Gentlemen,
Bruce F. gave some good advice about cutting down barrels, but I find that the process is greatly improved by using a standard pipe cutter, not a tubing cutter. Most tubing cutters will fail if put to the task of cutting steel. A pipe cutter is a tool used to cut primarily black steel pipe. It is very similar in design to the tubing cutter but substantially more robust and up to the task. – Tim in CT