Hi Dave,
DeWitt Bailey wrote several books that describe the British ordnance system during the 18th and early 19th centuries. It was a network of small, almost cottage, businesses that made different components on order from the Tower, and then the parts were stored until there was a warrant or demand for new muskets. When that happened, "setters up" in the Tower and Dublin Castle establishments assembled the components into finished muskets. They usuall used up older components first and when they were gone, used newer parts. Bailey lists private contractors making components as gun lock makers, gun barrel makers, brass founders, smallwork makers, and rammer/bayonet makers. Each of those contractors may have subcontracted to more specialized tradesmen such as lock polishers, gun spring makers, blade sharpeners, etc. The components were delivered to the Tower where gun barrel filers, rough stockers, setters up, and engravers assembled the muskets. According to Blackmore, a team of rough stockers could turn a walnut blank into a scraped gunstock in 10 hours.
dave