It would be just as easy, and result in a more durable magazine, to make a die to stamp thin steel plate. Magazines are easily made with basic machine shop tools - simple forming and a couple of rivets and presto.... Sourcing the springs would be an easy endeavor.
I would imagine that you would need at least a two stage die for the stamping of magazines. You would also need a cutting stamp. So there would be the need for three dies. It is the making of the dies that would be complex. I would not want to go with rivets - but spot welding would work.
Just thinking out loud