One other observation/question. My chokes, including the Beretta factory chokes, shoot loose. Where does the torque come from? I’m not enough of a Machinist to know if this is a function of thread pitch,shape, depth, etc. Obviously it contributes to the dirt, because as it backs off it breaks whatever gas seal there is.
Your Beretta chokes shoot loose? You keep them clean and lubed. My chokes are generally slightly dirty and I don’t usually lube them. They don’t shoot loose. I believe that this is a small victory for Demon Sloth.
If you absolutely insist on properly cleaning your chokes and the barrel threads (as my mother used to insist that I clean my room), try degreasing the threads on the tubes and putting on a little bit of clear nail polish. Let it dry before you reinstall the choke in the gun, of course. The nail polish will give you just enough “grab” so that the choke tube probably won’t loosen up – even if it is cleaned and greased. I have done this with a Briley choke that has a sloppy fit in my Model 42 and it has worked perfectly. This technique has also worked very well for the bearing surface of skeet tubes which have loosened up. The nail polish lasts a surprisingly long time.
I don’t have the vaguest idea where the torque comes from that loosens the tube up. It may be just general banging around. When the tubes are screwed in, there is residual stress on the threads. The vibration of the shot passing through may enable them to ease that stress by unscrewing slightly. At least that theory sounds good.
On the other hand, loose screw chokes could give credence to the “wad spin” theory that the people selling straight rifled skeet tubes adhere to. For the life of me, I never could figure out why straight rifling was needed to stop wad spin because I couldn’t understand what got the wad to spin in the first place. The Bernoulli effect? The earth’s precession? Bad moon rising? I remain unconvinced that wads generate any noticeable spin in the bore- but I am always willing and anxious to be proven wrong. Maybe choke loosening is connected to wad spin in some way? Until someone makes the connection in a way that even I can understand, I put wad spin in the “hooey” file, along with perfectly even pattern distributions and 3-1/2″ autos that can reliably shoot ultra light loads.
The Technoid at <www.ShotgunReport.com>
(Often in error, never in doubt.)