With M16A1s in the Army in the 1970s, we drove out the pin, and then lightly gripped the tube with a set of parallel jaw pliers, and tapped on the pliers with a small hammer until the tube crept back out, and free.
The tube is not paper thin, and you won't crush it, unless you are a real gorilla. But if you work at it, you can screw it up.
Also, good idea to make sure the tube isn't carbon frozen in place. Not likely, but could happen. A good penetrating solvent and some time to work can remove this concern.
All else being equal (and it almost never is) bigger bullets tend to work better.