The Department of Justice has issued a press release showing, over five years, from January 1 of 2017 to December 31 of 2021, the number of firearms sold by unlicensed dealers in the USA was less than 1 of 10,000 sold in the National Instant background Check System (NICS).
During the five year period, the number of firearms sold through the NICS system was; 14 million in 2017, 13.5 million in 2018, 13.6 million in 2019, 21.1 million in 2020, and 18.5 million in 2021, for a total of 80.7 million over the five years. (according to the National Shooting Sports adjusted calculations)
The number of firearms sold by unlicensed dealers during the five year period was 68,388 firearms. They were uncovered in 3,403 cases. 68,388 may sound like a great deal, but it is less than 1 firearm for every 10,000 legally sold through the NICS system, or .084%. The Justice Department prefers to use the term "trafficked". It may be more correct, because some of the firearms may be traded or gifted rather than sold. Of the 68,388 firearms "trafficked" by unlicensed dealers, there were 368 cases where the firearms were used in shootings. There were 265 cases where they were used in homicides. This is over the entire five year period. The press releases gives us cases, but a case might involve more than one or more firearms. It is not clear if a case would involve more than one homicide, but it is possible.
The vast majority of the cases of unlicensed firearms dealing, 58%, involved a mean of 2.3 firearms, the the number of firearms ranging from one to five.
There is little to indicate the investigation of the unlicensed sales prevented any homicides, or any violent crime. .....