There is information regarding B&J Cooper in Swinney & Rowe's NYS Firearms Trade, Vol. 5, pp. 108-11. Much of the information comes from N.Y. City directories, indicating that their business, located in N.Y. City covers the time period from 1804-1820.
An advertisement they placed in the New York Herald, Nov. 7, 1804, states that they are "Gunmakers from Birmingham..." and that their shop, is located at 19 Partition Street.
Hope this is of some help.
sc