The Gun Runners by Ralph Williams

The middle twentieth century was chosen as a source of supply after a careful survey of all factors pro and con. The gun runners did not want the mass weapons of their own day, they wanted selective weapons which could be used for private murder. In the mid-twentieth century, the level of technology was such that well-made and reliable weapons were available; and at the same time, social control was still sketchy enough to permit quiet procurement of such merchandise, if one knew how to go about it and was suitably financed.
The gun runners, two men and a woman, knew how to go about it, and they were suitably financed. The profits in their business were commensurate with the risks—which were not small.