke key. I then carry out the same routine and no problems. I have never had to clean the inside of the barrel or the internal thread, before refitting the choke but that maybe due to the oil that i use. I leave the choke in place when cleaning the barrel and only remove them after 5 or 6 outings.