If the mag tube is beat up, as this one was, you can use the swage to push through the tube and work the dents out as you go. This photo shows how beat up the bottom of the mag tube was.
Swage up on the vise for some serious nudging. It helps if you have hammer experince tapping out dents
reassembly starts with pressing the mag button back into the mag follower.
I now do this with a dowel rod chucked up in the drill press and the mag in the block.
Be very careful if you use a vise as shown and note that I have the swage supporting the mag tube during the push