I would not shoot that gun if .018 is the correct wall thickness. Have it remeasured. If it is thin to that much I would contact the seller and see if they will take it back. You asked for minor work to be included int he sale and it sounds like it was a major job that they did. They should have measured it then and informed you of the true condition of the gun. There are too many good guns to shoot one that thin. Even of you are right handed your left hand is your second most favorite hand and counting to ten is not to be lost as a skill due to a minor barrel failure.