Allowing that no additional ‘smoking gun’ document has come to light, this article seeks to revisit some of the early literature on the cannon foundry established in Macao (c. 1627–1650) by Manuel Tavares Bocarro to expose gaps in our understanding as well as to encourage further research in this area. In line with recent historiography, the article acknowledges technological exchange in weaponry across Eurasia as opposed to an absolute European priority from the sixteenth century. As argued, this is amply demonstrated by the Portuguese–Ming China technology exchange such as contracted in Macao. As also demonstrated, the exchange was not confined to China but extended also to Japan and Vietnam under the southern Nguyễn dynasty at their request.