Abstract
3D-printed firearms, an emerging category of privately made firearms (PMF) produced beyond government control, have become increasingly prevalent due to technological advancements. They are now emerging as a cost-effective and reliable alternative to conventional firearms. Raised to public awareness following the 2013 release of the 3D-printed Liberator, these firearms are now more commonly encountered by police forces. This article analyses various reports involving 3D-printed firearms, reflecting the increasing encounters by law enforcement agencies. It examines 186 cases involving 3D-printed firearms, primarily from North America, Europe, and Oceania, highlighting a significant rise in incidents since 2021. These incidents include seizures, illicit uses, and online sales, with the firearms typically being hybrid models, Parts Kit Completions/Conversions (PKC), or firearm components such as auto sears. The study underscores the use of affordable equipment and materials for production, emphasizing the accessibility and potential risks of these firearms.

Introduction
Improvised and homemade firearms are available in various parts of the world. While they generally remain outnumbered by industrially produced firearms, trends in recent years point to the growing weight of improvised armaments in both conflict and crime settings. Ingenious blacksmiths in diverse regions including Pakistan, the Philippines, China and West Africa have produced homemade craft firearms for decades, the sophistication of which has increased over time. In Europe, blank-firing alarm handguns illegally converted to shoot lethal projectiles represent one of the main sources of illicit firearms. In the United States, so-called "privately made firearms" (PMF) account for a growing proportion of firearms used in crime: from 2016 to 2021, the "ATF received approximately 45,240 reports of suspected privately made firearms recovered by law enforcement, including in 692 homicide or attempted homicide investigations." Around the world, PMF encompass a variety of types, ranging from rudimentary and improvised designs to more sophisticated or craft-produced firearms, including among others zip guns, converted, modified, 3D-printed firearms, as well as 80% frames and lowers. The origins of these firearms can be traced back to the world wars, with their prominence growing towards the end of the last century and persisting to the present. Especially in recent years, the advent of 3D-printed firearms has emerged as a new phenomenon, gaining significant attention through all sorts of online media.

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