Don't I wish their private papers could be found. Actually, some of the books of Ketland, Cotrill & Co do exist. This is one of the partnerships that TK Jr. was part of. They certainly dealt in guns but never with their name on them, hence they remain unknown to collectors. The walnut reference comes from purchases of vast swaths of walnut forest in Pennsylvania... the maple from the Liverpool shipping news. It's all late 18th, early 19th century. The export of timber is, however something that needs to be looked into in much greater detail. Walnut is not indigenous to Britain and was only introduced in the 15th century. It was always a "fruit tree" and therefore much too valuable to be cut simply for wood. Hardwood was, at the same time, the largest single export of the American colonies right through the early 19th century. We didn't export soft woods to England (aside from masts for the Royal Navy and likely some other specialty items)... the British bought that in Russia and the Baltic because it was cheaper and the shipping distances were much shorter.
The Ketland, Cotrill papers are in the Birmingham Library. They are the only surviving records of a B'ham merchant company trading with the United States in the late 18th century. Aside from telling us that they did trade in arms, they say little more as the entries are financial... "X amount for XX fowling pieces" etc.