During WW2, a very cheap gun, single-shot .45 caliber pistol was distributed to partisans fighting in France.
https://www.youtube.com/watch?v=HgOfbG3mi_0
From the video, you can see it was a rather clumsy sort of weapon, but any fairly competent machinist or metal worker could build a similar one. Deadly close in, and a perfect example of the kind of “ghost gun” that would proliferate when the commercial availability of properly made handguns is made highly constricted.
Those FP-45 liberators were never dropped