I don't konw that I would call reforming brass to the proper chamber dimensions so it can be used in vintage firearms or swaging bullets to fit the bore "cobbling" or a "Bubba Fix". Especially since by your own admission you don't know enough to do it right. Pray tell, what is the difference between reforming a parent case and bullet to fit a firearm or modifying the firearm to fit an ammunition? I would do the former much before the latter.
Reforming brass was never part of the original question. We were speaking of bullets.
Swaging from what I can tell involves squeezing a bullet to a slightly smaller non-design spec diameter by running it through a single or series of dies. While this squeezing of the bullet may be akin some of the processes used to make the bullet originally it is not a process that someone sitting on a bench in a garage somewhere can reasonably expect to have any meaningful control over from a quality control standpoint. Yes, you can make it fit. Is it the same internally as you pulled it out of the box? No. Are you going to waste otherwise useable bullets from your tinkering? Most likely.
If you are comfortable doing this sort of tinkering go for it. I am not. Things that go boom are designed to specific tolerances for a reason.
The aim of my original question was to determine the feasibility of altering a firearm purchased at a reasonable price to fire current standard munitions. I have no interest in messing around with obsolete cartridges or paying out the nose for antique cartridges from some boutique manufacturer. If that is your interest... more power to you.
As for repeating all of this "Bubba Fixing" every time a bullet or a case is prepared... every step you add to production introduces a chance of failure, a chance to introduce uncertainty to the end product. I like my hands, arms and face in their current configuration. Loading a bullet that could cause a catastrophic over-pressure event is something I would rather avoid.