This seized .22lr improvised hand was made by modifying a staple gun, like you would use for upholstery, with a bent piece of sheet metal. The common but unofficial explanation I found for this was it was made in a prison.
I recall a movie where some kids were menacing another kid with a bullet braced in a vice while they were waving a hammer over a nail placed opposite the business end of the cartridge. Life, uh, finds a way?
NGL, that's brilliant. Very little modification needed to simply set off and crudely direct a rimfire cartridge.
I did a couple of year stunt as an IT Director at a sheriff's office and detention center. I was amazed at what ingenuity a bored mind and plenty of time can yield.
I was going to ask if this had a chance of working. Reading the article you posted convinced me that, whether this one actually worked or not, it is certainly possible to make a working firearm from a stapler and some scrap metal. That's pretty neat, a little scary, and leaves me wondering why more people don't do this. Why aren't there gangs using these?
For something like the pictured gun you're probably not getting much more in the way of accurate range than just holding a knife, and a knife would be a lot more reliable.
I would also assume that if you can get hold of ammunition to load an improvised gun it's not that much more of a stretch to acquire an actual gun to put said ammo into.