My instructions from my Clymer screw in choke tubes gives a minimum of .010 wall thickness over the .814 diameter of the 12 gauge choke tap. I never did one that thin as I felt they were dangerous. I've not done one of those in over 20 years due to the introduction of steel shot. The end of the barrel would leave with the wad. Steel shot was a game changer. I made my own choke tubes for my Browning BPS 10 ga that I got when they first came out. Faster and bigger was the only answer for steel shot and water fowl. I also made a scope mount for the BPS 10 ga and mounted a pistol scope on it for turkeys. It works well.
