Recommended would be "The New England Gun - the First 200 Years" by Merill Lindsay" printed by New Haven Press, New Haven Connecticut, in 1975. There is also "Vermont's Gunsmiths and Gunmakers to 1900" by Phillips and Tyler, published by Two @!*% Yankees, In.; Dorset, VT in 2000 as well as the two books on Underhammer Guns - the original by Herschel Logan in 1960 and the new book by Nich Chandler. Also chapter 3 (New England Militia Rifles) in Massachusetts Military Shoulder Arms 1784-1877 by George Moller by Mowbray Publishing, 1988.