The Colt Navy revolver was out in 1861, and it would have been a 36 caliber , some Confederate agents purchased them before the war and Colt manufactured them til 1873. Hope it helps.
I have a confederate copy of a colt design, its a Leech and Rigdon 36 caliber navy that I carry in reenactments, its brass framed with an iron barrel because steel in southern states wasn't as abundant as northern states. Anything over 60 grains of powder would stretch a brass framed revolver in a good fight.