As of 2024, the FGC-9 is "by far" the world's most common 3-D printed gun, used by hobbyists, insurgents, militia members, terrorists, and drug traffickers in at least 15 countries.

[5] The gun's most prominent promoter is "Ivan The Troll," a man identified as John Elik in legal documents.

These changes and documentation honor the mutual influence of Defense Distributed's Liberator and Philip Luty's even earlier SMG designs.

[17] Due to the open-source nature of the FGC-9, there have been many packages released that alter the configuration, caliber, ergonomics, and other legally-restrictive qualities of the base-model firearm.

These are all available through a wide variety of channels, all with different levels of testing, and allow the end user to customize their weapon as needed.

The firearms hobbyist and instructor QueerArmorer created a version of the top rail for use in Myanmar by rebels fighting with limited access to optics in the Myanmar civil war, however its use was limited as another team from Deterrence Dispensed developed printable iron sights that allowed for more flexibility.

The following parts of the FGC-9 MkII have been modified to interface with the CZ Scorpion EVO magazine: The upper and lower receivers of the FGC-9 are fully 3D-printed, as are its pistol grip and stock.

[5] According to legal documents, Rajan Basra, a professor at International Centre for the Study of Radicalisation and a postdoctoral researcher in the Department of War Studies at King's College London, Nathan Mayer, a security researcher from the United States, and reporting from the New York Times, Ivan can be identified as John Elik, a 26-year-old licensed gunmaker in Illinois.

[3] In October 2023, a report published by the International Centre for the Study of Radicalisation and Political Violence named JStark1809 as Jacob Duygu, a German national born to Kurdish parents who arrived as refugees from Southeast Turkey in the 1990s.

The report claims he is the author of hundreds of anonymous internet posts, but does so using statistical inference from language patterns rather than direct evidence.

[70][71] According to the New York Times, from 2021-2024, the FGC-9 has been used by or found in possession of "paramilitaries in Northern Ireland, rebels in Myanmar and neo-Nazis in Spain", and has become a "staple" weapon of "the world's far-right extremists".

As of September 2024, an FGC-9 has not been linked to a homicide by law enforcement agencies, but this may be "because traditional forensic techniques are not always reliable on homemade weapons".