I have heard that a certain book by the designation of "TM 31-210" is very interesting. Also a weapon I heard about called the "four-winds shotgun".
where do you get the ammunition from do you have to make it
If you can't buy ammo, then yes. Don't wanna give too much detail cuz illegal to provide such information in my jurisdiction, but most guns use blanks that they modify with projectiles, though there's been talk of various means to re-activate inert ammunition, I know Deterrence Dispensed put out a guide called "ButWhatAbout Ammo" discussing this. Two methods were discussed in a book "Stingray Machine Pistol" too.
(Legal ass-covering disclaimer: I have not provided any genuine instructions beyond vague descriptions that hardly could be considered such, and while I have provided names of publications that may be instructional, I will not provide links and am mentioning them for journalistic/scientific reasons, giving your sources is important. I am providing information to people who I believe are interested in this subject out of curiosity, and I believe live in jurisdictions where making such things would be legal anyway. Obey the law, worship the state, do not question the party)
(photos are not mine, taken from Improguns)